Application of Multisite Polypyridyl Ligands towards the Synthesis of Heterometallic Complexes

MISSING IMAGE

Material Information

Title:
Application of Multisite Polypyridyl Ligands towards the Synthesis of Heterometallic Complexes
Physical Description:
1 online resource (156 p.)
Language:
english
Creator:
Goforth, Sarah Kathryn
Publisher:
University of Florida
Place of Publication:
Gainesville, Fla.
Publication Date:

Thesis/Dissertation Information

Degree:
Doctorate ( Ph.D.)
Degree Grantor:
University of Florida
Degree Disciplines:
Chemistry
Committee Chair:
Mcelwee-White, Lisa Ann
Committee Members:
Talham, Daniel R
Castellano, Ronald K
Richardson, David E
Weaver, Jason F
Hagelin, Helena Ae

Subjects

Subjects / Keywords:
bipyridine -- dipicolylamine -- heterobimetallic -- polypyridyl -- site-selectivity
Chemistry -- Dissertations, Academic -- UF
Genre:
Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract:
Ligands containing linked dipicolylamine (dpa) and bipyridine (bpy) sites have been utilized as model systems for the study of selective metallation of polypyridyl ligands in the synthesis of heterobimetallic complexes.  The dpa site of these ligands has been observed to bind selectively to Zn2+, Pd2+,Pt2+, Co2+, and Cu2+ while the bpy site binds selectively to Rh+. These different selectivities for metal binding allow for preferential formation of singly metalated complexes.  Diamagnetic complexes were primarily characterized through NMR techniques, while EPR and IR techniques were used to identify the binding site of paramagnetic complexes containing Co2+ and Cu2+, IR results were also compared to those for previously synthesized diamagnetic Rh+, Zn2+, Pd2+ and Pt2+ complexes whose binding sites were primarily determined through NMR techniques.  Comparison of NMR, IR, and EPR results with those for model ligands was also used for confirmation of binding sites.  Addition of a second metal to the selectively prepared monometallic or homobimetallic complexes results in formation of heterometallic products.  Heterometallic Rh/Zn and Rh/Pd complexes were accessible by either order of metal addition.  A Rh/Pt complexes was also prepared by addition of Rh(COD)Cl2 to a homobimetallic Pt complex.  When dissolved in CD3OD, the Rh/Pd and Rh/Pt complexes exhibit H/D exchange at their dpa methylene site, but the monometallic Rh, Pt, or Pd complexes do not. Paramagnetic heterometallic complexes involving Cu2+were also prepared and were characterized through IR, EPR, mass spectrometry,and elemental analysis.  Since Rh and Cu have different site-selectivities, Rh/Cu complexes could be prepared by either order of metal addition. Conversely, different products could be produced by changing the order of metal addition in the synthesis of Pd/Cu heterometallic complexes since both of these metals preferentially bind at the dpa site.
General Note:
In the series University of Florida Digital Collections.
General Note:
Includes vita.
Bibliography:
Includes bibliographical references.
Source of Description:
Description based on online resource; title from PDF title page.
Source of Description:
This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility:
by Sarah Kathryn Goforth.
Thesis:
Thesis (Ph.D.)--University of Florida, 2013.
Local:
Adviser: Mcelwee-White, Lisa Ann.
Electronic Access:
RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2014-08-31

Record Information

Source Institution:
UFRGP
Rights Management:
Applicable rights reserved.
Classification:
lcc - LD1780 2013
System ID:
UFE0045828:00001


This item is only available as the following downloads:


Full Text

PAGE 1

1 APPLICATION OF MULTISITE POLYPYRIDYL LIGANDS TOWARDS THE SYNTHESIS OF HETEROMETALLIC COMPLEXES By SARAH KATHRYN GOFORTH A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT O F THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2013

PAGE 2

2 2013 Sarah Kathryn Goforth

PAGE 3

3 To my Mom who has always been my best friend and supporter

PAGE 4

4 ACKNOWLEDGMENTS First and foremost, I thank my advisor Lisa McElwee White for her endless support and encour agement. It has been an honor and a pleasur e to work under the supervision where I have been able to grow in my abilities as a chemist. For advice given and time spent, I a lso thank the other members of my committee: Dr. David E. Richardson, Dr. Daniel R. Talham, Dr. Ronald K. Castellano, Dr. Jason F. Weaver, and Dr. Helena Hagelin Weaver. I thank Dr. Khalil Abboud and Dan Denomme for solving the crystal structures presente d within this thesis. I am also grateful to Dr. Alexander Angerhofer for his contributions and guidance concerning the EPR spectroscopy presented. I thank all of the McElwee White group members who have helped me learn and grow throughout my graduate ca reer. Dr. Ma rie Correia served as my mentor and guided me through the waters (or hopefully lack thereof) of S c hlenk line and glove box chemistry. Dr. Phillip Shelton, Dr. Seth Dumbris, Jenny Johns, Ciera Gerack, Joseph Brannaka Kelsea Johnson Arijit Ko ley and many others were always available for meaningful scientific discussions. All have provided me with invaluable friendship throug hout my time here without which graduate school would have been very dreary. I am grateful for the excellent undergradu ate students whom I have had the opportunity to mento r including Lukas Hibell and Ma theus Birer. I am especially thankful to the talented and dedicated Richard Walroth who made many significant contributions to this project over the course of his undergra duate career. Finally, I thank my parents who have supported all my endeavors throughout my life and who have modeled for me the values and standards which I hold most dear

PAGE 5

5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 8 LIST OF FIGURES ................................ ................................ ................................ ........ 10 LIST OF ABBREVIATIONS ................................ ................................ ........................... 14 ABSTRACT ................................ ................................ ................................ ................... 16 CHAPTER 1 HETEROMETALLIC COMPLEXES: CATALYTIC APPLICATIONS AND SYNTHESIS ................................ ................................ ................................ ........... 18 Catalytic Applications ................................ ................................ .............................. 18 Augmentation of Reactivity and Selectivity ................................ ....................... 19 Differences in Products Formed ................................ ................................ ....... 20 Prevention of Side Reactio ns ................................ ................................ ........... 20 Multiple Reactions in a One Pot Synthesis ................................ ....................... 22 Design Principles for Heterometallic Catalysts ................................ ....................... 24 Synthetic Strategies for Production of Heterometallic Complexes .......................... 25 Examples of Post Metalation Bridging ................................ .............................. 25 Examples of Single Site Metalation of Pre Formed Ditopic Ligand and Relevant Site Selectivity Differentiators ................................ ........................ 27 Exploitation of hard/soft character of metals and binding sites .................. 30 Reactivity at one site ................................ ................................ .................. 31 Steric repulsion, coordination number, and chelation effects ..................... 35 2 SYNTHESIS OF Rh/Zn, Rh/Pd, and Rh/Pt COMPLEXES OF L1 AND L2 WITH NMR CHARACTERIZATION METHODS ................................ ............................... 39 Ligands L1 and L2 and Their Models ................................ ................................ ...... 39 Binding Site Determination by NMR ................................ ................................ ....... 40 Zn Complexes ................................ ................................ ................................ .. 41 Pd and Pt Complexes ................................ ................................ ....................... 44 Rh Complexes ................................ ................................ ................................ .. 45 Ru Complexes ................................ ................................ ................................ .. 48 Heterometallic Rh/Zn, Rh/Pd, and Rh/Pt Comple xes ................................ ............. 48 gHMBCAD NMR Studies ................................ ................................ ........................ 52 Hydrogen/Deuterium Exchange in Rh/Pd and Rh/Pt Complexes ........................... 60 Control Experiments with Monometallic, Homometallic, and Rh/Zn Complexes ................................ ................................ ................................ .... 61 Kinetic Studies ................................ ................................ ................................ .. 62

PAGE 6

6 Mechani stic Considerations and Implications ................................ ................... 64 Conclusions ................................ ................................ ................................ ............ 65 3 SYNTHESIS AND CHARACTERIZATION OF PARAMAGNETIC Co 2+ AND Cu 2+ COMPLEXES OF L1 AND L2 INCLUDING Rh/Cu, Pd/Cu, AND Pt/Cu HETEROMETALLIC COMPLEXES ................................ ................................ ........ 67 Cu and Co Binding Site Preferences for L1 and L2 ................................ ................ 68 I R Studies of Co and Cu Complexes ................................ ................................ ...... 69 EPR Studies of Cu Complexes ................................ ................................ ............... 73 Rh/Cu Complexes ................................ ................................ ................................ ... 79 Pd/Cu and Pt/Cu Complexes ................................ ................................ .................. 81 Conclusions ................................ ................................ ................................ ............ 83 4 ELECTROCHEMICAL STUDIES OF L1 AND L2 COMPLEXES ............................ 85 Background on Heterobimetallic Electrocatalysts for Alcohol Oxidation with Application to Direct Alcohol Fuel Cells ................................ ............................... 85 Considerations Invo lving Metal Selection ................................ ............................... 88 Cyclic Voltammetry of Complexes of L1 and L2 ................................ ..................... 89 Rh/Zn L1 Complex ................................ ................................ ........................... 90 Rh/Pd and Rh/Pt Complexes ................................ ................................ ............ 92 Rh/Cu L1 Complex ................................ ................................ ........................... 97 Bulk Electrolysis of Heptanal with Rh L1 Complex ................................ ................. 98 Conclusions ................................ ................................ ................................ ............ 99 5 ATTEMPTED SYNTHESES INVOLVING AN ALTERNATIVE MULTISITE POLYPYRIDYL LIGAND ................................ ................................ ....................... 102 Bridging Ligand Design and Synthetic Scheme ................................ .................... 102 Metal Binding Studies ................................ ................................ ........................... 103 Conclusion ................................ ................................ ................................ ............ 107 6 EXPERIMENTAL SECTION ................................ ................................ ................. 110 General Considerations ................................ ................................ ........................ 110 Synthetic Proced ures ................................ ................................ ............................ 111 Syntheses of Ligands ................................ ................................ ..................... 11 1 Syntheses of Model Complexes ................................ ................................ ..... 114 Syntheses of Monometallic and Homobimetallic Complexes of L1 and L2 .... 116 Syntheses of Diamagnetic Heterometallic Complexes of L1 and L2 .............. 122 Syntheses of Paramagnetic Heterometallic Complexes of L1 and L2 ............ 126 Synthesis of L3 Complexes ................................ ................................ ............ 130 Kinetic Studies of H/D Exchange in Rh/Pd and Rh/Pt Complexes ........................ 131 Electrochemical Experiments ................................ ................................ ................ 132 IR Studies ................................ ................................ ................................ ............. 132 EPR Studies ................................ ................................ ................................ ......... 133 X ray Crystallography Structure Determination ................................ ..................... 133

PAGE 7

7 APPENDIX : X RAY CRYSTAL STRUCTU RE BOND LENGTHS AND ANGLES ....... 135 LIST OF REFERENCES ................................ ................................ ............................. 148 BIOGRAPHICAL SKETCH ................................ ................................ .......................... 156

PAGE 8

8 LIST OF TABLES T able page 2 1 Attempts to bind Ru to dpa, L1, and Rh bound L1 complex 50 ......................... 48 2 2 General splitting patterns for L1 and L2 compounds. ................................ ......... 53 2 3 Chemical shift assignments for ligands L1, L2, and L2. ................................ ...... 55 2 4 Chemical shift assignments for ligands L1, L 2, and L2. ................................ ...... 55 2 5 Chemical shift assignments for Zn, Pd, and Pt complexes of L1, L2, and L2'. .. 56 2 6 Chemical shift assignments for Zn, Pd, and Pt complexes of L1, L2, and L2'. .. 57 2 7 Chemical shift assignments for Rh, Rh/Zn, Rh/Pd, and Rh/Pt complexes of bpy0, L1, L2, and L2'. ................................ ................................ ......................... 58 2 8 Chemical shift assignments for Rh, Rh/Zn, Rh/Pd, and Rh/Pt complexes of bpy0, L1, L2, and L2'. ................................ ................................ ......................... 59 2 9 Summary of H/D exchange experiments. ................................ ........................... 64 3 1 Vibrational frequencies between 1420 cm 1 and 1620 cm 1 of ligands and of reaction mixtures of ligands with sub stoichiometric amounts of various metal sources. ................................ ................................ ................................ .............. 70 3 2 Vibrational frequencies between 1420 cm 1 and 1620 cm 1 of products completely metalated in either the dpa or bpy site(s) in the given ligand. ........... 71 3 3 Crystal data and structure refinement for complex 64 ................................ ....... 75 3 4 Selected bond lengths () and bond angles () for complex 64 ......................... 77 3 5 EPR data obtai ned from mixtures of Cu(OTf) 2 and various ligands at 20 K. a ..... 77 3 6 EPR data for Rh/Cu complexes in MeOH at 20 K. ................................ ............. 79 3 7 EPR data obtained for Pd/Cu and Pt/Cu complexes in 50:50 DMSO/H 2 O at 20 K. ................................ ................................ ................................ ................... 82 5 1 Metal binding experiments involving L3. ................................ ........................... 104 5 2 Crysta l data and structure refinement for L3 complexes 72 73 and 75 a ........ 108 5 3 Selected bond lengths () and bond angles () for complex 72 a ..................... 109 5 4 Selected bond lengths () and bond angles () for complex 73 ....................... 109

PAGE 9

9 5 5 Selected bond lengths () and bond angles () for complex 75 a ..................... 109 A 1 Bond lengths () for complex 64 ................................ ................................ ..... 136 A 2 Bond angles () for complex 64 ................................ ................................ ....... 138 A 3 Bond lengths () for complex 72 ................................ ................................ ..... 142 A 4 Bond angles () for complex 72 ................................ ................................ ....... 143 A 5 Bond lengths () for complex 73 ................................ ................................ ..... 144 A 6 Bond angles () for complex 73 ................................ ................................ ....... 145 A 7 Bond lengths () for complex 75 ................................ ................................ ..... 147 A 8 Bond a ngles () for complex 75 ................................ ................................ ....... 147

PAGE 10

10 LIST OF FIGURES Figure page 1 1 Example s of heterobimetallic catalysts for hydroformylation. ............................. 19 1 2 Heterobimetallic ethylene polymerization catalysts. ................................ ........... 21 1 3 Cr/Ni catalysts for coupling of aryl halides with aldehydes. ................................ 21 1 4 Tandem reactions catalyzed by heterobimetallic complexes. ............................. 23 1 5 Schematic of post metalation bridging approach. ................................ ............... 26 1 6 Example of Route A of post metalation tethering approach. .............................. 26 1 7 The common dppm ligand used as a platform for heterometallic complexes ( 21 and 22 ) and u nintentionally bound through both phosphines to the same metal center ( 23 ). ................................ ................................ ............................... 27 1 8 Homoditopic ligand for the preparation of heterometallic complexes. ................. 28 1 9 Some possible pathways of product formation in site selectivity approach.. ...... 29 1 10 Selective preparation of O,O and N,N monometallic complexes, but with only on e route to heterobimetallic complex. ................................ ....................... 30 1 11 Examples of heterometallic complexes formed based on hard/soft site selectivity. ................................ ................................ ................................ ........... 31 1 12 N H activation strategy for monometallic complex formation. ............................. 32 1 13 Methodology described by Akita and coworkers for their production of a library of isomeric heterobimetallic complexes with switched metal arrangement. ................................ ................................ ................................ ...... 33 1 14 Different site selectivity from absence or presence of base. .............................. 33 1 15 Synthesis of heter ometallic complexes 35 and 36 ................................ ............. 34 1 16 Synthesis of heterometallic complexes 37 and 38 ................................ ............. 34 1 17 Selective addition by transmetal ation. ................................ ................................ 35 1 18 Alternate route towards production of Pt/Cu complexes bridged by pyrazolate ligands. ................................ ................................ ................................ ............... 36 1 19 Selectively prepared monometallic Ir complexes bearing free dpa ligands for subsequent coordination. ................................ ................................ ................... 37

PAGE 11

11 1 20 Ligands L1 and L2. ................................ ................................ ............................. 37 2 1 Model ligands of L1 and L2. ................................ ................................ ................ 39 2 2 Zn, Pt, and Pd complexes 44 49 ................................ ................................ ....... 40 2 3 Rh complexes of L1 and L2. ................................ ................................ ............... 40 2 4 1 H NMR comparison of dpa, bpy1, L1 and 41 ................................ ................... 42 2 5 Labeling system used throughout this chapter for protons and carbons of L1 and L2 complexes. ................................ ................................ ............................. 42 2 6 Methylene region of the 1 H NMR spectra of 41 42 and 43 .............................. 43 2 7 Homobimetallic and homotrimetallic complexes 52 and 53 ............................... 45 2 8 Comparison of the aromatic region of the 1 H NMR spectra of complex 47 and mixtures 46 / 52 and 47 / 53 ................................ ................................ .................. 46 2 9 1 H NMR comparison of L1 and 50 ................................ ................................ ..... 47 2 10 1 H NMR comparison of bpy0 and 54 ................................ ................................ 47 2 11 Heterometallic complexes 55 60 ................................ ................................ ....... 49 2 12 Aromatic region of the 1 H NMR spectrum of complex 55 with that of complex 41 for comparison. ................................ ................................ .............................. 50 2 13 Complementary routes for the synthesis of 58 ................................ .................. 51 2 14 Complementary routes for the synthesis of 59 ................................ .................. 51 2 15 Assigned 1 H and 13 C NMR shifts of Rh/Zn complex 55 ................................ ..... 53 2 16 Aryl region of the gHMBCAD spectrum of Rh/Zn complex 55 ........................... 54 2 17 H/D exchange reaction observed for complex 60 in CD 3 OD.. ............................ 60 2 18 1 H NMR spectra of 60 in CD 3 OD at 25C as one of the dpa methylene proton s is exchanged with deuterium. ................................ ............................... 61 2 19 Plots of ln[ 60 ] t versus time for two so lutions with initial concentrations of 5.2 mM and 2.4 mM. ................................ ................................ ................................ 63 2 20 Two 180 views of a Spartan model of binding between Rh center and dpa methylene proton in 58 ................................ ................................ ...................... 66

PAGE 12

12 2 21 ChemDraw representations of possible interactions between the Rh center and dpa methylene protons of 58 .. ................................ ................................ ..... 66 3 1 IR study of the addition of CoCl 2 to L 1, L2, and L2'. ................................ ........... 72 3 2 Expansion of the 1350 cm 1 to 1700 cm 1 region of the IR spectra of L1, L2, L1', L2', and L2'' bound to PdCl, CoCl 2 or Cu(OTf) 2 ................................ .......... 73 3 3 Thermal ellipsoids diagram of complex 64 ................................ ....................... 74 3 4 Glass EPR spectra of Cu, Pd/Cu, and Pt/Cu complexes in 50:50 DMSO/H 2 O at 20 K. ................................ ................................ ................................ ............... 76 3 5 EPR spectra for 2:1 mixtures of Cu(OTf) 2 and L1. ................................ ............. 78 3 6 Complementary routes for the synthesis of 65 ................................ .................. 80 3 7 IR spectra of the samples obtained from different routes of synthesizing 65 and 66 ................................ ................................ ................................ ............... 80 3 8 EPR spectra of the samples obtained from different routes of synthesizing 65 an d 66 ................................ ................................ ................................ ............... 81 3 9 Reaction of Pd and Pt complexes with Cu(OTf) 2 ................................ ............... 83 3 10 Synthesis of Pd/Cu complex 71 with bpy bound Pd and dpa boun d Cu. ............ 83 4 1 Reactions in the two alternative pathways for the complete 6 e oxidation of methanol to CO 2 ................................ ................................ ................................ 85 4 2 Selected react ions along pathways for the oxidation of ethanol to CO 2 ............ 86 4 3 Examples of dppm bridged complexes along with examples of their electrochemical studies. ................................ ................................ ..................... 87 4 4 Examples of stoichiometric and catalytic decarbonylation using Rh compounds. ................................ ................................ ................................ ........ 89 4 5 Cyclic voltammogram of Rh/Zn complex 55 with those of 54 41 and L2 for com parison ; performed in CH 3 CN/TBAH. ................................ ......................... 91 4 6 Cyclic voltammetry of L1 and its Zn ( 41 ), crude Rh ( 50 ),and Rh/Zn ( 55 ) complexes in DCE/TBAT ................................ ................................ .................... 92 4 7 Cyclic voltammogram of Rh/Pd L1 complex 58 and the effect of EtOH addition; performed in DCE/TBABF 4 ................................ ................................ .. 93 4 8 Cyclic voltammograms of Rh/Pd complexes 58 and 59 with those of [Pd(dp a)Cl]Cl, 54 and L2 for comparison ; performed in CH 3 CN/TBAH. .......... 95

PAGE 13

13 4 9 Cyclic voltammogram of Rh/Pd L1 complex 58 and the effect of EtOH addition; performed in CH 3 CN/TBAH. ................................ ................................ 96 4 10 Cyclic voltammetry of Rh/Pd L2 complex 59 and Pd L2 complex 47 complexes of L2; performed in MeOH/ TBABF 4 ................................ .................. 97 4 11 Cyclic voltammogram of Rh/Pt L2 complex 60 and the effect of EtOH addition; performed in DMF/TBAH. ................................ ................................ ..... 97 4 12 Cyclic voltammograms of Rh/Cu complex 65 with additional voltammograms for comparison ; performed in CH 3 CN/TBAH. .. ................................ .................... 99 4 13 Sampling of cyclic voltammograms of Rh/Cu complex 65 in CH 3 CN/TBAH after various cycles ................................ ................................ ......................... 101 4 14 Pentane formation ob served in the bulk electrolysis of hexanal in the presence of 50 ................................ ................................ ................................ 101 5 1 The multisite ligand L3.. ................................ ................................ .................... 102 5 2 Previously reported monometallic and homobimetallic Cu complexes of L3. ... 102 5 3 Scheme for utilization of L3 as a platform for heterometallic complexes. ......... 103 5 4 Thermal ellipsoids diagram of Cu L3 complex 72 ................................ ........... 105 5 5 Thermal ellipsoids diagram of Cu L3 complex 73 ................................ ........... 1 05 5 6 T hermal ellipsoids diagram of Cu L3 complex 74 ................................ ........... 106 5 7 Thermal ellipsoids diagram of Co L3 complex 75 .. ................................ ........... 107 A 1 Crystal structu re drawings of complex 64 with atom labels. ............................. 135

PAGE 14

14 LIST OF ABBREVIATIONS bpy bipyridine Cp cyclopentadienyl ligand Cp* 1,2,3,4,5 pentamethylcyclopentadien yl ligand COD 1,5 cyclooctadiene CV cyclic voltammetry DCE 1,2 dichloro ethane DCM dichloromethane DMF dimethylformamide DMSO dimethylsulfoxide dpa dipicolylamine dppm 1,1 bis( diphenylphosphino ) methane EtOAc ethyl acetate EtOH ethanol Et 2 O diethyl ether ESI electrospray ionization FT IR Fourier transform infrared spectroscopy GC gas chromatography gHMBC AD gradient selected heteronuclear multiple bond c orrelation using adiabatic pulses MeOH methanol MS mass spectrometry NHC N heterocyclic carbe ne NHE normal hydrogen electrode NMR nuclear magnetic resonance spectroscopy OTf trifl uoromethanesulfonate

PAGE 15

15 phen phenanthroline TBABF 4 tetrabutylammonium tetrafluoroborate TBAH tetrabutylammonium hexafluorophosphate TBAT tetrabutylammonium trifluoromethanesulfonate THF tetrahydrofuran TOF time of flight TON turnover number

PAGE 16

16 Abstract of Disse rtation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy APPLICATION OF MULTISITE POLYPYRIDYL LIGANDS TOWARDS THE SYNTHESIS OF HETEROMETALLIC CO MPLEXES By Sarah Kathryn Goforth August 2013 Chair: Lisa McElwee White Major: Chemistry Ligands containing linked dipicolylamine (dpa) and bipyridine (bpy) sites have been utilized as model systems for the study of selective meta lation of polypyridyl li gands in the synthesis of heterobimetallic complexes. The dpa site of the se ligands has been observed to bind selectively to Zn 2+ Pd 2+ Pt 2+ Co 2+ and Cu 2+ while the bpy site binds selectively to Rh + These different selectivities for metal binding all ow for prefer ential formation of singly meta lated complexes. Diamagnetic complexes were primarily charac terized through NMR techniques, while EPR and IR techniques were used to identify the binding site of paramagnetic complexes containing Co 2+ and Cu 2+ IR results were also compared to those for previously synthesized diamagnetic Rh + Zn 2+ Pd 2+ and Pt 2+ complexes whose binding sites were primarily determined through NMR techniques. Comparison s of NMR, IR, and EPR results with those for model ligands w as also used for confirmation of binding sites Addition of a second metal to the selectively prepared monometallic or homobimetallic complexes results in formation of heterometallic products. Heterometallic Rh/Zn and Rh/Pd complexes were accessible by either order of metal addition. A Rh/Pt complex was also prepared by addition of [Rh(COD)Cl] 2 to a

PAGE 17

17 homobimetallic Pt complex. When dissolved in CD 3 OD, the Rh/Pd and Rh/Pt complexes exhibit H/D exchange at their dpa methylene site, but the monometallic R h Pt, or Pd complexes do not. Paramagnetic heterometallic complexes involving Cu 2+ were also prepared and were characterized through IR, EPR, mass spectrometry, and elemental analysis. Since Rh and Cu have different site selectivities, Rh/Cu complexes cou ld be prepared by either order of metal addition. Conversely, different products could be produced by changing the order of metal addition in the synthesis of Pd/Cu heterometallic complexes since both of these metals preferentially bind at the dpa site.

PAGE 18

18 CHAPTER 1 HETEROMETALLIC COMPLEXES : CATALYTIC APPLICATIONS AND SYNTHESIS Catalytic Application s The use of bi metallic complexes as catalysts has arisen as a potentially useful motif in organometallic catalysis. 1 7 The rationale behind the use of these catalysts is that the two different metals involved can interact cooperatively to achieve new reactivity th at is not possible with one metal center. In some cases, each metal is an active site for different steps in the reaction. In others, the connection between the two metals through one or more bridging ligands alters the electronic properties of the activ e metal site. H eterobi metallic catalysts have been utilized in many reaction types including carbonylation, 8 9 C C coupling, 10 12 alcohol oxidation, 13 15 asymmetric catalysis, 16 17 hydroformylation 18 23 and ethylene polymerizatio n. 24 26 Heterometallic complexes have also been successful in the area of tandem catalysis. 27 29 For example, Ir/Pd complexes were found to catalyze Suzuki coupling/transfer hydrogenations 30 and Cu/Pd catalysts were employed for tandem click/Sonogashira reactions 31 In all cases, the hetero bi metallics are compared to relevant monometallic analogues and/or mixtures of monometallic analogues or even homobimetallic analogues. Among the adv antages often displayed by the covalently bound heterometallic systems are (1) higher activities, (2) better yields/conversions, (3) enhanced product selectivity, (4) formation of different products, and (5) ability to perform new reactions or combinations of reactions. When the proximity of these two metals allows for one such cooperative effect to be observed, the mechanistic causes can be considered and applied to future studies. The following sections of this chapter will give several examples regardi ng each of these possible

PAGE 19

19 advantages of hetero bi metallic complexes o ver their monometallic and homo bi metallic analogues. Augmentation of Reactivity and Selectivity Various h eterobimetallic catalysts have been found to enhance both the reactivity and the s electivity for the hydroformylation of olefins (Figure 1 1) 20 21 23 Rh/Zr complex 1 was found to exhibit marginally higher regioselectivity for the linear aldehyde product along with higher activities when compared to the Rh precursor alone. 21 The origin of the cooperativity is proposed to arise from mediation of the electron density at the Rh reactive site by the Zr center. Smith, et al. proposed two possible mechanisms for the enhanced linear selectivity exhibited by their Rh/Ru complex 2 ( n nonan a l: 2 methyloctanal ratio between 8 :1 and 9 :1 ) when compared to [RhCl(CO) 2 ] 2 ( n nonan a l: 2 methyloctanal ratio of 1 :1 ) 22 23 In one possible mechanism, the Ru center acts as a labile ligand allowing for facile oxidative addition at the Rh center. The alternative route for the observed cooperativity involves dinuclear oxidative addition of H 2 across both metal centers In contrast, Hidai proposes the final production of aldehydes in his Co 2 (CO) 8 Ru 3 (CO) 12 systems to result from a dinuclear reductive elimination from cobalt acyls and ruthenium hydrides. 20 Figure 1 1 Example s of heterobimetallic catalysts for hydroformylation. 21 23

PAGE 20

20 Differences in Products Formed Osakada and coworkers reported a series of Zr/Pd, Zr/Co, and Zr/Ni complexes as active catalysts for eth ylen e polymerization (Figure 1 2 ). 24 The activities of the heterometallic complexes 7 9 were of the same order of magnitude as those of the monometallic Zr, Co, and Ni complexes 3 6 with the highest a ctivity bei ng exhibited by the monometallic Zr complex. However, the structure and properties of the polyethylene products produced by utilization of these catalysts were found to be dependent upon the type of late transition metal employed. The monometa llic Zr complex 3 yielded polymer with no branching. The Zr/Ni complex 9 by itself was found to catalyze the formation of polymer with significant methyl, ethyl, and other alkyl branching leading to lower melting points for these products. In contrast, the same conditions for ethylene polymerization utilizing mixtures of monometallic compounds 3 and 6 as catalyst result ed in polyethylene with almost no methyl and ethyl branches. The Zr/Co catalyst 8 also induced slightly more ethyl branched product than a mixture of its corr esponding mononuclear catalysts 3 and 5 and it exhibited almost double the activity. The proposed branching mechanism involves primary polymer growth at the Zr center with oligomer growth at the second metal center. The efficiency of the incorporation of these oligomers into the polymer is enhanced by the pro ximity of the two metal centers A crystal structure of the Zr/Co complex 8 revealed this distance to be ca 9.1 Prevention of Side Reactions Ni/Cr complexes based on teth ered bipyr idine/bipyridine and bipyridine / phenanthroline ligands (Figure 1 3 ) were reported as active catalyst s for coupling vinyl hal ides with aldehydes. 32 Such Ni/Cr catalyzed couplings were known previously for

PAGE 21

21 separate Ni and Cr cocatalysts and had found utility i n late stage multistep syntheses as they exhibit high functional group tolerance. One problem with such systems, however, is that excess nucleophile (1.5 to 2.0 equiv) is necessary to avoid production of the homocoupling product which can be produced from the Ni(II) viny l species prior to a transmetal ation of this species to Cr(II). Tethering the two metal sites together was found to be an efficient means of suppressing the homocoupling side reaction by instead promoting the transmeta lation step. The Ni/ Cr catalysts 10 and 1 1 were able to successfully mediate several coupling reactions with a wide range of substrates using only 1.1 equiv of nucleophile. Figure 1 2 Heterobimetallic ethylen e polymerization catalysts. 24 Figure 1 3 Cr/Ni catalysts for coupling of aryl halides with aldehydes. 32

PAGE 22

22 Multiple Reactions in a One Pot Synthesis One pot procedures for the catal ysis of multiple reactions are desirable from both environmental and economic standpoints and have been the subject of interest in the literature. 33 The linkage of two metals capable of catalyzing different reactions would seem ideally suited for such processe s, thus making h eterometall ic complexes promising as catalyst candidates. Peris and coworkers have described a series of bimetallic catalysts 12 17 based on the 1,2,4 trimethyltriazo lyl diylidene ligand (ditz) and have tested them as catalysts for multiple tandem reactions (Figure 1 4) 28 30 34 The individual steps in the overall tandem r eactions were chosen such that each was specifically promoted by one of the different metals in the complex. The catalytic results of the heterobimetallic complexes tested were then compared to those of its homobimetallic analogues and their mixtu res. For the tandem dehalogenation/transfer hydrogenations of haloacetophenones (Tandem Reaction A) product C forms exclusively from catalysis by Ir/Pd complex 12 while the intermediate products A and B form from catalysis by homobimetallic complexes 15 and 17 respectively These intermediates are expecte d based on the catalyst design for dehalogenation at the Pd center and ketone transfer hydrogenation at the Ir center. As more convincing confirmation of a cooperative effect between the two metals i n complex 12 for this tandem process, a 1:1 mixture of these two homobimetallic complexes under the same conditions leads to only 25% conversion to product C with 72% conversion to product A Similar cooperative effects were observed f or the Suzuki coupli ngs combined with either transfer hyd alkylations (Tandem Reaction B) and for the sequential cyclization of 2 ( o aminophenyl)ethanol followed by addition of an alkynyl alcohol (Tandem Reaction C)

PAGE 23

23 Tandem Reaction A: Tandem Reaction B: Tandem Reaction C: Figure 1 4 T andem reactions catalyzed by heterobimetallic complexes. 28 30 34

PAGE 24

24 Design Principles for Heterometallic C atalyst s When choosing appropriate bridging and ancillary ligands for heterobimetallic targets, man y of the same overarching design optimization variabl es for general homogeneous transition metal catalysts will apply: ligand flexibility, steric constraints placed around metals (i.e. substrate binding sites), coordination environment of the metals, avail ability of an open coordination site for substrate binding and electron count. The primary additional design principles for enhancing heterometallic cooperativity are to maximize the extent of electronic communication between the metals as well as their proximity to one another. Direct electronic contact between metal sites is often achieved through conjugated bridging ligands such as phendiones, pyrimidine and similar ligands 35 36 but can also be achieved through small bridges such as halides or carbonyls or through direct metal metal bonds. It should be noted that s uch direct through bond electron ic communication between metals is not critical for the production of a cooperative effect. As long as the two metals are in close enough through space proximity they may be able to react with the same substrate or simultaneously activate two reactants. The optimum distance for such interactions is around 3.5 to 6 1 Due to the direct electronic communication discussed, one may be tempted to rely solely on small bridges or metal metal bonds. While it is true that such ligands alone may serve as the only connection s betw een the two metals in some heterometallic catalysts they tend to be less stable than would be desired as these bridging ligands and metal bonds are labile 37 39 For instance, i Rh/Ru hydroformylation catalyst 2 which contains two bridging carbonyls and a metal metal bond, both proposed hydroformylation mechanisms involve multiple ste ps in

PAGE 25

25 which the only remaining link between the two metals is the bridging diphosphine ligand. 23 Generally in order to produce stable and well defined bimetallic complexes for use in catalysis, an appropriate bridging (or dinucleating) ligand must be selected. 40 Synthetic Strategies for Production of Heterometallic Complexes Though heterobi metallic complexes have proven to be useful in the field of catalysis their synthesis can be challenging. Strategies for t he synthesis of well defined heterometallic complexes in which the metals are connected by a major bridging ligand involve one of two major approaches: metalation prior to the formation of the bridge within the ligand and metalation following the formation of the complete bridging ligand. Examples of Post Metalation Bridging The first strategy for synthesis of heterometallic complexes involves ligands that initially contain only one metal binding site, B 1 but also contain functionality that can be used t o tether a second metal binding site, B 2 (Figure 1 5 ). F ormation of Ru/Mn complex 20 is an example of this approach via route A in which the Ru is first bound to the bpy site of a monobromomethyl 2,2 bipyridine moiety (Figure 1 6) 41 Subsequently, the dpa site is added by substitution with the bromo substituent of 18 followed by Mn coordination Similar methods were employed in the formation of another Ru bpy complex with a free dpa site for later metal coordination 42 In an alternative route B, both metal centers may be bound to their respectiv e binding sites prior to the tethering step. offer an excellent example with heterometallic complexes being formed via s elective cross metathesis between a zirconocene derivative modified with an allyl subs tituent and Pd, Co, and Ni complexes of a ligand bearing an acrylate moiety (Figure 1 2). 24

PAGE 26

26 Figure 1 5 Schematic of post metalation bridging approach. Figure 1 6 Example of Route A of post metalation tethering approach. 41 The major advantage of this approach is that no care needs to be taken towards designing each site for selectivity towards one metal or another. Thus, unless the metals are able to exchange with each other after being bound to their respective sites, the formation of homobimetallic complexes is avoided. Such a technique is less ideal when M 1 and its complexes are particularly expensive and/or air sensitive as carrying the metal through an extra synthetic step leads to lower overall utilization of initial metal source and to extra time and care during synthetic procedures. Another problem which may potentially arise when using this approach is incompatibility of the metal sources with the functional groups employed for tethering as has been encountered by this author Specifically, reacting [Rh(COD)Cl] 2 with a bromomethyl substituted bipyridine

PAGE 27

27 led to a complex mixture of products due to reactivity of the bromomethyl group with t he metal. 43 If instead the reaction with [Rh(COD)Cl] 2 was performed after a substitution reaction to replace the Br with the second binding site, the metal addition occurred exclusively at the bipyridine site as will be discussed in Chapter 2. Examples of Single Site Metalation of Pre Formed Ditopic Ligand and Relevant Site Selectivity Differentiators The second general approach involves beginning with the entire ligand containing both metal binding sites covale ntly l inked prior to metal addition. While this is the most common approach encountered, more care must be taken to avoid formation of homobimetallic complexes Another issue which may arise with these pre formed ligands is occupation of both sites by th e same metal center. For instance, the well known dppm dinucleating ligands used as the basis for many heterobimetallic complexes can sometimes form complexes in which both phosphine units are bound to the first added metal thus leaving no place in the intended bridge for the second metal to bind (Figure 1 7) 44 Figure 1 7 The common dppm ligand used as a platform for heterometallic complexes ( 21 and 22 ) and unintentionally bound through both phosphines to the same metal center ( 23 ) 44 Generally, the first metal addition to selectively form monometallic product is the most difficult. However, performing this step successfully does not guarantee attainment of the targeted heterometallics after the second metal additio n The ligand

PAGE 28

28 24 was used to form monometallic complexes of both Rh + and Ir + (Figure 1 8) 39 However, addition of 1 equiv of [Rh(COD)] 2 to the several forms of the Ir + monometallic complex under several variations of solvent and temperature always resulted in formation of a statistical mixture of 25:25:50 of homobimetallic Ir + complex to homobimetallic Rh + complex to heterobimetallic Rh + /Ir + complex. The authors were unable to separate the desired heterometallic complex from the mixture. No results were reported for the addition of Ir + starting material to the Rh + monometallic complex. Figure 1 8 H omoditop ic ligand for the preparation of heterometallic complexes. 3 9 When compared to the post metalation bridging strategy described previously this approach does involve the greate r risk for formation of such homometallic analogues of the desired targets. This risk can be abated by employment of heteroditopic liga nds whose sites have different binding affinities for different metals or whose metal binding can be controlled in a stepwise fashion 45 50 If the first incoming metal prefers one site over the other, formation of a specific monometallic complex is favored while the other site should remain available for further metal binding M ultiple strategies exist for diff erentiating the two sites in the s e heteroditopic liga nds as will be discussed in the ne xt several sections. Sometimes one of the sites is generally preferred by most metals, and other times each site favors different sets of metals. In the first case, two different products have the potential to be selecti vely formed so long

PAGE 29

29 as excha nge is not observed (Figure 1 9A ). 51 In the latter case, only one product should form as a result of the intrinsic bi nding preferences of the two metals being employed (Figure 1 9B ). Figure 1 9 Some possible pathways of product formation in site selectivity approach. A) Pathways involving metals with id entical site selectivities. B) Pathways involving metals with opposite site selectivities. Because either order of metal addition may be successful when the two metals have different binding preferences, synthetic flexibility is present through the two av ailable routes. For instance, though preparation of heterometallic Ir/Pd complex 25 cannot be formed via addition of Ir 3+ starting material to the monometallic Pd 2+ precursor 26 addition of Pd 2+ sources to the Ir 3+ monometallic precursor 27 does lead to successful formation of the heterometallic complex (Figure 1 10). 52 An additional possibility exists for concurrent addition of both metals in one step provided the two

PAGE 30

30 required reactions are compatible with ea ch other As exchange of metals is unlikely if the intrinsic selectivities are different one can also avoid situations in which homobimetallics are formed even after successful synthesis of monometallics as was observed for ligand 24 Figure 1 10 Selective preparation of O,O and N,N monometallic complexes, but with only one route to heterobimetallic complex. 52 Exploitation of h ard/ s oft charact er of metals and binding sites Incorporation of sites with varying hardness and softness is one of the more common and simple methods of differentiating binding sites in heteroditopic ligands 53 Wagner Ir/Pd complex whose synthesis was described i n Figure 1 10 is an example. The heteroditopic ligand displays O,O' selectivity for Ir 3+ and Ru 2+ sources and N,N' selectivity for Pd 2+ sources. 52 Synthesis of the asymmetric hydroformylation catalyst 28 relies on in i tial addition of Ti 4+ to the hard N,N',O,O' site followed by coordination of Rh + to the soft P,P' site (Figure 1 11) 17 Similarly, the two metal binding sites in complexes 29 and 3 0 are differentiated by th e relative softness of phosphor us versus nitrogen. 54 55 In the case of 3 0 initial addition of (CH 3 ) 2 Pd(tmeda) leads to formation of a dimer 3 1 involving head to tail binding of two ligand s to two Pd centers. Subsequent addition of CuI and H 2 O in oxygen atmosphere eventually leads to installation of a Cu 2+ center at the softer N,N' site. The Ph 2 PCH 2 ligand of Rh/Zr catalyst 1 is another example of a

PAGE 31

31 hard/soft platform for the selective production of a heterometallic complex containing both early and late transition metals. 21 Figure 1 11 Examples of heterometallic complexes formed based on hard/soft site selectivity. 17 54 55 Reactivity at one site In some cases, the incorporation of the typical soft phosphine s ites may be unsuitable for the catalytic processes intended for the heterobimetallic targets, and other techniques must be used for the differentiation of the binding sites. For instance, in contrast to the P P ', N N ligand of compound 29 Chen and coworke rs have reported a desire to produce Pt Cu complex es with an all N dinucleating ligand in order to take advantage of C H activation processes known to be mediated by N coordinated platinum while coupling such processes with the rich chemistry of Cu catalys ts 56 In one attempt, they based their strategy upon known N H activation of related

PAGE 32

32 2 (N arylimino) pyrroles by [(Me 2 S)PtMe 2 ] 2 and successfully produced monometallic complex 3 2 containing an empty coordination site for futur e Cu complexation ( Figure 1 12 ) The related ligand N,N' bis[(2 diphenylphosphino)phenyl]formamidine, which contains a central formamidine with pe n dant phosphine groups also produce s monometallic complexes from activation of the N H bond 57 58 These compounds can be further reacted with a variety of other metals to produce heterobimetallic complexes. Figure 1 12 N H activation strategy for monometallic complex formation. 56 Conversely, Rh, Ir, and Pd sources were found to selectively bind to the nitrogen with an already free lone pair in re lated pyrazolate ligands (Figure 1 13). 51 59 Addition of the second metal with base allowed for metal uptake a t the second site. Akita and coworkers were able to employ this methodology for the formation of a library of isomeric heterobimetallic complexes with switched metal arrangements. By similar design, monometallic complex 3 3 was selectively formed upon sim ple reaction of the multisite ligand with Pd(COD)(Me)Cl, while preferential binding primarily at the bis(quinolinyl)amide (BQA) was observed when introducing base concurrently with metal addition to form complex 3 4 (Figure 1 14) 45

PAGE 33

33 Figure 1 13 Methodology described by Akita and coworkers for their production of a library of isomeric heterobimetallic complexe s with switched metal arrangement. 51 59 Figure 1 14 Different site selectivity from absence or presence of base. 45 Ligand designs which involve the inclusion of an imidazolium salt as one arm of a heteroditopic ligan d have also been successful for the selective preparation of heterometallic complexes. Nickel acetate was found to induce metal binding exclusively at a S c hiff base site in a ligand which also contained an imidazolium salt. S ubsequent in situ generation of the Ag NHC and transmetal ation by [IrCl 2 Cp*] 2 or [RuCl 2 ( p cymene)] 2 yielded Ni/Ir and Ni/Ru complexes 3 5 and 3 6 (Figure 1 15). 27 Monometallic NHC complexes involving the same ligand can be produced, but subsequent metalations were unsuccessful due to the reactivity o f the NHC moiety. Formation of the Pd/Ag heterometallic complex 3 7 occurred after in situ formation of the Ag NHC and transmetalation with Pd (Figure 1 16) 31 The phenanthroline bound silver could also

PAGE 34

34 then be transmetalated by Cu to form c omplex 3 8 a catalyst for tandem c lick/Sonagashira reactions. Figure 1 15 Synthesis of heterometallic complexes 35 and 36 27 Figure 1 16 Synthesis of heterometallic complexes 37 and 38 31 Another example of exploit at ion of a transmetalation step as a means of controlling reactivity at one site in a multisite ligand involves a ligand produced from metal directed macrocy c lization to form a monometallic Pb precursor (Figure 1 17) 60 Addition of Na 2 [PdCl 4 ] to this precursor results in transmeta lation, and subsequently a variety of metal perchlorates, M(ClO 4 ) 2 can be utilized towards the production of Pd/M heterometallic complexes.

PAGE 35

35 Figure 1 17 S elective addition by transmetal ation. 60 Steric repulsion coordination number and chelation effects Any differences, however slight, between sites in heteroditopic ligands may lead to some measure of preferential metal bi nding to one site over the other. When no clear hard/soft or reactivity differences exist between the two sites, the nature of the ancillary ligand ( s ) and the number and orientation of available coordination sites for the metals of intere st become increas ingly important B ulky ancillary ligands for example, can hinder formation of the unwanted homobimetallic species. Chen and coworkers found this to be the case when following an alternative route towards producing their all N bound Pt/Cu complexes T he y found that C H activation processes catalyzed by their original monometallic Pt complex 32 were slowed by the strongly binding dimethylsulfide ligand 56 They were able to produce an analogue 39 containing no Pt bound SMe 2 by a new route involvin g i nitial deprotonation of their pyrazolate based ligand by KO t Bu and

PAGE 36

36 subsequent treatment with the same Pt(SMe 2 ) 2 (Ph) 2 starting material (Figure 1 18) They propose that the undesired gener ation of homobimetallic species is hindered by the added steric b ulk of the extra phenyl ligand The targeted heterobimetallic Pt/Cu complex 40 was also produced by further treatment with CuI. Figure 1 18 Alternate route towards production of Pt/Cu comple xes bridged by pyrazolate ligands. 56 Heteroditopic ligands with sites of differing coordination number also offer opportunities for selective production of monometallic complexes containing an available site for subsequent metal addition [Ir 2 (C^N ) 4 Cl 2 ] complexes (where C^N is a derivative of 2 phenylpyridine) are found to bind selectively at bipyridine ( bpy ) or phenanthroline ( phen ) sites in ligands which also contain a dipicolylamine (dpa) site (Figure 1 19 ) 61 62 T he stability of the bidentate ancillary C^N ligands leave s only two coordination sites available on the metal leading to preferentia l binding at the bidentate bpy or phen over the tridentate dpa Alternate site selectivity is observed for ZnCl 2 and Zn(NO 3 ) 2 which react exclusively at the dpa site of related ligands L1 and L2 (Figure 1 20) which also contain one or two bpy sites. 63 66 Th is binding selectivity was found to remain consistent for a variety of L1 derivatives which were then used as Zn 2+ sensors with large dynamic

PAGE 37

37 ranges. Similar ligands with substitution of the dpa substituent(s) at the 4 (and 4') positions were also found to bind Zn (ClO 4 ) 2 as well as Cu (ClO 4 ) 2 at their dpa sites followed by subsequent addition of the same metals at their bpy site as monitored by UV visible spectroscopy. 67 68 The nature of the preference for the dpa site may arise from its enhanced chelate effect wh en compared to bidentate bpy. The amine N which should be more nucleophilic than the pyridine alternatives, may also play a role in encouraging selectivity. Figure 1 19 Selectively prepare d monometallic Ir complexes bearing free dpa ligands for subsequent coordination 61 62 Figure 1 20 Ligands L1 and L2. 63 66 It is evident that ligands with linked bpy and dpa moieties exhibit the type of metal site selectivity which make them potential candidates as platfor ms for heterometallic synthesis. However, up to this point, this avenue has not been pursued and the major application of the site selectivity observed in and the resulting

PAGE 38

38 monometallic comp lexes obtained from such ligands has been in the arena of sensors. As mononuclear complexes of polypyridyl based ligands such as bpy and dpa have been long studied as catalysts for a variety of processes, we aim to evaluate the bpy dpa heteroditopic ligan ds as platforms for the synthesis of heterometallic complexes which may display metal metal cooperativity in catalytic processes. W e have chosen L1 and L2 as model systems for th is study as they are one of the simplest ligands which can be devised to cont ain both the bpy and the dpa moieties In this work, we have probed the reactivity of these ligands with Zn 2+ Rh + Pd 2+ Pt 2+ Co 2+ and Cu 2+ sources, resulting in selective preparation of several well characterized heterometallic complexes.

PAGE 39

39 CHAPTER 2 SYNTHESIS OF Rh/Zn, Rh/Pd, and Rh/Pt COMPLEXES OF L1 AND L2 WITH NMR CHARACTERIZATION METHODS Ligands L1 and L2 and Their Models Ligands L1 and L 2 (Figure 1 20 ) were synthesized as previously reported by substitution of dpa onto appropriate bromomethyl bi pyridine or biphenyl precursors. 48 63 69 As expected the two ligands always showed essentially the same reactivity with any major difference in reaction workups being the result of the lower solubility of L2 and its complexes. 70 The higher solubility of the L1 complexes makes them more a ttractive for future applications as heterobimetallic complexes for use in homogeneous catalysis, but utilization of L2 allows for more facile determination of binding site preferences. Because L2 has a 2:1 ratio of dpa:bpy sites, we can often gather info rmation about the binding site simply by considering the quantity of metal reagent taken up by the ligand in the reaction. NMR techniques, ESI MS a nalysis, elemental analysis, IR, and EPR were used to determine the binding site preferences of various meta ls. These preferences were also probed by comparison of complexes of L1 and L2 with those of the model ligands L 1 L2' bpy0, and L2'' (Figure 2 1 ). Figure 2 1. Model ligands of L1 and L2. Reproduced in part with per mission from Goforth, S.K.; Walroth, R.C.; McElwee White, L. Inorg. Chem. 2013 52 5692 5701. Copyright 2013 American Chemical Society.

PAGE 40

40 Binding Site Determination by NMR Reac tion of L1 and L2 with Zn 2+ Pd 2+ and Pt 2+ sources afforded complexes 41 49 in which metal was bound exclusively at the dpa site (Figure 2 2 ) In contrast, Rh + complexes of L1 and L2 were found to exhibit metal binding only at the bpy site leading to prod uction of complexes 50 51 (Figure 2 3 ) T hese diamagnetic products were characterized primarily through 1 H NMR with assistance from ESI MS and elemental analysis Additionally, gHMBCAD NMR was employed to identify the carbon shifts and establish the conn ectivity along the li gand backbone in each complex. Figure 2 2 Zn, Pt and Pd complexes 44 4 9 Figure 2 3 Rh complexes of L1 and L2.

PAGE 41

41 In all cases, the equivalents of metal reage nt employed matched the number of its preferred binding sites available in the ligand. The resulting proton shifts of L1 and L2 complexes were similar, providing evidence for a consistent binding site preference. Additionally, the symmetry of L2, as dete rmined by considering the aromatic region of the 1 H NMR spectra, did not change upon reaction with 1 equiv of Rh + or with 2 equiv of Zn 2+ Pd 2+ or Pt 2+ If after addition of one equiv of metal reagent the symmetry of the L2 complex is retained, then the m etal preferentially binds at the bpy site. If two equiv can be used to produce a symmetric product, then binding is occurring exclusively at the dpa site. Zn Complexes Complex 41 was synthesized by the method of Zhu. 63 Alt hough an X ray crystal structure of L1 with Zn 2+ bound at the dpa site has been reported, 63 comparison of the NMR spectrum of 41 with that of L1 provides evidence that 41 is also the dominant species in solution (Figure 2 4 ). Specifically, the peaks corresponding to the dpa site (A1 A4) are significantly shifted while the peaks correspondi ng to the bpy site (B1 B3, B1' B3') retain essentially the s ame chemical shifts after metal ation. These labels will be used consistently throughout this text for identifying the particular carbons and hydrogens of L1 and L2 complexes and correspond to the system shown in Figure 2 5 Reaction of two equiv of ZnCl 2 with L2 resulted in the formation of a product that was insoluble in all common organic solvents. Therefore, Zn(OAc) 2 and Zn(NO 3 ) 2 were employed to obtain the soluble Zn/L2 complexes 4 2 and 4 3 w hich were characterized by 1 H NMR. In both the case of the previously known complex 4 3 65 and the new complex 42 two equiv of Zn reagent were reacted with ligand and the products were

PAGE 42

42 characterized without purification. No loss of ligand symmetry was observed in the products. Figure 2 4 1 H NMR comparison of dpa, bpy1, L1 and 41 Figure 2 5 Labeling system used throughout this chapter for protons and carbons of L1 and L2 complexes. In complexes containing a COD ligand, the vinyl and methylene at oms bear the additional labels D1 and D2, respectively.

PAGE 43

4 3 The 1 H NMR peaks associated with the dpa methylene groups display a range of splitting patterns between 41 42 and 43 (Figure 2 6 ). In the Zn(NO 3 ) 2 L2 complex 43 the C1 dpa methylene peaks are split into two distinct diastereotopic doublets ( J = 16) while the other extreme is observed in the case of the ZnCl 2 L1 complex 41 in which only a singlet is observed. The Zn(OAc) 2 L2 complex 42 lies between these two extremes, displaying a very broad doublet Figure 2 6. Methylene region of the 1 H NMR spectra of 41 42 and 43 These varying splitting patterns indicate a range of conformational flexibility around the dpa methylene site arising from the changing lability of Zn 2+ The trend can be explai ned as a counterion effect. As the counterion becomes more strongly coordinating from NO 3 to OAc to Cl the Zn 2+ becomes more electron rich and therefore more labile. In all cases the proton chemical shift of the methylene linker between the dpa and b ipyridine sites is around 3.90 ppm. Diastereotopic methylene

PAGE 44

44 protons, as observed in 43 have b een previously reported for dpa complexes 45 46 48 64 65 T his splitting pattern, which is also fo und in the 1 H NMR spectra of the Pd and Pt complexes of L1 and L2, is confirmation of metal binding at the dpa site. Pd and Pt Complexes Reactions of Na 2 [PtCl 4 ] with one equiv of L1 or 0.5 equiv of L2 in DMSO afforded complexes 44 and 45 In the case of 4 5 the crude chloride salt precipitated directly from the reaction mixture after 24 hours. Addition of aqueous KPF 6 to a concentrated DMSO solution of [ 45 ]Cl 2 or the 44 reaction mixture resulted in formation of the pure PF 6 salts of the complexes. The r eplacement of Na 2 [PtCl 4 ] with Pt(COD)Cl 2 in the presence of Ag(PF 6 ) or Ag(NO 3 ) 2 resulted in a mixture of unidentified products, but in the absence of a Ag reagent, no reaction occurred. In contrast, Pd complexes 46 and 47 were readily obtained by reaction of Pd(COD)Cl 2 with one equiv of L1 or 0.5 equiv of L2 in methanol or THF. Each reaction was allowed to proceed at room temperature overnight resulting in the formation of the product as the chloride salt. In the case of the THF reactions, the products pr ecipitated out of the reaction mixture and could be purified by washing the solid in THF to remove remaining ligand starting material as well as COD. In all cases, further purification was possible by converting the products to their PF 6 salts by treatin g their concentrated solutions with excess aqueous KPF 6 (sat.). For all Pt and Pd complexes 44 4 7 metal binding at the dpa site was confirmed by the diastereotopic methylene protons ( J = 16 Hz) in the 1 H NMR spectrum. As further proof of this binding pref erence by Pt and Pd, the ligand model L2', in which the bipyridine of L2 is replaced with a biphenyl group, was subjected to the same reaction conditions as its L2 counterpart. In the resulting products, 48 and 49 the chemical

PAGE 45

45 shifts associated with the dpa pyridines were identical to those for 45 and 47 respectively. The ESI mass spectrometry data for 45 47 and 49 confirmed the presence of ions containing two Pd or two Pt bound to the ligand. There was no evidence of ions containing three bound metal s in the ESI mass spectrometry data of 45 and 47 consistent with a lack of binding at the bpy site. As further evidence of this fact, mixtures 46 /[Pd 2 (L1)Cl 3 ]Cl ( 52 ) and 47 /[Pd 3 (L2)Cl 4 ]Cl 2 ( 53 ) were produced under various alternative reaction conditions and revealed clear spectroscopic distinctions between mono and dipalladated L1 complexes and between di and tripalladated L2 complexes (Figure s 2 7 and 2 8 ) Specifically, all the 1 H NMR aromatic peaks of the the dipalladated L1 product and the tripalla dated L2 product were observed to have chemical shifts downfield of those of their more monopalladated L1 and dipalladated L2 counterparts. Figure 2 7. Homobimetallic and homotrimetallic complexes 52 and 53 Rh Complexe s Rhodium complexes of L1 and L2, 5 0 and 5 1 were obtained by reaction of the ligands with 0.5 equiv of [Rh(COD)Cl] 2 in either THF or EtOH. Unfortunately, the products were mixed with small amounts of starting material and sometimes trace amounts of unide ntified material. The reaction did not progress any further after 20 minutes, and extending the reaction time to overnight led to decomposition when THF

PAGE 46

46 was the solvent. Although pure 5 0 and 5 1 could not be obtained by recrystallizations or chromatograph y, it was possible to determine the binding site by 1 H NMR spectroscopy. In contrast to what was observed for 41 the dpa peaks in the spectrum of 5 0 remain in place while the bpy peaks are significantly shifted (Figure 2 9 ). In fact, they shift in a man ner identical to that of the bpy peaks in the analogous reaction of bpy0 with [Rh(COD)Cl] 2 to obtain 54 (Figure 2 10 ). Analogous shifts are observed in the spectrum of the L2 complex, 5 1 Both 5 0 and 5 1 were also characterized by ESI TOF mass spectrometr y, and their 1 H and 13 C NMR peaks were fully assigned via gHMBCAD NMR Figure 2 8 Comparison of the aromatic region of the 1 H NMR spectra of complex 47 and mixtures 46 / 52 and 47 / 53 For the mixtures, only A1 A4 peaks for the complexes 52 and 53 are la beled.

PAGE 47

47 Figure 2 9 1 H NMR comparison of L1 and 5 0 Figure 2 10 1 H NMR comparison of bpy0 and 54

PAGE 48

48 Ru Complexes S everal Ru sources including RuCl 3 [RuCl 2 (CO) 2 ] n Ru 2 (OAc) 4 Cl, RuCl 3 (SMe) 2 Ru 3 (CO) 12 and cis [Ru(Cl) 2 (dmso) 4 ] were employed in reactions with L1, L2, dpa, and complex 50 and no us able products were produced (Table 2 1) In some cases, no reaction was observed. In others, only brown insoluble material was obtained and/or the products contained paramagnetic Ru 3+ making them difficult to characterize by NMR. Table 2 1. Attempts to bind Ru to dpa, L1, and Rh bound L1 complex 50 Entry Ligand Ru Source Solvent Temp. Result 1 L1 RuCl 3 THF 66 C no reaction 2 dpa RuCl 3 THF 66 C no reaction 3 L1 RuCl 3 EtOH 79 C no reaction 4 50 RuCl 3 EtOH 79 C unidentifiable product 5 50 [RuCl 2 (CO) 2 ] n THF RT unidentifiable product 6 50 Ru 2 (OAc) 4 Cl EtOH RT insoluble brown powder 7 50 RuCl 3 (SMe) 2 EtOH RT unidentifiable product 8 dpa RuCl 3 (SMe) 2 THF RT unidentifiable product 9 dpa RuCl 3 (SMe) 2 CH 2 Cl 2 RT unidentifiable product 10 dpa RuCl 3 (SMe) 2 neat RT unidentifiable product 11 dpa Ru 3 (CO) 12 THF RT insoluble brown powder 12 50 Ru 3 (CO) 12 THF RT insoluble brown powder 13 L1 Ru 3 (CO) 12 EtOH 66 C insoluble brown powder 14 dpa cis [Ru(Cl) 2 (dmso) 4 ] EtOH RT low conversion 15 L2 cis [Ru(Cl) 2 (dmso) 4 ] EtOH RT insoluble brown powder Heterometallic Rh/Zn, Rh/Pd, and Rh/Pt Complexes With the binding preferences of Zn 2+ Pd 2+ Pt 2+ and Rh + determined, it was reasonable to assume that the metals would display the same selectivity whether or not the ligands were already bound to another metal. If that were the case, it would then be possible to produce Rh/Zn, Rh/Pd, and Rh/Pt complexes without scrambling of metals between binding sites (Figure 2 1 1 ).

PAGE 49

49 Figure 2 1 1 Heterometallic complexes 55 60 Prep aration of the Rh/Zn L1 complex 55 went to completion upon reaction of 0.5 equiv of [Rh(COD)Cl] 2 with 41 in EtOH or THF, and no further purification was re quired as confirmed by elemental analysis and NMR spectroscopy (Figure 2 1 2 ) This result is in contrast to that of performing the same rea ction with L1 instead of the Zn bound complex 41 in which a portion of the L1 starting material always remained unr eacted. Reaction of 0.5 equiv of [Rh(COD)Cl] 2 with 43 achieves similar results though the complex 56 is only sparingly soluble in CH 3 OH and could not be purified. Complex 56 and its L1 analogue 57 can also be obtained by reaction of Zn(NO 3 ) 2 with the Rh complexes 5 0 or 5 1 This ability to alter the order of the meta lation steps and still produce the same product is confirmation that the metals retain their original binding site preferences even in the presence of the other metal. At room temperature, t he proton NMR spectra of both 56 and 57 in CD 3 OD show the diastereotopic dpa methylene protons as the expected pair of mutually coupled doublets. The dpa methylenes of 55 appear as two broad singlets at 4.20 and 4.58 ppm in CD 3 OD and are present as a very flat and broad peak stretching from approximately 3.50 to 4.75 ppm in

PAGE 50

50 the baseline in CDCl 3 At 45 C in CDCl 3 however, the dpa methylene groups are present as two doublets at 4.01 and 4.65 ppm. Figure 2 1 2 Aromatic region of the 1 H NMR spectrum o f complex 55 with that of complex 41 for comparison. Rh/Pd complexes of L1 and L2, 58 and 59 respectively, can be prepared either by addition of [Rh(COD)Cl] 2 to the Pd complexes 46 or 47 or by addition of Pd(COD)Cl 2 to the Rh complexes 5 0 or 5 1 (Figures 2 1 3 and 2 1 4 ). Though the same major product is formed in either case, addition of Pd to Rh complexes 5 0 or 5 1 redissolved in THF does not result in full conversion. Complete conversion to product occurs when either the [Rh(COD)Cl] 2 is added to the Pd com plexes 46 or 4 7 or when the entire reaction is done as a one pot synthesis in EtOH with Rh addition first.

PAGE 51

51 Figure 2 1 3 Complementary routes for the synthesis of 58 Figure 2 1 4 Com plementary routes for the synthesis of 59 Similar reactions to produce Rh/Pt complexes were made difficult by the limited solubility of the available Pt starting materials Na 2 [PtCl 4 ], [ 44 ]PF 6 [ 45 ](PF 6 ) 2 and

PAGE 52

52 [ 45 ]Cl 2 In particular, [ 45 ](PF 6 ) 2 was not so luble in THF, ethanol, methanol, water, or DMSO; and both Na 2 [PtCl 4 ], and [ 44 ]PF 6 were only soluble in DMSO. DMSO was not regarded as a good option since the Rh/Pd complex 59 had quickly decomposed in DMSO, presumably because DMSO is known to readily disp lace COD on Rh + 71 Therefore, only the complex [ 45 ]Cl 2 which is sparingly soluble in methanol, was employed. Reaction of this complex with [Rh(COD)Cl] 2 at room temperature for 5.5 h resulted in the formation of 60 The best method of isolating the heteromet allic complexes was by precipitation using diethyl ether. Attempts to isolate these complexes as salts involving alternative counterions (PF 6 BF 4 B(C 6 H 5 ) 4 B(C 6 F 5 ) 4 ) were generally unsuccessful. Products which did not involve Cl as the counterion were typically very poorly soluble thus limiting their utility as well as the means of their characterization. gHMBCAD NMR Studies Most isolated diamagnetic complexes were analyzed by gHMBCAD NMR 72 74 using a 500 mHz INOVA instrument. This very sensitive technique was necessary for the identification of the 13 C NMR shifts for many of the complexes described in this chapter as even their saturated solutions were fai rly dilute The chemical shifts of A1, A2, A3, and A4 were always identifiable by consideration of their 1 H NMR splitting patterns (Table 2 2 ). The one bond C H couplings were often visible as two signals along the axis of the carbon chemical shift cente red about the axis of the corresponding hydrogen shift. The remaining signals in the gHMBCAD spectra are attributed to the two and three bond C H couplings and could be used along with consideration of one bond couplings and 1 H splitting patterns to follo w the backbone of the ligand and assign all 1 H and 13 C chemical shifts (Tables 2 3 through 2 8 ).

PAGE 53

53 Table 2 2. General splitting patterns for L1 and L2 compounds Property A1 A2 A3 A4 B1 & B1' B2 & B2' B3 & B3' Splitting Pattern ddd td d ddd d d dd J ( Hz) 5.0 1.8 0.8 8.0 1.8 8.0 1.2 5.0 7.5 2.0 8.2 8.2 2.0 As an example the assignment of the 1 H and 13 C NMR chemical shifts for the Rh/Zn complex 55 will be discussed (Figure 2 15). In the 1 H NMR spectrum a signal at 9.25 in is readily identified as A1 due to its dominant J value of 5.3 Hz T he smaller splittings with J values of approximately 1.8 Hz and 0.8 Hz are not resolved for this particular complex In the gHMBCAD spectrum, t he one bond C H coupling for A1 is represented by the two signals alon g the 149.7 ppm 13 C NMR axis at around 9.05 and 9. 2 5 ppm along the 1 H NMR axis (Figure 2 1 6 ). The two bond C H coupling for the A1 proton to the A4 carbon is visible as a crosspeak at the intersection of 9.25 on the 1 H NMR axis and 123.9 on the 13 C NMR ax is Along the same line at 9.25 on the 1 H NMR axis, the three bond C H couplings for this proton to the carbons at A2 and A5 are observed at 140.3 and 155.6 along the 13 C NMR axis. T he two and three bond C H couplings can then be used to follow the entir e ligand backbone for complete assignment of both the proton and carbon NMR shifts. Figure 2 15. Assigned 1 H and 13 C NMR shifts of Rh/Zn complex 55

PAGE 54

54 Figure 2 16. Aryl region of the gHMBCAD spectrum of Rh/Zn comple x 55

PAGE 55

55 Table 2 3 Chemical shift assignments for ligands L1, L2, and L2 Entry Ligand Nucleus Solvent A1 A2 A3 A4 A5 B1 B2 B3 B4 1 a L1 13 C CDCl 3 148.9 136.4 122.8 122.0 159.1 149.5 120.3 137.3 134.2 2 a 1 H CDCl 3 8.53 7.66 7.56 7.15 8.69 8.29 7.83 3 b 1 H CD 3 OD 8.44 7.81 7.67 7.27 8.60 8.18 7.95 4 b 1 H DMSO d 6 8.51 7.80 7.60 7.27 8.66 8.31 7.94 5 a L2 13 C CDCl 3 149.1 136.6 123.1 122.1 159.3 149.7 120.6 137.5 134.7 6 a 1 H CDCl 3 8.53 7.67 7.55 7.15 8.70 8.31 7.84 7 b 1 H CD 3 OD 8.44 7.80 7.6 7 7.27 8.61 8.19 7.95 8 b 1 H DMSO d 6 8.51 7.79 7.59 7.26 8.67 8.33 7.94 9 b L2' 1 H CDCl 3 8.53 7.68 7.62 7.15 7.53 7.47 10 b 1 H DMSO d 6 8.50 7.80 7.61 7.26 7.63 7.48 a Assignments based on gHMBC AD data with consideration of chemical sh ifts and associated 1 H NMR splitting patterns. b Assignments based on chemical shifts and splitting patterns along with comparison to conclusions from related gHMBC AD data. Table 2 4 Chemical shift assignments for ligands L1, L2, and L2. Entry Ligand Nuc leus Solvent B5 B1' B2' B3' B4' B5' C1 C2 C3 1 a L1 13 C CDCl 3 155.2 149.5 120.3 137.3 133.1 153.3 60.0 56.0 19.0 2 a 1 H CDCl 3 8.49 8.24 7.62 3.85 3.76 2.39 3 b 1 H CD 3 OD 8.46 8.15 7.75 3.85 3.79 2.40 4 b 1 H DMSO d 6 8.51 8.26 7.74 3.75 3 .72 2.35 5 a L2 13 C CDCl 3 155.1 60.1 55.8 6 a 1 H CDCl 3 3.85 3.76 7 b 1 H CD 3 OD 3.84 3.78 8 b 1 H DMSO d 6 3.77 3.74 9 b L2' 1 H CDCl 3 3.84 3.73 10 b 1 H DMSO d 6 3.74 3.67 a As signments based on gHMBC AD data with consideration of chemical shifts and associated 1 H NMR splitting patterns. b Assignments based on chemical shifts and splitting patterns along with comparison to conclusions from related gHMBC AD data.

PAGE 56

56 Table 2 5 Chemica l shift assignments for Zn, Pd, and Pt complexes of L1, L2, and L2' Entry Complex Anion Nuc. Solvent A1 A2 A3 A4 A5 B1 B2 B3 B4 1 a 41 (L1, Zn) Cl 13 C CDCl 3 150.5 140.2 123.7 124.8 153.4 150.7 120.6 139.6 127.4 2 a Cl 1 H CDCl 3 9.35 7.90 7.35 7.50 8. 40 8.30 7.64 3 a,c 42 (L2, Zn) OAc 13 C CD 3 OD 148.6 140.6 124.2 124.6 154.8 151.1 120.7 140.0 128.8 4 a,c OAc 1 H CD 3 OD 8.80 8.05 7.55 7.60 8.55 8.35 7.90 5 b 43 (L2, Zn) NO 3 1 H CD 3 OD 7.60 7.06 6.59 6.60 7.43 7.31 6.76 6 a 46 (L1, Pd) Cl 13 C C D 3 OD 150.4 141.0 123.1 124.3 164.6 152.2 120.0 140.8 128.0 7 a Cl 1 H CD 3 OD 8.52 7.96 7.58 7.32 9.10 8.01 8.47 8 b Cl 1 H CDCl 3 8.67 7.81 7.47 7.27 9.25 8.07 8.51 9 b PF 6 1 H CD 3 OD 8.42 8.06 7.65 7.45 9.05 8.05 8.36 10 a 47 (L2, Pd) Cl 13 C CD 3 OD 150.5 141.1 123.2 124.4 164.6 152.4 120.5 141.0 128.9 11 a Cl 1 H CD 3 OD 8.58 8.02 7.60 7.41 9.08 7.97 8.44 12 b Cl 1 H DMSO d 6 8.43 8.07 7.66 7.47 9.06 7.92 8.40 13 b PF 6 1 H DMSO d 6 8.38 8.02 7.60 7.41 8.99 7.87 8.33 14 b 53 (L2, Pd) Cl 1 H CD 3 OD 8.61 8.18 7.72 7.51 9.35 8.28 8.90 15 a 49 (L2', Pd) Cl 13 C CD 3 OD 150.3 140.8 123.0 124.1 164.8 132.8 126.9 131.4 16 a Cl 1 H CD 3 OD 8.55 8.02 7.55 7.43 7.95 7.20 17 a 44 (L1, Pt) PF 6 13 C DMSO d 6 149.5 141.4 124.1 125.4 165.9 15 3.3 119.3 141.6 127.7 18 a PF 6 1 H DMSO d 6 8.65 8.10 7.68 7.47 8.98 8.00 7.73 19 a 45 (L2, Pt) Cl 13 C DMSO d 6 149.5 141.3 124.1 125.4 165.9 153.4 120.0 141.8 128.7 20 a Cl 1 H DMSO d 6 8.64 8.12 7.70 7.50 8.99 7.87 8.35 21 b Cl 1 H CD 3 OD 8.80 8. 05 7.61 7.42 9.02 7.91 8.40 22 b 48 (L2', Pt) Cl 1 H DMSO d 6 8.57 8.05 7.60 7.45 7.79 7.06 a Assignments based on gHMBC AD data with consideration of chemical shifts and associated 1 H NMR splitting patterns. b Assignments based on chemical shifts a nd splitting patterns along with comparison to conclusions from related gHMBC AD data. c Spectra also include peaks corresponding to the OAc groups at 179.3 and 21.8 ppm in the 13 C NMR and 2.01 ppm in the 1 H NMR.

PAGE 57

57 Table 2 6 Chemical shift assignments for Zn, Pd, and Pt complexes of L1, L2, and L2' Entry Complex Anion Nuc. Solvent B5 B1' B2' B3' B4' B5' C1 C2 C3 1 a 41 (L1, Zn) Cl 13 C CDCl 3 156.3 149.8 120.6 134.2 137.7 152.4 55.5 53.0 18.5 2 a Cl 1 H CDCl 3 8.50 8.20 7.66 4.10 3.90 2.40 3 a,c 42 (L2, Zn) OAc 13 C CD 3 OD 55.4 53.2 4 a,c OAc 1 H CD 3 OD 4.20 3.85 5 b 43 (L2, Zn) NO 3 1 H CD 3 OD 2.87 3.27 2.71 6 a 46 (L1, Pd) Cl 13 C CD 3 OD 156.4 149.3 120.9 134.8 137.8 151.9 67.4 63.7 16.8 7 a Cl 1 H CD 3 OD 8.45 8.08 7.75 4.75 5.57 4.43 2.40 8 b Cl 1 H CDCl 3 8.45 8.11 7.59 5.28 5.84 4.87 2.39 9 b PF 6 1 H CD 3 OD 8.49 8.13 7.74 4.70 5.58 4.39 2.35 10 a 47 (L2, Pd) Cl 13 C CD 3 OD 155.3 67.4 63.6 11 a Cl 1 H CD 3 OD 4.72 5.52 4.41 12 b Cl 1 H DMSO d 6 4.74 5.62 4.39 13 b PF 6 1 H DMSO d 6 4.66 5.54 4.33 14 b 53 (L2, Pd) Cl 1 H CD 3 OD 4.99 5.42 4.45 15 a 49 (L2', Pd) Cl 13 C CD 3 OD 141.1 67.5 66.4 16 a Cl 1 H CD 3 OD 4.66, 5.49 4.30 17 a 44 (L1, Pt) PF 6 13 C DMSO d 6 156.0 150.1 120.8 134.6 138.1 152.3 68.4 64.3 18.3 18 a PF 6 1 H DMSO d 6 8.48 8.12 8.30 4.98, 5.42 4.45 2.40 19 a 45 (L2, Pt) Cl 13 C DMSO d 6 154.8 68.5 64.3 20 a Cl 1 H DMSO d 6 5.02, 5.45 4.50 21 b Cl 1 H CD 3 OD 4.99, 5.36 4.48 22 b 48 (L2', Pt) Cl 1 H DMSO d 6 4.98, 5.47 4.35 a Assignments based on gHMBC AD data with consideration of chemical shifts and associated 1 H NMR splitting patt erns b Assignments based on chemical shifts and splitting patterns along with comparison to conclusions from related gHMBC AD data. c Spectra also include peaks corresponding to the OAc groups at 179.3 and 21.8 ppm in the 13 C NMR and 2.01 ppm in the 1 H NMR

PAGE 58

58 Table 2 7 Chemical shift assignments for Rh, Rh/Zn, Rh/Pd, and Rh/Pt complexes of bpy0, L1, L2, and L2' Entry Complex Nuc. Solv. A1 A2 A3 A4 A5 B1 B2 B3 B4 B5 1 a 5 4 (bpy0, Rh) 13 C CDCl 3 147.3 125.0 142.3 137.4 154.5 2 a 1 H CDCl 3 7.51 9.05 8.08 3 a 50 (L1, Rh) 13 C CDCl 3 149.1 136.7 123.4 122.4 158.1 148.0 124.6 141.6 138.5 155.4 4 a 1 H CDCl 3 8.47 7.63 7.39 7.13 7.85 8.96 8.14 5 b 1 H CD 3 OD 8.48 7.79 7.58 7.29 7.89 8.26 8.13 6 a 51 (L2, Rh) 13 C CDCl 3 149.1 136. 7 123.4 122.4 158.1 148.0 125.2 141.7 138.6 155.4 7 a 1 H CDCl 3 8.46 7.63 7.39 7.12 7.83 9.16 8.16 8 b 1 H CD 3 OD 8.47 7.80 7.58 7.29 7.89 8.24 8.14 9 a 5 5 (L1, RhZn) 13 C CDCl 3 149.7 140.3 124.7 123.9 155.6 151.6 123.4 144.7 134.7 154.8 10 a 1 H CDCl 3 9.25 7.69 7.45 7.34 8.24 8.37 8.74 11 a 57 (L1, RhZn) 13 C CD 3 OD 148.5 141.2 124.5 124.8 155.2 150.9 122.0 143.3 133.4 156.2 12 a 1 H CD 3 OD 8.89 8.01 7.50 7.66 7.99 8.18 8.26 13 a 5 6 (L2, RhZn) 13 C CD 3 OD 152.2 145.7 129.0 129.1 159.0 154. 8 126.9 147.5 137.3 159.7 14 a 1 H CD 3 OD 8.77 8.12 7.61 7.72 7.90 8.31 8.27 1 5 a 5 8 (L1, RhPd) 13 C CD 3 OD 150.3 141.2 123.5 124.6 164.6 152.5 122.0 143.9 132.2 156.6 16 a 1 H CD 3 OD 8.64 8.04 7.64 7.43 8.83 8.08 8.43 17 a 59 (L2, RhPd) 13 C CD 3 OD 150.5 141.4 123.5 124.7 164.4 152.8 123.0 144.1 133.3 155.2 18 a 1 H CD 3 OD 8.62 8.07 7.67 7.48 8.84 8.04 8.46 19 a 60 (L2, RhPt) 13 C CD 3 OD 149.2 141.0 123.6 125.0 165.2 153.7 122.9 144.2 132.5 154.8 20 a 1 H CD 3 OD 8.81 8.08 7.65 7.48 8.77 7.98 8.4 0 a Assignments based on gHMBC AD data with consideration of chemical shifts and associated 1 H NMR splitting patterns. b Assignments based on chemical shifts and splitting patterns along with comparison to conclusions from related gHMBC AD data.

PAGE 59

59 T able 2 8 Chemical shift assignments for Rh, Rh/Zn, Rh/Pd, and Rh/Pt complexes of bpy0, L1, L2, and L2' Entry Complex Nuc. Solv. B1' B2' B3' B4' B5' C1 C2 C3 D1 D2 1 a 5 4 (bpy0, Rh) 13 C CDCl 3 18.9 84.3 30.5 2 a 1 H CDCl 3 2.42 4.49 2.65, 2.14 3 a 50 (L1, Rh) 13 C CDCl 3 147.2 125.1 142.1 137.4 154.1 59.8 54.2 18.6 84.2 30.3 4 a 1 H CDCl 3 7.45 9.02 8.00 3.75 3.68 2.34 4.48 2.09, 2.57 5 b 1 H CD 3 OD 7.76 8.23 8.03 3.88 3.84 2.44 4.66 2.24, 2.63 6 a 51 (L2, Rh) 13 C CDCl 3 59.8 54.3 84.3 30.4 7 a 1 H CDCl 3 3.75 3.67 4.51 2.12, 2.57 8 b 1 H CD 3 OD 3.88 3.84 4.64 2.26, 2.64 9 a 5 5 (L1, RhZn) 13 C CDCl 3 147.6 124.1 141.7 137.7 153.7 57.0 55.9 18.7 85.3 30.3 10 a 1 H CDCl 3 7.40 8.42 7.93 None 4.3 6 2. 35 4. 49 2. 09 2. 57 11 a 5 7 (L1, RhZn) 13 C CD 3 OD 149.0 122.7 141.3 139.0 153.1 56.7 55.7 17.0 85.4 29.8 12 a 1 H CD 3 OD 7.77 8.25 8.06 4.18 2.45 4.86 2.24, 2.66 13 a 5 6 (L2, RhZn) 13 C CD 3 OD 60.2 58.4 33.9 14 a 1 H CD 3 OD 4.15 4.68 2.26, 2.68 15 a 5 8 (L1, RhPd) 13 C CD 3 OD 149.4 123.0 141.4 139.5 152.5 67.2 62.4 17.0 86.0 30.0 16 a 1 H CD 3 OD 7.79 8.20 8.05 4.80 5.56 4.50 2.45 4.79 2.28, 2.71 17 a 59 (L2, RhPd) 13 C CD 3 OD 67.4 62.4 87.2 30.0 18 a 1 H CD 3 OD 4.83 5.57 4.53 5.06 2.34, 2.79 19 a 60 (L2, RhPt) 13 C CD 3 OD 68.4 63.2 87.1 30.2 20 a 1 H CD 3 OD 5.06 5.37 4.55 4.99 2.37, 2.75 a Assignments based on gHMBC AD data with consideration of chemical shifts and associated 1 H NMR split ting patterns. b Assignments based on chemical shifts and splitting patterns along with comparison to conclusions from related gHMBC AD data.

PAGE 60

60 Hydrogen/Deuterium Exchange in Rh/Pd and Rh/Pt Complexes When dissolved in CD 3 OD at room temperature, complexes 58 60 undergo hydrogen/deuterium exchange for one of the two hydrogens at their dpa methylene sites (Figure 2 1 7 ) For each complex, the downfield dpa methylene doublet at approximately 5.5 ppm is observed initially and then disappears over time while its u pfield partner at around 4.6 ppm morphs into a singlet (Figure 2 1 8 ). The remaining proton shifts are unaffected, indicating that the only change occurring is the replacement of hydrogen by deuterium. Figure 2 1 7 H/ D exchange reaction observed for complex 60 in CD 3 OD. Analogous chemistry is observed for complexes 58 and 59 Exchange was also observed when employing CH 3 OD as the NMR solvent with suppression of the CH 3 signal. This confirms incorporation of the acidi c proton of the methanol and rules out mechanisms involving hydride elimination from coordinated methoxide. The exchange was found to be reversible when the deuterated solvent was removed and replaced with CH 3 OH or CH 3 CH 2 OH. Variable temperature NMR st udies of complex 58 established that the exchange does not occur at 20 C. The selectivity for exchange of only one of the dpa hydrogens observed in the Rh/Pd and Rh/Pt complexes indicates that the Pd and Pt moieties remain firmly bound to the dpa site w hile in solution.

PAGE 61

61 Figure 2 1 8 1 H NMR spectra of 60 in CD 3 OD at 25C as one of the dpa methylene protons is exchanged with deuterium. Similar behavior was observed in spectra for 58 and 59 Control Experiments with Monometallic, Homometallic, and Rh /Zn Complexes This rapid hydrogen/deuterium exchange is not observed in the monometallic L1 or homobimetallic L2 counterparts of these complexes. The dpa bound Pt and Pd complexes 44 4 7 all retain their dpa methylene peaks even after remaining in CD 3 OD ov er several days. The Rh/Zn complex 55 also retains both diastereotopic dpa methyl ene peaks in the proton NMR at 40 C after dissolution in CD 3 OD for over a week at room temperature. These results are consistent with both metals being necessary for the e xchange process. To further probe the participation of the two metals in the exchange process, monometallic complexes Zn(dpa)Cl 2 ( 61 ) [Pd(dpa)Cl]Cl ( 62 ) and [Pt(dpa)Cl]Cl ( 63 ) were synthesized by the same methods as their L1 and L2 analogues and then an alyzed by 1 H NMR in CD 3 OD. One equivalent of

PAGE 62

62 the bpy0 bound Rh complex 54 was added to each solution. As expected, no H/D exchange occurred for the Zn complex 61 Rapid H/D exchange was observed at the dpa methylene site of the Pd complex 62 but there was no selectivity between the methylene hydrogens. H/D exchange was also observed with the Pt complex 63 in the presence of 54 but the selectivity could not be determined due to coincidence of one of the diasterotopic proton signals with the methanol so lvent peak. These experiments demonstrate that H/D exchange of the methylene protons of a (dpa)Pd or (dpa)Pt moiety occurs in the presence of the (bpy)Rh species 54 The two metals need not be bound into the same complex for H/D exchange to occur. Howev er, the selectivity between the diastereotopic methylene protons for H/D exchange in the heterometallic complexes 58 60 suggests that the geometric constraints and preorganization in these complexes can control their reactivity. Kinetic Studies Kinetic st udies of the H/D exchange in Rh/Pt complex 60 were carried out by recording NMR spectra of two methanolic solutions of 60 with concentrations of 2.4 mM and 5.2 mM (Figure 2 1 9 ). Good linear fits were found for the plots of ln[ 60 ] t versus time. As the deu terium source methanol is the solvent, these data indicate pseudo first order reaction kinetics for the exchange. Setting the intercepts at ln[ 60 ] 0 the rate constants found for both the 2.4 mM and 5.2 mM solutions were both 5.2 x 10 4 s 1 with R 2 values of 0.99. The first order dependence on concentration of the heterometallic complex is consistent with an intramolecular process as opposed to a reaction involving the Rh portion of one molecule and the Pt portion of another, which would be expected to be second order in the heterometallic complex. Similar first order dependence was observed for analogous experiments with Rh/Pd L2 complex 59 though R 2 values were

PAGE 63

63 significantly lower. No zero first or second order fits could be obtained from experime nts performed with the Rh/Pd L1 complex 58 This finding may be indicative that the intermolecular exchange process may be providing more competition when steric restraints are lowered as is the case for L1 which only has one pendant Pd bound dpa arm. Figure 2 1 9 Plots of ln[ 60 ] t versus time for two solutions with initial concentrations of 5.2 mM and 2.4 mM. To explore the source for the geometric constraints which lead to selectivity, the Pt L2 complex 4 5 was also mixed with Rh complex 54 in a 1:1 ra tio in CD 3 OD at 25 C. No observable H/D exchange occurred within the first 2.5 hours. This finding supports an intramolecular process for exchange in the heterometallic Rh/Pt L2 complex 60 as that process occurs well within this time range. After 11 ho urs the same downfield proton which exchanged in the heterometallic cases was also fully deuterated in the Pt L2 case. Since no such selectivity is observed for the Pd dpa complex 62 the basis for

PAGE 64

64 the selectivity in this Pt L2 case is probably the steric constraints added by the bpy moiety. Mechanistic Considerations and Implications All of the results regarding these H/D exchange experi ments are summarized in Table 2 9 Simple molecular modeling using Spartan 75 in dicates a facile approach from the Rh center to the dpa methylene proton which is furthest from the bpy moiety ( Figures 2 20 and 2 21 ). There is no evident approach for the dpa methylene proton closest to the bpy ring which would involve reasonable overla p with empty orbitals on the Rh center. Observation of H/D exchange is consistent with either C H activation to produce a Rh hydride or formation of an agostic intermediate followed by H/D exchange with the acidic deuterium of CD 3 OD and release of the C D bond from the metal. 76 77 The contribution of the Pt or Pd to the reaction is likely to be elec tronic in nature especially considering the lack of H/D exchange reactivity in the Rh/Zn complex. Table 2 9 Summary of H/D e xchange e xperiments Entry Compound/Mixture Time Solvent Result 1 58 (Rh/Pd L1) 2 h CD 3 OD selective exchange 2 59 (Rh/Pd L2) 2 h CD 3 OD selective exchange 3 60 (Rh/Pt L2) 2 h CD 3 OD selective exchange 4 47 (Pd L2) 2 weeks CD 3 OD no exchange 5 5 5 (Rh/Zn L1) 1 week CD 3 OD no exchange 6 62 (Pd dpa) + 5 4 (Rh bpy) 10 min CD 3 OD non selective exchange 7 6 3 (P t dpa)+ 5 4 (Rh bpy) 10 min CD 3 OD non selective exchange 8 6 1 ( Zn dpa)+ 5 4 (Rh bpy) 1 day CD 3 OD no exchange 9 45 (P t L2 )+ 5 4 (Rh bpy) 11 h CD 3 OD selective exchange 10 58 (Rh/Pd L1) 2 h CH 3 OD selective exchange 11 60 (Rh/Pt L2) 2 h CH 3 OD selective exchange

PAGE 65

65 The presence of an intramo lecular H/D exchange process in these complex es has implications for the possibility of cooperative activity between the two metal sites in future catalytic applications. A ny substrate bound to a metal at the dpa site would be the same number of bonds awa y from a bpy bound Rh center as the exchanged dpa methylene hydrogen. Additionally, a similar orientation of such a substrate in relation to the Rh could be achieved by an opposing conformation of the molecu le. Simple Spartan models of such a conformer o f an M/Rh heterobim etallic L1 complex indicate that the shortest possible distance between metal centers in these complexes is ca. 5.6 If no control is placed over the rotation of the C N bond between the dpa amine and the bpy dpa linking methylene gro up, then this distance becomes ca. 8.0 Both of these are within the range of metal metal distances found in cooperative heterometallic systems described in Chapter 1. Conclusions The metal binding selectivity of the dpa and bpy sites of ligands L1 and L2 was probed using NMR spectroscopy, ESI MS, elemental analysis, and comparison with model complexes. Rh was found to bind selectively at the bipyridine site, while Zn, Pd, and Pt were found to bind at the dpa site. These selectivities were exploited in the synthesis of heterometallic Rh/Zn, Rh/Pt, and Rh/Pd complexes 55 60 Selective hydrogen/deuterium exchange was observed when the heterometallic Rh/Pd and Rh/Pt complexes 58 60 were dissolved in CD 3 OD. For the Rh/Pt complex, the exchange was found to obey first order kinetics suggesting an intramolecular process. This is evidence of cooperativity between the two metal sites as control experiments involving monometallic and homometallic analogues as well as the Rh/Zn complex 5 3 indicate that both the Rh and Pt or Pd metals are required for the H/D exchange.

PAGE 66

66 Figure 2 20 Two 180 views of a Spartan model of binding between Rh center and dpa methylene proton in 58 Figure 2 21 ChemDraw representations of possible interac t ions between the Rh center and dpa methylene protons of 58 A) B ased on Spartan model pictured in Figure 2 20 B) Also based on Spartan model pictured in Figure 2 20 but viewed from a different angle C) B ased on an alternative Spar tan model (not pictured) of a second possible interaction between Rh and H a

PAGE 67

67 CHAPTER 3 SYNTHESIS AND CHARACTERIZATION OF PARAMAGNETIC Co 2+ AND Cu 2+ COMPLEXES OF L1 AND L2 INCLUDING Rh/Cu, Pd/Cu, AND Pt/Cu HETEROMETALLIC COMPLEXES In order to further expl ore the versatility of L1 and L2 as platforms for heterometallic complexes involving additional metal combinations, we have extended our studies to include Cu and Co. The inclusion of first row metals in new catalysts is of interest as these metals are ch eaper, more readily available, and often more reactive than precious metals such as Rh, Pd, and Pt. In addition, combination of one of these first row metals with a precious metal in a heterometallic complex may lead to interesting activity. In particul ar, Pd/Cu and Pt/Cu heterobimetallic complexes have been targeted in a number of synthetic studies. 31 54 56 58 The motivation behind the Pd/Cu synthetic studies arises from the diverse chemistry of the individual Pd and Cu metals towards small molecule substrates 55 58 as well as the cooperativity they often display when working together as separate entities. The latter is particularly noted for the Wacker process and for certain Sonagashira coupling reactions. 54 It has been proposed that new reactivities, particularly in the area of oxidation chemistry, might be achieved when Pd and Cu are covalently linked and heterometallic Pd/Cu complexes have already found som e successes in early catalytic studies. 31 54 Similar r eactivities could be explored for the corresponding Pt/Cu heterometallic complexes. Such complexes may also be useful as model systems for intermediates in the reactions of their Pd/Cu analogues, given the ability of Pt to form stronger bonds than Pd. 55 Material in this chapter is derived from the following reference: Goforth, S.K.; Walroth, R.C.; Angerhofer, A.; McElwee White, L. manuscript in preparation

PAGE 68

68 Cu and Co Binding Site Preferences for L1 and L2 For the Rh + Pt 2+ Pd 2+ and Zn 2+ comple xes, NMR was the primary means of binding site determination. Unfortunately, preparation of diamagnetic Co 3+ complexes was problematic as Co 3+ reagents are inert and also are often not soluble in the same solvents as L1 and L2. Though NMR spectra of Co 2+ complexes are known 78 79 they do not contain detailed splitting patterns such as those which were useful in assigning the diamagnetic systems. When diamagnetic Cu + complexes of L1 and L2 were prepared, they were found to easily oxidize so that even NMR samples prepared under inert atmosphere displayed broadened signals due to the presence of Cu 2+ We thus needed to employ other techniques in order to determine the binding site preferences of paramagnetic Cu 2+ and Co 2+ moieties. Based o n the UV visible studies of Shinkai and Takeuchi in which Cu(ClO 4 ) 2 was found to bind preferentially to the dpa sites of similar ligands, it was likely that other Cu 2+ sources would have the same binding preferences in L1 and L2. 67 68 However, the binding preferences of Co 2+ in similar ligands ha d not been explored, and UV visible studies analogous t o those of Shinkai and Takeuchi employing Co 2+ sources were inconclusive. Initial indication that CoCl 2 preferentially binds at the dpa site was gleaned from the physical properties of the CoCl 2 complexes of the ligands L1 and L2 and their ligand models. In contrast to the turquoise precipitates which resulted from reactions of CoCl 2 with bpy0, all reactions of CoCl 2 with L1, L2, L1', and L2' produced purple products. Additionally, the turquoise bpy0 complex was insoluble in all common organic solvents, while in every case but that of L2, the purple complexes were very soluble in CH 3 CN and CH 3 OH.

PAGE 69

69 IR Studies of Co and Cu Complexes Though this similarity of physical properties is supporting evidence for dpa selectivity by CoCl 2 more conclusive proof was fo und through a series of IR studies. When compared, the spectra of L1 and L2 undergo qualitatively similar changes when the ratio of CoCl 2 added to L1 versus CoCl 2 added to L2 is 1:2 (Figure 3 1 ). Since there is a 1:2 ratio of dpa sites in L1 to dpa sites in L2, these results suggest that binding is occurring at the dpa site. If binding occurred at the bpy site, there should be more similarities between the spectra of L1 and L2 each with 1 equivalent of CoCl 2 added. The same series of CoCl 2 additions was performed with L2' as the ligand, and the resulting spectral changes matched very well with those of the L2 study. Similar studies performed with Cu(OTf) 2 and Cu(NO 3 ) 2 gave analogous results (Table s 3 1 and 3 2 ) The region between 1440 cm 1 and 1620 cm 1 maintained a consistent profile for the final products resulting from reactions with each of these three reagents. This region of the IR spectra, associated with vibrations involving the pyridine rings, 80 82 was therefore identified as a marker for determining whether or not binding occurred at the dpa site (Figure 3 2 ). Specifically, each spectrum contained a major peak between 1606 cm 1 and 1613 cm 1 a much s maller peak between 1571 cm 1 and 1576 cm 1 and two broad peaks of approximately equal or lesser intensity than the first between 1478 cm 1 and 1487 cm 1 and between 1444 cm 1 and 1451 cm 1 The same IR profile was observed in this region for the product s of reactions of the ligands with Pd(COD)Cl 2 and Zn(NO 3 ) 2 which are both independently known to bind at the dpa site based on NMR studies.

PAGE 70

70 Table 3 1. Vibrational frequencies between 1420 cm 1 and 1620 cm 1 of l igands and of reaction mixture s of ligands with sub stoichiometric amounts of various metal sources. Entry Ligand Metal Source Ratio (L:M) IR Stretches a (neat, cm 1 ) 1 L1 1590 (s), 1568 (m), 1553 (m), 1472 (m), 1460 (s), 1438 (s), 1428 (s) 2 L2 1590 (s), 1568 (s), 1554 (m), 1473 (s), 145 8 (s), 1434 (s) 3 1589 (s), 1569 (s), 1519 (w), 1486 (s), 1473 (s), 1432 (s) 4 1586 (s), 1568 (m), 1494 (m), 1473 (s), 1429 (s) 5 1548 (s), 1496 (m), 1458 (m), 1449 (m) 6 L1 Cu(CF 3 SO 3 ) 2 1:0.5 1607 (m), 1590 (ms), 1570 (m), 1476 (s), 1435 (s) 7 L2 Cu(CF 3 SO 3 ) 2 1:1 1608 (s), 1591 (s), 1571 (m), 1556 (w), 1475 (s), 1434 (s) 8 Cu(CF 3 SO 3 ) 2 1:0.5 1609 (s), 1572 (m), 1521 (w), 1487 (s), 1448 (s) 9 Cu(CF 3 SO 3 ) 2 1:1 1611 (s), 1598 (m), 1573 (m), 1498 (m), 1482 (m), 1449 (s) 10 L1 Cu(NO 3 ) 2 1:0.5 1607 (s), 1594 (s), 1571 (m), 1556 (w), 1477 (s), 1435 (s) 11 L2 Cu(NO 3 ) 2 1:1 1609 (s), 1596 (s), 1572 (m), 1479 (s), 1447 (s), 1435 (s) 12 L1 CoCl 2 1:0.5 1604 (m), 1591 (s), 1570 (m), 1554 (w), 1500 (w), 1474 (s), 1435 (s) 13 L2 CoCl 2 1:1 1605 (s), 1591 (s), 1570 (m), 1556 (w), 1474 (s), 1435 (s) 14 CoCl 2 1:1 1607 (s), 1589 (s), 1570 (m), 1497 (m), 1475 (m), 1433 (s) a In reality all IR bands were of either medium or weak intensity. However, in order to better describe the differences in intensity relative strong, medium, and weak classifications were applied. The strongest peak between 1400 cm 1 and 1620 cm 1 was defined as having intensity 3 and the intensities of all other peaks were scaled appro priately. Peaks were then label ed as weak with intensities between 0 and 1, medium with intensities between 1 and 2, and strong with intensities between 2 and 3.

PAGE 71

71 Table 3 2 Vibrational frequencies between 1420 cm 1 and 1620 cm 1 of products complete ly metal ated in either the dpa or bpy site(s) in the given ligand. Entry Ligand Metal Source Rat io (L:M) IR Stretches a (neat, cm 1 ) 1 L1 Cu(CF 3 SO 3 ) 2 1:1 1609 (s) 1576 (wm) 1482 (s) 1450 (m) 2 L2 Cu(CF 3 SO 3 ) 2 1:2 1611 (s) 1576 (w) 1482 (m) 1451 (m) 3 Cu(CF 3 SO 3 ) 2 1:1 1613 (s) 1576 (w) 1487 (s) 1450 (s) 4 Cu(CF 3 SO 3 ) 2 1:2 1613 (s) 1575 (w) 1498 (w) 1486 (m) 1450 (s) 5 Cu(CF 3 SO 3 ) 2 1:1 1604 (m) 1584 (m) 1495 (ms) 1477 (s) 1456 (s) 6 L1 Cu(NO 3 ) 2 1:1 1609 (s) 1574 (m) 1504 (w) 1481 (s) 1448 (s) 7 L2 Cu(NO 3 ) 2 1:2 1611 (s) 1575 (w) 1481 (s) 1450 (s) 8 L1 CoCl 2 1:1 1606 (s) 1571 (m) 147 8 (s) 1444 (s) 9 L2 CoCl 2 1:2 1607 (s) 1572 (m) 1479 (s) 1446 (s) 10 CoCl 2 1:1 1607 (s) 1573 (w) 1485 (s) 1444 (s), 1435 (s) 11 CoCl 2 1:2 1606 (s) 1572 (m) 1498 (w) 1480 (m) 1444 (s) 12 CoCl 2 1:1 b 1600 (m) 1582 (w) 1493 (m) 1471 (s) 1452 (s) 13 L1 Zn(NO 3 ) 2 1:1 1608 (s) 1575 (m) 1483 (s) 1447 (s) 14 L2 Zn(NO 3 ) 2 1:2 1610 (s) 1575 (m) 1482 (s) 1446 (s) 15 L1 Pd(COD)Cl 2 1:1 1609 (s) 1572 (w) 1558 (w) 1474 (s) 1448 (s) 16 L2 Pd(COD)Cl 2 1:2 1610 (s) 1572 (w) 1556 (w) 1474 (s) 1448 (s) 1 7 Pd(COD)Cl 2 1:2 1610 (s) 1571 (w) 1498 (w) 1482 (m) 1447 (s) 18 L1 Na 2 [PtCl 4 ] 1:1 1615 (m), 1599 (m) 1572 (w) 1556 (w) 1488 (m), 1482 (m), 1466 (s) 1445 (s) 19 L2 Na 2 [PtCl 4 ] 1:2 1612 (s), 1600 (m) 1578 (w) 1558 (w) 1485 (m), 1469 (m) 1446 (s) 20 bp y0 [Rh(COD)Cl] 2 1:1 1604 (w) 1576 (w) 1505 (w) 1473 (w) a See note a in Table 3 1. b IR stretches recorded for the compound [(L2'') 2 Co( Cl) 2 CoCl 2 ] ( 64 ) which crystallized out of a mixture containing a ratio of 1:2 L2'':CoCl 2 The c rystal structure can b e found in Figure 3 3

PAGE 72

72 Figure 3 1 IR study of the addition of CoCl 2 to L1, L2, and L2'. The IR profiles of L2'' complexes of Co and Cu, which must involve bpy binding, are distinctly different from those of their dpa bound counterparts. Instead of the strong peak associated with C=C stretching between 1609 cm 1 and 1613 cm 1 found in the Cu dpa bound complexes, a much weaker peak is observed at 1604 cm 1 Similarly, the L2'' complex of Co which was identified as [(L2'') 2 Co( Cl) 2 CoCl 2 ] ( 64 ) by X r ay crystallography (Figure 3 3 Table 3 3, Table 3 4 ), contains the weaker peak at 1600 cm 1 in place of the peak between 1606 cm 1 and 1607 cm 1 observed in the dpa bound Co complexes. These findings are consistent with other reported asymmetric C=C stre tches for dpa and bpy complexes. 80 83 Additionally, the L2'' complexes display three

PAGE 73

73 medium or strong peaks in the 1450 cm 1 to 1500 cm 1 region as opposed to th e two generally observed for the dpa bound complexes. Figure 3 2 Expansion of the 1 35 0 cm 1 to 1 7 00 cm 1 region of the IR spectra of L1, L2, L1', L2', and L2'' bound to PdCl, CoCl 2 or Cu(OTf) 2 In all spectra involving ligands L1, L2, L1', or L2' the equiv of metal match the number of dpa sites. The spectra involving L2'' correspond to entries 5 and 12 of Table 3 2. EPR Studies of Cu Complexes EPR spectra were obtained for various mixtures of ligands with Cu(OTf) 2 in CH 3 OH and in 50:50 DMSO/H 2 O at 20 K. Because the spectra of mixtures of L1, L2, and L2' with ratios of Cu 2+ equal to the number of available dpa sites were very broad, EPR parameters were obtained for mixtures involving half those ratios. For the ligand models bpy and dpa, Cu(OTf) 2 was added in a 1:1 ratio. For most samples, these glass EPR spectra were of an axial type (Table 3 5 ) as expected based on literature results for dpa and bpy bound Cu 2+ complexes. 84 85 There was no distinction between the g values obtained for the complexes in either solvent. However, in DMSO/H 2 O, EPR parameters for the parallel region of dpa and dpa bound L2' complexes are significantly

PAGE 74

74 different from those for bpy complexes. As parameters for L1 and L2 most closely match those of the dpa bound controls, dpa binding selectivity is supported. This comparison can be easily observed with visual inspection of the spectra for L1 and L2 which correspond with that of L2' but not with that of bpy0 (Figure 3 4 A D ). Though the g || values obtained for all of the complexes in CH 3 OH were essentially the same, the A || coupling constants showed a similar trend to that obs erved in the DMSO/H 2 O cases. Figure 3 3. Thermal ellipsoids diagram of complex 6 4 Thermal ellipsoids are plotted at 4 0% probability.

PAGE 75

75 Table 3 3 Crystal data and structure refinement for complex 64 Empirical formula C 80 H 76 Cl 4 Co 2 N 8 C 2 H 3 N 1 Formula w eight 1450.20 T (K) 100(2) () 0.71073 Crystal system Monoclinic Space group P2 1 /n a () 16.6789(19) b () 25.461(3) c () 17.4733(19) (deg) 90 (deg) 104.906(2) (deg) 90 Volume ( 3 ) 7170.7(14) Z 4 calcd (Mg/m 3 ) 1.351 (mm 1 ) 0.667 F 000 3024 Crystal size (mm 3 ) 0.32 x 0.05 x 0.03 range (deg) 1.45 to 20.32 Index ranges Reflections collected 67880 Independent reflections 6985 [R(int) = 0.0515] Completeness to = 27.50 99.6 % Absorptions correction Empirical Max./ min. trans mission 0.9791/ 0.8151 Refinement method Full matrix least squares on F 2 Data/restraints/ parameters 6985/0/ 875 GOF on F 2 1.039 Final R1 a 0.0260 Final wR2 b 0.0561 [5728] R1 (all data) 0.0392 wR2 (all data) 0.0617 Largest diff. peak/ hole (e. 3 ) 0.219 / 0.274 a R1 = (||F o | |F c ||) / |F o |; b wR2 = [ [w(F o 2 F c 2 ) 2 ] / [ w( F o 2 ) 2 ]] 1/2 ; S = [ [w(F o 2 F c 2 ) 2 ] / (n p)] 1/2 ; w= 1/[ 2 (F o 2 )+(m*p) 2 +n*p], p = [max(F o 2 ,0)+ 2* F c 2 ]/3, m & n are constants.

PAGE 76

76 Figure 3 4 Glass EPR spectra of Cu, Pd/Cu, and Pt/Cu complexes in 50:5 0 DMSO/H 2 O at 20 K. Solid and dotted lines are to guide the eye. A) L1 + Cu(OTf) 2 B) L2 + Cu(OTf) 2 C) L2 + Cu(OTf) 2 D) bpy0 + Cu(OTf) 2 E) Complex 69 F) Complex 67 G) Complex 68 H) Complex 69 I) Complex 70 J) Complex 71

PAGE 77

77 Table 3 4 Se lected bond lengths () and bond angles () for complex 6 4 Co1 N2 2.098(2) N3 Co1 Cl1 95.60(7) Co1 N3 2.102(2) N1 Co1 Cl1 89.19(6) Co1 N1 2.124(2) N4 Co1 Cl1 172.32(7) Co1 N4 2.124(2) Cl2 Co1 Cl1 87.42(3) Co1 Cl2 2.4981(8) Cl4 Co2 Cl3 119.38(4) Co1 Cl1 2.5088(8) Cl4 Co2 Cl2 115.52(3) Co2 Cl4 2.2406(9) Cl3 Co2 Cl2 106.33(3) Co2 Cl3 2.2417(9) Cl4 Co2 Cl1 106.80(3) Co2 Cl2 2.3213(9) Cl3 Co2 Cl1 110.03(3) Co2 Cl1 2.3237(8) Cl2 Co2 Cl1 96.29(3) N2 Co1 N3 170.19(9) Co2 Cl1 Co1 87.80(3) N2 Co 1 N1 77.74(10) Co2 Cl2 Co1 88.12(3) N3 Co1 N1 94.23(9) C3 N1 C1 118.7(2) N2 Co1 N4 97.27(9) C3 N1 Co1 126.32(19) N3 Co1 N4 77.62(9) C1 N1 Co1 114.97(19) N1 Co1 N4 94.87(8) C23 N2 C21 119.0(2) N2 Co1 Cl2 95.34(7) C23 N2 Co1 125.2(2) N3 Co1 Cl2 92.98(6 ) C21 N2 Co1 115.77(19) N1 Co1 Cl2 172.30(7) C43 N3 C41 118.7(2) N4 Co1 Cl2 89.30(6) C43 N3 Co1 124.53(19) N2 Co1 Cl1 89.95(6) C41 N3 Co1 115.94(18) Table 3 5 EPR data obtained from mixtures of Cu(OTf) 2 and various ligands at 20 K. a Entry Ligands So lvent g || g A || (10 4 cm 1 ) 1 DMSO/H 2 O b 2.42 2.08 130 2 bpy0 DMSO/H 2 O c 2.31 2.07 163 3 dpa DMSO/H 2 O c 2.26 2.05 179 4 L2' DMSO/H 2 O c 2.25 2.07 177 5 L1 DMSO/H 2 O c 2.27 2.08 187 6 L2 DMSO/H 2 O c 2.25 2.06 183 7 CH 3 OH d 2.43 2.09 122 8 bpy0 CH 3 OH e 2.27 2.06 162 9 dpa CH 3 OH e 2.26 2.05 177 10 L2' CH 3 OH e 2.27 2.06 173 11 L1 CH 3 OH e 2.24 2.06 185 12 L2 CH 3 OH e 2.24 2.06 183 a For solutions involving bpy0, dpa, L2', or L2, the ratio of ligand to Cu 2+ was 1:1. For the solutions involving L1, this ratio was 1:1.5. b 50:50 DMSO/H 2 O, 1.44 mM in Cu(OTf) 2 c 50:50 DMSO/H 2 O, 1.44 mM in ligand. d 1.0 mM in Cu(OTf) 2 e 1.0 mM in ligand.

PAGE 78

78 Addition of 2 equiv of Cu(OTf) 2 to L1 in either methanol or 50:50 DMSO/H 2 O results in EPR spectra exhibiting eight lines in the parallel reg ion rather than the four observed for the dpa bound Cu 2+ complexes (Figure 3 5, A B) This doubling of the hyperfine lines is consistent with two Cu 2+ centers separated by a fixed distance. Setting the exchange interaction to 3 x 10 4 MHz, a good fit for the DMSO/H 2 O case could be found with the following EPR parameters : g || = 2.38 g = 2.07 A || = 160 x 10 4 cm 1 and A = 39 x 10 4 cm 1 A signal which is present at half field also gives evidence of an interaction between two Cu 2+ centers (Figure 3 5, C D ) Figure 3 5 EPR spectra for 2:1 mixtures of Cu(OTf) 2 and L1. A) I n 50:50 DMSO/H 2 O. B) I n methanol C) I n 50:50 DMSO/H 2 O at half field D) I n methanol at half field

PAGE 79

79 Rh/Cu Complexes The differing binding selectivities of Rh and Cu for the bpy and dpa sites within L1 and L2 suggest that Rh/Cu complexes of L1 and L2 should be readily accessible by both routes in Figure 3 6 A rust colored product is obtained upon reaction of 1 equiv of Cu(OTf) 2 with Rh L1 complex 50 An identical product wi th a matching IR spectrum can be obtained from reacting 0.5 equiv of [Rh(COD)Cl] 2 with a freshly prepared solution of L1 and Cu(OTf) 2 in a 1:1 ratio (Figure 3 7 ) Very similar IR spectra can also be obtained for the brown products of analogous L2 reaction s involving 1:1:2 ratios of L2 to Rh to Cu using the same Rh and Cu sources. EPR spectra of the complexes in CH 3 OH are also unaffected by order of metal addition and indicate the presence of only one type of Cu 2+ center (Figure 3 8 ). The EPR parameters o btained from these spectra are very similar to those of the bpy and dpa Cu(OTf) 2 complexes with the A || values being more consistent with those of the dpa complexes (Table 3 6 ). EPR of these complexes using 50:50 DMSO/H 2 O was not possible as DMSO is known to readily replace COD on Rh complexes. 71 The composition of the products was confirmed by elemental analysis and the [M OTf] + ion for complex 65 was observed by ESI MS These Rh/Cu heterometallics are more stable than their Rh/Pt, Rh/Pd, and Rh/Zn count erparts. The IR spectra of the complexes remain unchanged after 2 months of storage in a desiccator, and the elemental analysis of the Rh/Cu L2 complex 66 was obtained 75 days after it was synthesized. Table 3 6 EPR data for Rh/Cu complexes in MeOH at 2 0 K. Entry Complex g || g A || (10 4 cm 1 ) 1 65 2.23 2.05 179 2 66 2.23 2.06 179

PAGE 80

80 Figure 3 6 Complementary routes for the synthesis of 65 The synthesis of the Rh/Cu L2 complex 66 is analogous Figure 3 7 IR spectra of the samples obtained from different routes of synthesizing 65 and 66

PAGE 81

81 Figure 3 8 EPR spectra of the samples obtained from different routes of synthesizing 65 and 66 Pd/Cu and Pt/Cu Complexes In 50:50 DMSO/H 2 O, the glass EPR spectra of 1: 1 mixtures of Cu(OTf) 2 with various L1 and L2 complexes of Pd 2+ or Pt 2+ were recorded (Table 3 7 ). In contrast to the results for mixtures of Cu(OTf) 2 with the ligands alone, the resulting EPR parameters match those of the bpy0 case rather than that of L2 (Figure 3 4 C I ). This result is consistent with dpa selective Cu 2+ binding at the bpy site because the dpa site is blocked by the already bound Pd 2+ or Pt 2+ (Figure 3 9 ). Addition of more than one equivalent of Cu(OTf) 2 to these solutions of Pd and Pt complexes of L1 and L2 does not

PAGE 82

82 lead to replacement of the Pd or Pt centers by Cu. Instead, the same 6 7 69 products are observed as mixtures with free Cu(OTf) 2 Despite changes in metal (Pt 2+ or Pd 2+ ), ligand (L1 or L2), and counterion (PF 6 or Cl ), al l of the EPR spectra of complexes 6 7 70 are essentially superimposable. Table 3 7 EPR data obtained for Pd/Cu and Pt/Cu complexes in 50:50 DMSO/H 2 O at 20 K. Entry Ligand First Metal Added Second Metal Added Counterion Product g || g A || (10 4 cm 1 ) 1 L1 Pd Cu Cl 69 2.31 2.07 163 2 L2 Pd Cu Cl 67 2.32 2.07 161 3 L2 Pt Cu Cl 68 2.32 2.07 161 4 L1 Pd Cu PF 6 69 2.31 2.07 163 5 L1 Pt Cu PF 6 70 2.31 2.07 163 6 L1 Cu Pd Cl 71 2.27 2.07 168 Pd/Cu and Pt/Cu L2 complexes 67 and 68 can be easily iso lated and purified by reaction in CH 3 OH as the mint green products precipitate from the reaction mixture. The same products are produced from 1:1.1 and 1:2 mixtures of the Pd or Pt L2 complexes [ 47 ]Cl 2 or [ 45 ]Cl 2 with Cu(OTf) 2 confirming that Cu 2+ does no t exchange with the Pd 2+ The slightly darker mint green L1 product 69 can also be obtained from a 1:1 mixture of the Pd L1 complex [ 46 ]Cl with Cu(OTf) 2 in methanol by precipitation with diethyl ether. When Cu 2+ is first allowed to react with L1 in methan ol and followed by addition of Pd(COD)Cl 2 a grayish teal precipitate begins to form within 5 minutes (Figure 3 10 ). The product 71 which clearly has different physical properties than 69 also has a different EPR spectrum (Figure 3 4 J ) that more close ly corresponds to dpa bound Cu 2+ than bpy bound Cu 2+ The compositions of the isolated Pd/Cu and Pt/Cu complexes 67 69 and 71 were confirmed by elemental analysis. For complex 71 the binding of both Cu and Pd to L1 was confirmed by the presence of [(L1 )CuPdCl 2 ] 2+

PAGE 83

83 [(L1)CuPd(OTf)Cl] 2+ and [(L1)CuPd(OTf)Cl 2 ] + in the mass spectrum though none of these ions contain both of the (L1)Cu(OTf) 2 moieties proposed. Initial attempts to obtain mass spectra containing heterometallic Pd/Cu and Pt/Cu ions of complex es 6 7 6 9 were unsuccessful due to the lability of the Cu moiety. However, when the samples were made at 2 mM concentrations, multiple ions corresponding to complexes 6 7 6 9 with loss of Cl and/or OTf ions were observed. Figure 3 9 Reaction of Pd and Pt complexes with Cu(OTf) 2 Figure 3 10 Synthesis of Pd/Cu complex 71 with bpy bound Pd and dpa bound Cu. Conclusions Heterometallic Rh/Cu, Cu/Pd, and Cu/Pt complexes have been selecti vely prepared through the use of ligands containing linked dipicolylamine (dpa) and bipyridine (bpy) sites. The two sites have different selectivities for metal binding, which allows prefere ntial formation of singly metal ated complexes. IR and EPR method s were

PAGE 84

84 employed for binding site determination of Co 2+ and Cu 2+ which were both found to exhibit dpa selectivity. Based on the previously reported bpy binding selectivity exhibited by Rh + this allowed for the formation of Rh/Cu complexes by either order of metal addition. In contrast, the dpa selective metals Pd 2+ and Pt 2+ can be used to block dpa binding by Cu 2+ to yield Pd/Cu and Pt/Cu complexes with bpy bound Cu 2+ Similarly, initial addition of Cu 2+ to L1 followed by reaction with Pd(COD)Cl 2 leads t o a heterometallic complex containing dpa bound Cu 2+ and bpy bound Pd 2+

PAGE 85

85 CHAPTER 4 ELECTROCHEMICAL STUDIES OF L1 AND L2 COMPLEXES Background on Heterobimetallic Electroc atalysts for Alcohol Oxidation with Application to Direct Alcohol Fuel Cells Direct a lcohol fuel cells (DAFCs) are promising as portable energy sources due to a number of desirable alcohol properties. 86 90 Alcohols are inexpensive and abundant a 1 for methanol and 8.0 1 for ethanol). Also, t hey are liquids and thus are easier to store and distribute as compared to the more commonly used H 2 gas. Finally, alcohol fuel cells can be operate d at low temperatures. The higher mass energy density, biorenewability, and lower toxicity of ethanol make it an even more desirable fuel than methanol. Figure 4 1. Reactions in the two alternative pathways for the complete 6 e oxidation of methanol to CO 2 In heterogeneous systems, the complete oxidation of methanol to CO 2 is a multistep 6 e process involving formaldehyde, CO, and formic acid as intermediates (Figure 4 1). 91 95 When methanol is present in excess, the 2 e oxidation product formaldehyde can undergo a condensation reaction with methanol to form dimethoxymethane. Similarly, the 4 e oxidation product f ormic acid can go on to form

PAGE 86

86 methyl formate. The complete oxidation of ethanol to CO 2 involves analogous intermediates and side products (Figure 4 2) 96 97 but is complicated by the additional carbon carbon bond which needs to be broken. Figure 4 2. Selected reactions along pathways for the oxidation of ethanol to CO 2 Platinum is the traditional anodic metal used in heterogeneous systems for the electrochemical oxidation of methanol. 98 However, the catalysis is hindered by the poisoning of the Pt electrode by CO, which is formed as an intermediate in the complete 6 e oxidation of methanol. Incorporating an ox ophilic metal such as Ru into the electrode along with the Pt has been found to alleviate this problem leading to more effective catalysis with oxidation of methanol at lower potentials and with less CO poisoning. 99 101 It is believed that the two metals are able to work together cooperatively, with the Pt dehydrogenating the alcohol and a Ru oxo species delivering oxygen to CO to form CO 2 102 103 In the case of Pt/Ru anodes, only the metal atoms on the surface are able to take part in the oxidation. In this reg ard, employing bulk Pt/Ru anodes in mass produced fuel cells would not be practical as most of the precious metal atoms would not be in

PAGE 87

87 use. This problem could be solved by instead using a homogenous catalyst system. Because the catalyst would be in the s ame phase as the alcohol, each metal atom would have the potential to be an active site for the oxidation. In the past, McElwee White et al. have studied a range of heterobimetallic complexes in which the two metals are bridged by bidentate phosphines and halogens (Figure 4 3). 13 93 94 97 104 106 Metal combinations employed in these studies include Ru/Pt, Ru/Pd, Fe/Pt, F e/Pd, Fe/Au, Ru/Cu, and Ru/Sn. Figure 4 3. Examples of dppm bridged complexes along with examples of their electrochemical studies. 13 93 97 105 106 The activity of these complexes as catalysts for the electrochemical oxidation of methano l and ethanol was studied through the use of cyclic voltammetry and bulk electrolysis. 13 97 Each of the complexes listed exhibited a significant current increase in the oxidation wave of one of the metals in the cyclic voltammogram up on being treated with either methanol or ethanol as expected for successful catalytic oxidation. Bulk

PAGE 88

88 electrolysis of both methanol and ethanol was then conducted in the presence of catalyst in order to identify and quantify the oxidation products. The p roducts observed in the methanol oxidations were dimethoxymethane and methyl formate, while the ethanol oxidation s generated acetaldehyde, acetic acid, 1,1 diethoxyethane, and ethyl acetate. Complete oxidation to CO 2 was never observed and the turnover num bers were low. The low turnovers can in part be attributed to catalyst degradation which most likely occurs through oxidation of the phosphine ligands. These results suggested the use of new ligand architectures which do not involve the easily oxidized p hosphines. Considerations Involving Metal Selection As previously mentioned, Direct Ethanol Fuel Cells (DEFCs) are more attractive than Direct Methanol Fuel Cells (DMFCs) for a variety of reasons. However, in order to utilize the full mass energy density of ethanol, complete oxidation to CO 2 is necessary and so the carbon carbon bond must be broken. Since acetaldehyde is one of the known intermediates involved in the oxidation of ethanol, one method of breaking the carbon carbon bond could be decarbonyla tion of this aldehyde. It has been long known that homogeneous Rh complexes are able to stoichiometrically and catalytically perform decarbonylations (Figure 4 4 ). 107 109 Towards this end Rh was incorporated into the heterometallic complexes of L1 and L2 along with Pt or Pd which are known to be capable of binding and dehydrogenating alcohols. Ru incorporation into the L1 and L2 complexes was also desirable due to the higher current efficiencies obtained from alcohol oxidations using the dppm bridged heterobimetallic complexes which contained Ru 13 97 However, as described in C hapter 2, the initial exploration of the binding preferences of this metal to ligands L1 and L2 w as unsuccessful.

PAGE 89

89 Concurrently, the inclusion of cheaper, more readily available, and often more reactive first row metals is also of interest. As a starting point, Cu and Co were identified as targets for the same reasons as Pt, Pd, and Rh. Cu complexes, including those involving dpa mo ie ties, have been known to catalyze alcohol oxidations. 110 115 At the same time, Co comple xes have found limited use in th e area of aldehyde decarbonylation chemistry 116 121 Thus these metals also have the potential to be included in heterobimetal lic complexes for electrochemical alcohol oxidation. Figure 4 4. Examples of stoichiometric and catalytic decarbonylation using Rh compounds. 107 109 Cyclic Voltammetry of Complexes of L1 and L2 Selection of a suitable solvent for the electrochemical characterization of the L1 and L2 complexes was complicated by the limited solubility which many of them display. The complexes di sp lay the best solubility in DMSO; however, as discussed in Chapter 2 the Rh complexes decompose in DMSO after initial substitution of the solvent molecules for the COD ligand. During synthesis methanol and ethanol have proven to be the most successful s olvents for sol ubility of the L1 and L2 complexes. While this could

PAGE 90

90 facilitate homogeneous electrochemical oxidation of these alcohols, these are not ideal solvents for the electrochemical characterization process Because methanol and ethanol are the in tended substrates, a different solvent must be employed in order to detect the effect of added alcohol in cyclic voltammograms and to have a reasonable substrate to catalyst ratio for bulk electrolysis. After testing the solubility of the complexes in a r ange of common solvent s for electrochemistry, acetonitrile was chosen as the primary solvent for these studies as most of the complexes were at least partially soluble. Dichloroethane (DCE), which was a primary solvent used for the electrochemistry of the dppm bridged complexes, was also employed for the L1 and L2 complexes that it was able to solubilize. Rh/Zn L1 Complex A 5 mM solution of the Rh/Zn L1 complex 53 displays several redox waves within the solvent window of a 0.1 M solution of tetrabutylammon ium hexafluorophosphate ( TBAH ) electrolyte in CH 3 CN (Figure 4 5 A ) A clear Rh(II/III) couple is observed at 0.8 4 V and is consistent with literature reports for [Rh( bpy )( COD )] ClO 4 complexes 122 as well as with Rh bpy complex 54 (Figure 4 5B) The Rh(I/II) couple can also be det ected at around 1.3 7 V, but it has interference from reduction waves associated with the Zn portion of the molecule as evidenced by comparison with the voltam m ogram of Zn L1 complex 41 (Figure 4 5C) As assigned by comparison with the cyclic voltammogram of L2 (Figure 4 5D), w aves associated with ligand redox include a redox couple at 2.0 3 V and a broad irreversible oxidation wave spanning from 1.9 4 V to the upper edge of the solvent window. Cyclic voltammetry of L1 and its Zn, crude Rh, and Rh/Zn compl exes 41 50 and 53 w as also performed in 0.1 M tetrabutylammonium triflate (TBAT) in dichloroethane (DCE), but the solvent window was only large enough to accommodate

PAGE 91

91 the irreversible ligand oxidation wave s (Figure 4 6 ). The oxidations associated with th e ligand in this alternative solvent are observed to be very complex and diverse across these four voltammograms and begin anywhere from around 0.5 to 2.0 V Figure 4 5. C yclic v oltamm ogram of Rh/Zn complex 55 with those of 54 41 and L2 for compari son. All were performed at 5 mM concentrations in CH 3 CN /TBAH under N 2 atmosphere with potential recorded versus NHE. A) Rh/Zn complex 5 5 B) Rh bpy complex 54 C) Zn L1 complex 41 D ) Ligand L2.

PAGE 92

92 Figure 4 6. Cyclic v oltammetry of L1 and its Zn ( 41 ) crude Rh ( 50 ) ,and Rh/Zn ( 55 ) complexes in DCE/TBAT under N 2 atmosphere with potential recorded versus NHE. Rh/Pd and Rh/Pt Complexes Electrochemical characterization of the Rh/Pd and Rh/Pt complexes is complicated by a few factors including the solubili ty issues already discussed. None of these complexes a re very soluble in any solvents, and the Rh/Pt L2 complex 60 is only really soluble in methanol. Therefore, 5 mM concentrations were not possible and so signals were less pronounced than those in the voltammograms already described. Additionally, comparison of voltammograms of the Rh/Pd and Rh/Pt complexes with those of related Pd and Pt complexes 44 47 and 62 63 is difficult as these display even more limited solubility than their heterobimetallic R h/Pd and Rh/Pt counterparts. Only the Pd dpa complex 62 exhibited significant redox waves as a saturated solution in CH 3 CN/TBAH. The Pd(II/IV) wave occurred at 1.35 V which presents an additional complication as this is in the same re gion as the irrevers ible ligand oxidations. Pt(II/IV) waves are similarly expected to occur around 1.7 V which would also be in the region spanned by the ligand oxidation waves.

PAGE 93

93 C yclic voltamm etry of Rh/Pd L1 complex 58 was first performed in 0.1 M tetrabutylammonium tetraf luoroborate (TBABF 4 ) in DCE (Figure 4 7 ). A broad wave with a maximum at 1.4 V is probably overlapped Pd(II/IV) and ligand oxidation wave s. Addition of ethanol to the system results in an increase in the current of these oxidation s but the increase is s imilar in magnitude to that observed when EtOH is added to the DCE blank alone. Thus, the complex does not show significant activity towards ethanol oxidation. Figure 4 7 Cyclic voltammogram of Rh/Pd L1 complex 58 and the effect of EtOH addition; per formed in DCE/ TBABF 4 under o pen atmosphere with potential recorded versus NHE. Electrochemical characterization of the Rh/Pd complexes 58 (Figure 4 8A) and 59 (Figure 4 8B) was attempted in CH 3 CN/TBAH; however, the complexes decomposed over the course of s uccessive cyclic voltammograms as evidenced by a change of solution color from orange to blackish brown. Limited comparisons may be made between these cyclic voltammograms and those of related compounds 62 (Figure 4 8C), 54 (Figure 4 8D), and L2 (Figure 4 8E). Both voltammograms for 58 and 59 exhibit a very sharp unidentified reduction wave near the reversible ligand couple at 1.78 V for

PAGE 94

94 58 and 1.93 V for 59 A reduction wave at 0.5 1 V observed for the L2 complex 59 is consistent with a Pd(II/I) reduc tion, a Pd(II/0) reduction, or a combination of these two. 123 An analogous reduction wave is observed in the voltammogram of Pd dpa complex 62 For the L1 complex, this wave is observed as a shoulder to the Rh(II/III) couple at 0. 90 V while the Rh(II/III) couple occurs at 1.40 V. The Rh(I/II) and Rh(II/III) couples were not observed in the voltammogram of 59 though very small perturbations in the correct region for these oxidations were observed It is possible that the irreversible reduction wave observed at 1.14 V is simply masking the presence of these couples. If this is the case, and if this peak is not the result of complex decomposition, then it may be a ligand or Pd reduction. The voltammogram of 62 does exhibit an irreversible reduction wave in this region. For the L1 complex, a w eak couple occurs in th is same region at 1.1 8 V The shape of the waves in the ligand oxidation region morphed throughout successive voltammograms of these complexes in CH 3 CN Of particular note, the peak at around 1.5 V in the voltammogram of 58 was initially around 0. 2 mA in intensity, dropped to 0. 1 mA two scans later ( Figure 4 8A), increased back to 0. 2 mA within another 6 scans, and decreased again to 0. 1 mA on the next scan. The broad ligand band of waves at higher potential also morphed in shape and complexity throu g hout these scans. When EtOH was introduced to the system, the peak shape s were even more drastically altered with an additional wave being observed at around 1.2 V (Figure 4 9). A new wave also appeared in this region when EtOH was added to complex 59 Both the oxidation and reduction currents near the edges of the solvent window increase d when EtOH was added to these systems

PAGE 95

95 Figure 4 8. Cyclic voltammograms of Rh/Pd complexes 58 and 59 with those of [Pd(dpa)Cl]Cl, 54 and L2 for comparison. All w ere performed in CH 3 CN/TBAH under N 2 atmosphere with potential recorded versus NHE. A) Saturated solution of Rh/Pd L1 complex 58 B) Saturated solution of Rh/Pd L2 complex 59 C) Saturated solution of Pd dpa complex 62 D) 5 mM solution of Rh bpy compl ex 54 E) 5 mM solution of L2.

PAGE 96

96 Figure 4 9 Cyclic voltammogram of Rh/Pd L1 complex 58 and the effect of EtOH addition; performed in CH 3 CN/ TBA H under N 2 with potential recorded versus NHE. Cyclic voltammetry experiments of the L2 complex 59 were also p erformed in 0.1 M TBAT in methanol with approximately 2 mM of these complexes (Figure 4 10 ) The solvent window is smaller in this case than CH 3 CN solutions. The Pd only complex 47 exhibits a wave at 1.7 V which would be the beginning of the Pd(II/IV) wa ve and/or the ligand oxidation waves In the CV of the Pd/Rh L2 complex 59 the oxidation current in this region is larger tha n that of the Pd only complex. The Rh/Pt complex 60 was not soluble enough in CH 3 CN for a cyclic voltammogram to be attempted in that solvent. The complex is soluble in DMF and two irreversible oxidation waves were observed at 1.34 V and 0.88 V (Figure 4 11). to the system.

PAGE 97

97 Figure 4 10 Cyc lic voltammetry of Rh/Pd L2 complex 59 and Pd L2 complex 47 ; performed in MeOH/ TBABF 4 under open atmosphere with potential recorded versus NHE. Figure 4 11 Cyclic voltammogram of Rh/P t L2 complex 60 and the effect of EtOH addition; performed in DMF/ T BA H under o pen atmosphere with potential recorded versus NHE. Rh/Cu L1 Complex Cyclic voltammograms of the Rh/Cu complex 65 were measured at a 5 mM concentration in CH 3 CN/TBAH (Figure 4 1 2 A ). Assignments were made by comparison with the cyclic voltammogra ms of a 1:2 mixture of L2 and Cu(OTf) 2 (Figure 4 12B), Rh bpy complex 54 ( Figure 4 12C), and ligand L2 (Figure 4 12D). The Rh(I/II) and Rh(II/III)

PAGE 98

98 couples are found at 1.42 V and 0.90 V. Similar waves to those which could not be fully identified in the Rh/Pd complexes were also observed at 1.70 V and 1.15 V. This suggests that the wave in the 1.70 V region is a ligand reduction whose potential is increased upon metal binding. The weak couple at 1.15 V in this complex 65 and in Rh/Pd L1 complex 58 may also be ligand related. All of these waves remained essentially unchanged over the course of 11 scans of varying potential ranges. The Cu related waves which appear at around 0.07 V, however, morph into a variety of shapes with successive scans (Figu re 4 13) In scans in which the intensity of the wave at 0.07 is diminished, t he oxidation wave at 0.34 V and the reduction wave at 0.13 V seem to converge to the familiar shape of a reversible couple at 0.28 V Couples in this general range have been o bserved for other Cu dpa complexes in the literature. 124 125 No increases in current were observed at any of the Cu or Rh related waves upon addition of ethanol to the system. Current i ncreases were observed at the edges of the solvent window, with a particularly large increase in reduction current at the negative potential maximum. The same situations wer e found to occur in successive voltammograms of the proposed (Cu(OTf) 2 ) 2 (L2) complex. Bulk Electrolysis of Heptanal with Rh L1 Complex The crude Rh L1 complex 50 was tested for its activity as an electrochemical catalyst for decarbonylation of aldehydes through bulk electrolysis of 0.3 M hexanal in the presence of 0.01 M catalyst. Pentane was observed as a product by gas chromatography with a turnover number (TON) of 2.2 and a current efficiency of 7.8 % (Figure 4 14 ). Though the TON is poor, the reactio n is catalytic. This demonstrates proof of concept that the Rh portion of the target complexes is able to catalyze the electrochemical decarbonylation of aldehydes.

PAGE 99

99 Figure 4 1 2 Cyclic voltammograms of Rh/Cu complex 65 with additional voltammograms fo r comparison. All were performed at 5 mM concentrations in CH 3 CN/TBAH under N 2 atmosphere with potential recorded versus NHE. A) Rh/Cu L1 complex 65 B) Product of a reaction of L2 with two equivalents of Cu(OTf) 2 C) Rh bpy complex 54 D) L2. Conclus ions The bulk electrolysis data for the catalytic decarbonylation of hexanal by the crude monometallic Rh L1 complex 50 are encouraging for possible ethanol oxidation applications However, n one of the cyclic voltammograms of these complexes give promisin g evidence for their use as catalysts for the electrochemical oxidation of alcohols. As already noted, the electrochemical characterization of these complexes is hindered by their poor solubility, but even those soluble in CH 3 CN exhibit complex electroche mical behavior While the Rh(I/II) and Rh(II/III) couples can usually be readily

PAGE 100

100 identified, oxidation waves of the Cu, Pd, and Pt centers can be difficult to detect and identify For the Rh/Cu L1 complex 65 the changing morphology in the Cu(I/II) wave region of the cyclic voltammograms throughout many cycles suggests that these compounds are reactive under the associated electrochemical conditions. As the potential for the these waves is dependent upon the coordination sphere and geometry of the Cu cen ter, 126 128 the changing morphology is perhaps evidence of decomposition or of ancillary ligand dissociation reactions in solution including substitution by the co ordinating solvent In the case of the Pd and Pt complexes, ligand oxidations occur in the same region as the expected Pd(II/IV) or Pt(II/IV) waves and so elucidation of their location is difficult. The changes in morphology in this region over multiple cycles may also point to changes in the coordination sphere around these metal centers throughout the course of the electrochemical experiments In the cyclic voltammograms of all of these complexes, m ost of the limited increases in oxidation current obse rved upon alcohol addition could be attributed to simple conductivity increases in the solution allowing for better charge transpor t. If some of the difficulties in electrochemical characterization arise from any changes in the geometry of the intended ca talysts during the experiments then different ancillary ligands may serve to improve the performance and allow for more firm definition of the electrochemical characteri stics of these complexes. Additionally, ligand modifications directed at improving so lubility would also be very advantageous As ligands L1 and L2 have been proven to be excellent platforms for the selective synthesis of new heterometallic complexes; these could be reasonable avenue s for future study.

PAGE 101

101 Figure 4 13. Sampling of cyclic voltammograms of Rh/Cu complex 65 in CH 3 CN/TBAH under N 2 atmosphere after various cycles. Cycles 13 and 15 were performed after the addition of 50 L of EtOH. Figure 4 14. Pentane formation observed in the bulk electrolysis of hexanal in the prese nce of 50

PAGE 102

102 CHAPTER 5 ATTEMPTED SYNTHESES INVOLVING AN ALTERNATIVE MULTISITE POLYPYRIDYL LIGAND Bridging Ligand Design and Synthetic Scheme The ligand L 3, which can easily be obtained by a substitution reaction between sodium azide and 2 picolylchloride h ydrochloride followed by subsequent Cu catalyzed click reaction with 2 ethynylpyridine 129 also has the potential to be used for hetero metallic complex synthesis (Figure 5 1) This ligand has been reported to form homobimetallic Cu complexes and t o selectively bind Cu( Cl O 4 ) 2 at its 5 membered ring site (Figure 5 2) 130 As selective preparation of monometallic complexes of this ligand has already been proven, testing their viability as platforms for heterometallic complexes is reasonable. S everal pathways, including those found in Figure 5 3 can be envision ed for the formation of hetero metallic complexes utilizing L 3 Figure 5 1 The multisite ligand L3.. Figure 5 2. Previously reported Cu complexes of L3. 130

PAGE 103

103 Figure 5 3 Scheme for utilization of L3 as a platform for heterometallic complexes. Metal Binding Studies Several experiments were performed involving different combinations of metal salts and solvents ( Table 5 1) A Cu/Co heterobimetallic complex would be attractive as a possible catalyst for the electrochemical oxidation of alcohols due the low cost of the metals involved and the k nown activity of these metals as discussed in Chapter 4. Thus, Co was selected as the second metal for most of the preliminary experiments. Four crystals suitable for X ray diffraction were obtained from the reactions involving these two metals (See Appe ndix A for tables of bond lengths and angles) Fe and Ni were also tested due to their low cost and known catalytic activity, but no crystals suitable for X ray crystallographic analysis were obtained. When a solution of CuCl 2 2 O in MeOH is added dropwi se to a MeOH solution containing two equiv of L 3 a blue solution is obtained. In one trial, the solvent was removed resulting in a pale blue solid which was washed with Et 2 O and then

PAGE 104

104 redissolved in MeOH for vapor diffusion with Et 2 O. This resulted in sq uare blue crystals which upon X ray diffraction were determined to be trans [Cu(Cl) 2 (L 3 ) 2 ] ( 72 ) (Figure 5 4 Table 5 2, Table 5 3 ). In another trial, the solvent was reduced in vacuo and immediately set up for vapor diffusion with Et 2 O. This resulted in teal needlelike crystals of complex 73 with a very similar structure to that of 72 except that the geometry about the Cu center wa s square pyramidal with one of the chloride ions no longer being bound (Figure 5 5 Table 5 2, Table 5 4 ). The apparent labil ity of the Cl ligand to create an empty coordination site in this way is notable as such a site would be necessary for substrate binding to a catalytic Cu center Table 5 1. Metal binding experiments involving L 3 Entry 1 st Metal Source 2 nd Metal Source Reaction Solvent Vapor Diffusion Solvent Crystals 1 CuCl 2 2H 2 O N/A MeOH Et 2 O teal needles, Figure 5 4 2 CuCl 2 2H 2 O N/A MeOH Et 2 O blue cubes, Figure 5 5 3 a CuCl 2 2H 2 O N/A CH 3 CN Et 2 O no 4 CuCl 2 2H 2 O CoCl 2 MeOH hexanes no 5 a CuCl 2 2H 2 O CoCl 2 MeOH Et 2 O mixture, blue and peach 6 CuCl 2 2H 2 O CoCl 2 MeOH Et 2 O blue, Figure 5 6 7 CuCl 2 2H 2 O CoCl 2 CH 3 CN hexanes no 8 CuCl 2 2H 2 O CoCl 2 CH 3 CN Et 2 O no 9 Cu(OAc) 2 H 2 O N/A MeOH Et 2 O no 10 Cu(OAc) 2 H 2 O N/A CH 3 CN Et 2 O no 11 CuCl N/A MeOH Et 2 O no 12 CuCl N/A Me OH hexanes no 13 CoCl 2 N/A MeOH hexanes no 14 CoCl 2 N/A MeOH hexanes peach 15 CoCl 2 6H 2 O N/A MeOH Et 2 O no 16 a CoCl 2 CuCl 2 2H 2 O CH 3 CN Et 2 O no 17 CoCl 2 CuCl 2 2H 2 O MeOH Et 2 O peach, Figure 5 7 18 CoCl 2 6H 2 O Cu(OAc) 2 H 2 O MeOH Et 2 O no 19 CoCl 2 6H 2 O NiCl 2 6H 2 O MeOH Et 2 O orange 20 NiCl 2 6H 2 O N/A MeOH hexanes no 21 NiCl 2 6H 2 O CuCl 2 2H 2 O MeOH Et 2 O green 22 NiCl 2 6H 2 O CoCl 2 MeOH hexanes blue 23 a NiCl 2 6H 2 O CoCl 2 CH 3 CN Et 2 O mixture, blue and lavender 24 FeCl 3 N/A MeOH Et 2 O no 25 FeCl 3 N/A MeOH hexanes no a Reaction performed at reflux rather than room temperature.

PAGE 105

105 Figure 5 4. Thermal ellipsoids diagram of Cu L3 complex 72 Thermal ellipsoids are plotted at 50% probability. Figure 5 5. Thermal ellipsoids diagram of Cu L3 complex 73 Thermal ellipso ids are plotted at 50% probability

PAGE 106

106 Trials involving 1:1:2 ratios of CuCl 2 2 O to CoCl 2 2 O to L 3 also resulted in different crystal structures depending on the order of reagent addition. When CuCl 2 2 O was added to L 3 followed by addition of CoCl 2 2 O, a blue dinuclear Cu complex 74 was observed by vapor diffusion from MeOH with ether (Figure 5 6 ). When instead the CoCl 2 2 O was reacted first followed by CuCl 2 2 O addition, peach crystals of trans [Co(Cl) 2 (L 3 ) 2 ] ( 75 ) were obtained also by vapor dif fusion from MeOH with Et 2 O (Figure 5 7 Table 5 2, Table 5 5 ). A reaction involving an initial 1 h room temperature reaction of CuCl 2 2 O with L3 followed by addition of CoCl 2 and an 8 h reflux resulted in the production of a mixture of both blue and pea ch crystals. While these were not suitable for X ray diffraction, their colors are suggestive of a mixture of monometallic Cu and Co complexes obtained during the room temperature reactions. Figure 5 6. Thermal ellipsoids diagram of Cu L3 complex 74 Thermal ellipsoids are plotted at 50% probability.

PAGE 107

107 Figure 5 7. Thermal ellipsoids diagram of Co L3 complex 75 Thermal ellipsoids are plotted at 50% probability. Conclusion We see in the case of L3 that facile formation of monometallic complexes th rough site selective metal addition does not guarantee the ready synthesis of heterometallic complexes. Though the Cu and Co both preferentially bind to the same site of L 3 they are not inclined towards addition to the second site even when the other met al is already blocking the five membered ring site S ynthesis of the desired Cu/Co heterobimetallic complex using L 3 is therefore challenging. Nonetheless, many possible alterations in reaction conditions still have the potential to induce the formation of heterometallic complexes from these ligands. These include increased ratios of the second metal, variations on the ancillary ligands, and incorporation of different metals.

PAGE 108

108 Table 5 2 Crystal data and structure refinement for L3 complexes 72 73 and 75 a 72 73 75 Empirical formula C 30 H 38 Cl 2 CuN 10 O 4 C 26 H 22 Cl 2 CuN 10 C 26 H 22 Cl 2 CoN 10 Formula weight 737.14 608.98 604.37 T (K) 100(2) 100(2) 100(2) () 0.71073 0.71073 0.71073 Crystal system Monoclinic Triclinic Monoclinic Space group P2(1)/c P 1 P2 (1)/c a () 12.7833(17) 7.6763(10) 10.979(2) b () 7.8316(10) 12.7582(16) 14.842(3) c () 17.296(2) 14.5099(18) 8.2619(18) (deg) 90 93.552(2) 90 (deg) 100.208(8) 91.023(2) 104.051(5) (deg) 90 95.013(2) 90 Volume ( 3 ) 1704.2(4) 1412.5(3) 1306.1 (5) Z 2 2 2 calcd (Mg/m 3 ) 1.437 1.432 1.537 (mm 1 ) 0.849 0.997 0.900 F 000 766 622 618 Crystal size (mm 3 ) 0.20 x 0.17 x 0.15 0.18 x 0.14x 0.10 0.30 x 0.15 x 0.07 range (deg) 1.62 to 27.50 1.41 to 27.50 2.35 to 27.47 Index ranges Reflections collected 21101 18570 1833 Independent reflections 392 3 [R(int) = 0.0844] 6451 [R(int) = 0.0375] 1616 [R(int) = 0.0276] Completeness to = 27.50 100.0 % 99.6 % 54.0 % Absorpt ions correction Numerical Numerical Numerical Max./ min. transmission 0.88 40/ 0.8493 0.9103/ 0.8401 0.9364/ 0.7716 Data/restraints / parameters 3923/0/ 218 6451/ 0 / 353 1616/0/ 178 GOF on F 2 1.018 0.983 0.926 Final R1 0.0362 0.0356 0.0301 Final wR2 0.0880 [305 1] 0.0952 [5102] 0.0544 [1246] R1 (all data) 0.0512 0.0472 0.0444 wR2 (all data) 0.0933 0.0984 0.0584 Largest diff. peak/ hole (e. 3 ) 0.537/ 0.479 0.745/ 0.460 0.281/ 0.206 a In all cases the refinement method was full matrix least squares on F 2

PAGE 109

109 Table 5 3. Selected bond lengths () and bond angles () for complex 72 a Cu1 N2 2.0346(16) N1#1 Cu1 N1 180.000(1) Cu1 N2#1 2.0346(16) N2 Cu1 Cl1 89.04(5) Cu1 N1#1 2.0381(15) N2#1 Cu1 Cl1 90.96(5) Cu1 N1 2.0382(15) N1#1 Cu1 Cl1 87.48(5) Cu1 Cl1 2.7029( 5) N1 Cu1 Cl1 92.52(5) Cu1 Cl1#1 2.7030(5) N2 Cu1 Cl1#1 90.96(5) N2 Cu1 N2#1 180.0 N2#1 Cu1 Cl1#1 89.04(5) N2 Cu1 N1#1 99.36(6) N1#1 Cu1 Cl1#1 92.52(5) N2#1 Cu1 N1#1 80.64(6) N1 Cu1 Cl1#1 87.48(5) N2 Cu1 N1 80.64(6) Cl1 Cu1 Cl1#1 179.999(18) N2#1 Cu 1 N1 99.36(6) a Symmetry transformations us ed to generate equivalent atoms. #1 x+1, y+2, z+2 Table 5 4 Selected bond lengths () and bond angles () for complex 73 Cu1 N10 2.0247(17) N10 Cu1 N4 98.61(7) Cu1 N5 2.0378(18) N5 Cu1 N4 80.36(7) Cu1 N9 2.0435(18) N9 Cu1 N4 167.96(7) Cu1 N4 2.0443(18) N10 Cu1 Cl2 93.98(5) Cu1 Cl2 2.4872(6) N5 Cu1 Cl2 92.24(5) N10 Cu1 N5 173.77(7) N9 Cu1 Cl2 95.20(5) N10 Cu1 N9 80.53(7) N4 Cu1 Cl2 96.84(5) N5 Cu1 N9 99.18(7) Table 5 5 Selected bond lengths () and bond angles () for complex 75 a Co1 N2 2.1009(19) N1#1 Co1 N1 180.0 Co1 N2#1 2.1009(19) N2 Co1 Cl1#1 93.14(9) Co1 N1#1 2.140(2) N2#1 Co1 Cl1#1 86.86(9) Co1 N1 2.140(2) N1#1 Co1 Cl1#1 90.45(8) Co1 Cl1#1 2.4505(10) N1 Co1 Cl1#1 89.55(8) C o1 Cl1 2.4506(10) N2 Co1 Cl1 86.86(9) N2 Co1 N2#1 180.0 N2#1 Co1 Cl1 93.14(9) N2 Co1 N1#1 103.06(8) N1#1 Co1 Cl1 89.55(8) N2#1 Co1 N1#1 76.94(8) N1 Co1 Cl1 90.45(8) N2 Co1 N1 76.94(8) Cl1#1 Co1 Cl1 180.0 N2#1 Co1 N1 103.06(8) a Symmetry transformat ions us ed to generate equivalent atoms. #1 x+1, y+2, z+2

PAGE 110

110 CHAPTER 6 EXPERIMENTAL SECTION General Considerations Unless otherwise noted, all reactions were performed under inert atmosphere using standard Schlenk line and glove box techniques. All anh ydrous solvents were stored over 3 molecular sieves. Dichloromethane, hexane, and toluene were passed through an MBraun MB SP solvent purification system prior to use. Other solvents were distilled from sodium/benzophenone (tetrahydrofuran, diethylethe r), CaH 2 (DMSO), or from magnesium turnings and I 2 (ethanol, methanol). Deuterated NMR solvents were purchased from Cambridge Isotope Laboratories, stored over 3 molecular sieves, and used without further purification. The Pd(COD)Cl 2 and Na 2 [PtCl 4 ] wer e purchased from Strem Chemicals, and all other reagents were obtained from Aldrich and Fisher. All 1 H NMR and 13 C NMR spectra were obtained using either a 300 MHz Mercury, a 300 MHz Gemini, or a 500 MHz INOVA instrument while all gHMBCAD spectra were co llected using the 500 MHz INOVA instrument. High resolution mass spectrometry (HRMS) data were recorded on an electrospray ionization, time of flight (ESI TOF) mass spectrometer. All IR data were collected using a Perkin Elmer Spectrum One FT IR Spectrom eter. CW X band (9.62 GHz) measurements were recorded using a Bruker Elexsys E580 Spectrometer Elemental analyses of [ 4 4 ](PF 6 ), [ 45 ](PF 6 ) 2 [ 47 ](PF 6 ) 2 55 59 65 69 and 71 were performed by Complete Analysis Laboratories in Parsippany, NJ, while that of 54 was performed at the University of Florida. For compounds 58 and 60 repeated attempts to obtain elemental analyses (including duplicate analyses of the same sample by the same laboratory and duplicate

PAGE 111

111 analyses of portions of the same sample by diff erent laboratories) afforded inconsistent results. Synthetic Procedures Syntheses of Ligands T he syntheses of ligands L1, L2, L1', L2', and L2'' and their bromo substituted bipyridine and biphenyl precursors were modified from procedures described by Zhu a nd coworkers for the preparation of L1. 63 The ligand L 3 was obtained by a known substitution reaction between sodium azide and 2 picolylchloride hydrochlo ride followed by subsequent Cu catalyzed click reaction with 2 ethynylpyridine 129 5 bromomethyl 5' methyl 2,2' dipyridyl (bpy1). A 100 mL Schlenk flask containing 5,5' dimethyl 2,2' dipyridyl (bpy0, 0.763 g, 4.14 mmol), NBS (0.739 g, 4.15 mmol), and AIBN (catalytic amount) was charged with 40 mL anhydrous CCl 4 The reaction mixture was refluxed at 77 C for 17 h and then filtered hot to remove the succinimide (0.306 g). The pale yellow filtrate was allowed to sit at room temperature for two days a nd then filtered to yield 0.163 g of the dibrominated product (bpy2) as a white powder. The solvent was removed from the pale yellow filtrate, and the crude product was chromatographed on silica gel using 0 70% EtOAc in DCM to give the monobrominated pr oduct (bpy1) as a white powder (0.578 g, 53%). 1 H NMR (300 MHz, CDCl 3 J = 8.2 Hz, 1H), 8.29 (d, J = 8.2 Hz, 1H), 7.84 (dd, J = 8.3, 1.9 Hz, 1H), 7.64 (dd, J = 8.2, 1.9 Hz, 1H), 4.55 (s, 2H), 2.41 (s, 3H). This co mpound was characterized by comparison to literature data 63 dibromomethyl dipyridyl (bpy2). A 50 mL Schlenk flask was charged with bpy0 (0.381 g, 2.07 mmol), NBS (0.772 g, 4.34 mmol), and a catalytic amount of AIBN. The reagents were suspended in anhydrous CCl 4 (20 ml) and refluxed for 19 h.

PAGE 112

112 The reaction mixture was filtered hot to remove the succinimide, and the solvent was removed in vacuo. The crude product was recrystallized from hot DCM to afford small white needle like crystals (0.298 g, 42%). 1 H NMR (300 MHz, CDCl 3 ): 8.68 (d, J = 2.0 Hz, 2H), 8.40 (d, J = 8.3 Hz, 2H), 7.86 (dd, J = 8.2, 2.3 Hz, 2H), 4.54 (s, 4H). This compound was characterized by comparison to literature data 63 L1. To a 25 mL Schlenk flask containing bpy1 (0.174 g, 0.661 mmol), dpa (237 2 CO 3 (0.367 g, 2.65 mmol), and Bu 4 NI (catalytic amount) was added 12 mL anhydrous THF. The mixture was stirred for 17 h at room temperature resulting in a cl oudy orange mixture containing a fine white precipitate which was removed by filtration. The solvent was removed from the filtrate and the resulting off white solid was purified by column chromatography on neutral alumina using 0 50% EtOAc in DCM yieldin g L1 as an off white powder (0.203 g, 80%). 1 H NMR (300 MHz, CDCl 3 J = 2.0 Hz, 1H), 8.54 (d, J = 5.5 Hz, 2H), 8.50 (d, J = 2.2 Hz, 1H), 8.30 (d, J = 8.2 Hz, 1H), 8.25 (d, J = 8.2 Hz, 1H), 7.84 (dd, J = 8.2, 2.2 Hz, 1H), 7.68 (td, J = 7.7, 1.7 Hz, 2H), 7.62 (dd, J = 8.4, 2.0 Hz, 1H), 7.57 (d, J = 8.0 Hz, 2H), 7.17 (ddd, J = 7.2, 5.0. 1.1 Hz, 2H), 3.86 (s, 4H), 3.76 (s, 2H), 2.40 (s, 3H). This compound was characterized by comparison to literature data 63 L2. Dpa (1.17 mL, 1.30 g, 6.50 mmol), bpy2 (0.743 g, 2.17 mmol), and K 2 CO 3 (2.40 g, 17.4 mmol) were added to a 100 mL Schlenk flask. The reagents were suspended in 43 mL anhydrous THF, and the reaction mixture was stirred at room temperature for 22 h. An off white solid was removed by filtration, and 128 mL of hexane was added to the filtrate. The solution was placed in a 200 mL Schlenk flask and left under argon for 3 days at which point flat, needle like crystals had formed.

PAGE 113

113 These tan crystals (0.907 g, 72% ) were collected by vacuum filtration. 1 H NMR (300 MHz, CDCl 3 J = 1.5 Hz, 2H), 8.53 (ddd, J = 4.9, 1.9, 1.0 Hz, 4H), 8.31 (d, J = 8.5 Hz, 2H), 7.84 (dd, J = 8.0, 2.2 Hz, 2H), 7.67 (td, J = 7.6, 1.8 Hz, 4H), 7.56 (d, J = 7.9 Hz, 4H), 7.16 (ddd J = 7.4, 4.9, 1.2 Hz, 4H), 3.85 (s, 8H), 3.76 (s, 4H). 13 C NMR (300 MHz, CDCl 3 60.3, 55.9. This compound was characterized by comparison to literature data 63 L1'. 4 Bromomethyl 2,2' biphenyl (0.534 g, 2.16 mmol), K 2 CO 3 (1.192 g, 8.62 mmol), and Bu 4 NI (roughly 10 mg) were combined with anhydrous THF (40 mL) and dpa (0.58 mL, 3.24 m mol) in a 100 mL Schlenk flask. After stirring at room temperature overnight, the reaction mixture was filtered to remove a tan solid impurity. The solvent of the filtrate was removed to give a brown oil/solid mixture which was purified by column chromat ography on neutral alumina using ethyl acetate as eluent. The product was collected as a pale yellow oil (0.683 g, 86%). 1 H NMR (300 MHz, CDCl 3 (d, J = 4.7 Hz, 2H), 7.70 7.30 (m, 13H), 7.10 7.20 (m), 3.85 (s, 4H), 3.74 (s, 2H). 13 C 129.0, 127.9, 127.5, 127.4, 127.3, 127.2, 123.3, 122.5, 59.8, 58.4. No te: This product slowly develops a yellowish brown tint while being stored under vacuum but can be used for further synthesis. L2'. THF (20 mL) and dpa (0.67 mL, 3.72 mmol) were added to a 50 mL Schlenk flask containing bpy2 (0.506 g, 1.49 mmol), K 2 CO 3 (1 .63 g, 11.8 mmol), and Bu 4 NI (catalytic amount) to give a yellow mixture. After stirring at room temperature overnight the mixture had darkened to an orange brown color and was filtered to remove an off white solid impurity. Hexanes (80 mL) were added t o the orange filtrate to precipitate a

PAGE 114

114 tan crystalline solid which was collected by filtration. The crude product was dissolved in minimum DCM and recrystallized by addition of hexanes to give a tan crystalline solid (0.608 g, 71%). 1 H NMR (300 MHz, CDCl 3 J = 4.8, 1.7, 1.0 Hz, 4H), 7.68 (td, J = 7.4, 1.7 Hz, 4H), 7.61 (dt, J = 7.4, 1.0 Hz, 4H), 7.57 7.42 (m, 8H), 7.15 (ddd, J = 7.2, 5.0, 1.5 Hz, 4H), 3.84 (s, 8H), 3.73 (s, 4H). This compound was characterized by comparison to literature da ta 69 L2'' 5,5' Di(bromomethyl) 2,2' bipyridyl (0.174 g, 0.510 mmol), K 2 C O 3 (0.563, 4.08 mmol), and approximately 10 mg of Bu 4 NI were reacted with dibenzylamine (0.24 mL, 1.3 mmol) in anhydrous THF (10 mL) in a 100 mL round bottom flask. After stirring at room temperature overnight, the yellow mixture became white and was filt ered to remove the white solid impurity. The solvent was removed from the filtrate to give another white solid. The crude product was washed with CH 3 OH (15 mL) to give the product as a white powder (0.2154 g, 74%). 1 H NMR (300 MHz, CDCl 3 J = 1.6 Hz, 2H), 8.31 (d, J = 8.2 Hz, 2H), 7.82 (dd, J = 8.2, 2.2 Hz, 2H), 7.45 7.16 (m, 20H), 3.61 (s, 4H), 3.58 (s, 8H). 13 C NMR (75 MHz, CDCl 3 135.2, 129.0, 12 8.6, 127.3, 120.8, 58.2, 55.2. Syntheses of Mod el Complexes Alternative synthetic methods for the preparation of [Pd(dpa)Cl]Cl and [Pt(dpa)Cl]Cl have been previously reported In these reports, the [Pd(dpa)Cl]Cl complex was characterized by X ray crystallography and elemental analysis only, 131 and the [Pt(dpa)Cl]Cl complex was characterized by elemental analysis and 1 H NMR in D 2 O. 132 The Zn(dpa)Cl 2 complex was also previously reported with X ray crystal data and with 1 H and 13 C NMR data in DMSO d 6 133

PAGE 115

115 [Rh(bpy0)COD]Cl (52). To a 50 mL Schlenk flask containing bpy0 ( 0.0786 g, 0.427 mmol) and [Rh (COD)Cl] 2 (0.1029 g, 0.209 mmol) was added 20 mL anhydrous THF. The reactants dissolved immediately into a red orange s olution. Within seconds a neon orange solid precipitated. The mixture was allowed to stir overnight, and the solvent was removed in va cuo leaving a neon orange solid (0.154 g, 86%). 1 H NMR (300 MHz, CDCl 3 J = 8.2 Hz, 2H), 8.08 (dd, J = 8.3, 1.4 Hz, 2H), 7.51 (s, 2H), 4.49 (br s, 4H), 2.74 2.53 (m, 4H), 2.42 (s, 6H), 2.24 2.05 (m, 4H). 13 C NMR C 20 H 24 ClN 2 Rh : C, 55.76; H, 5.62; N, 6.50. Found: C, 55.62; H, 5.71; N, 6.33. [(dpa)ZnCl 2 ] (61) This synthesis was modified from that of Zhu and coworkers. 63 ZnCl 2 (0.1067 g, 0.783 mmol) was dissolved in methanol (2.5 mL) under ambient atmosphere. Upon addition of d pa (0.14 mL, 0.78 mmol), a white precipitate formed and was collected by vacuum filtration (0.1969 g, 75%). 1 H NMR (300 MHz, CD 3 J = 5.0 Hz, 2H), 8.02 (td, J = 7.7, 1.7 Hz, 2H), 7.55 (m, 4H), 4.47 (d, J = 15.2 Hz, 2H), 4.00 (d, J = 15.2 Hz, 2H). [(dpa)PdCl]Cl (62) Pd(COD)Cl 2 (0.0810 g, 0.284 mmol) was dissolved in THF (16 mL) under ambient atmosphere. D pa (0.05 mL, 0.3 mmol) was added re sulting in formation of a tan precipitate which was collected by vacuum filtration (0.0964 g, 92%). 1 H NMR (300 MHz, CD 3 J = 5.7, 1.6, 0.7 Hz, 2H), 8.08 (td, J = 7.8, 1.6 Hz, 2H), 7.60 (ddd, J = 8.0, 1.4, 0.7 Hz, 2 H), 7.50 (m, 2H), 4.95 (d, J = 16.2 Hz, 2H), 4.41 (d, J = 15.8 Hz, 2H). [(dpa)PtCl]Cl (63) Na 2 [PtCl 4 2 O (0.0290 g, 0.0757 mmol) was dissolv ed in DMSO d 6 (1 mL) under ambient atmosphere. D pa (0.02 mL, 0.1 mmol) was added

PAGE 116

116 yielding a vibrant green reaction mixture. After 20 hours of stirring at room temperature, the reaction mixture consisted of a white precipitate suspended in a bright yellow solution The solid was collected by vacuum filtration and washed with diethylether (0.0306 g, 87%). 1 H NMR (300 MHz, CD 3 (td, J = 7.9, 1.5 Hz, 2H), 7.67 (ddd, J = 8.0, 1.3, 0.7 Hz, 2H), 7.55 (m, 2H), 4.65 (d, 16.0 Hz, 2H). Syntheses of Monometallic and Homobimetallic Complexes of L1 and L2 (L1)ZnCl 2 (41). This synthesis was modi fied from that of Zhu and coworkers but spectral data were not previously reported 63 Ligand L1 (0.3017 g, 0.790 mmol) was dissolved in CH 2 Cl 2 (6.0 mL) and was a dded to a CH 3 CN (10.0 mL) solution of ZnCl 2 (0.1078 g, 0.790 mmol). The solvent was immediately removed by rotary evaporation to give a white powder (0.3842 g, 94%). 1 H NMR (500 MHz, CDCl 3 J = 5.4, 1.0 Hz, 2H), 8.51 (d, J = 1.9 Hz, 1H), 8.40 (d, J = 1.9 Hz, 1H), 8.30 (d, J = 7.8 Hz, 1H), 8.23 (d, J = 8.3 Hz, 1H), 7.91 (td, J = 7.7, 1.7 Hz, 2H), 7.66 (dd, J = 8.2, 1.9 Hz 2H ), 7.64 (dd, J = 8.2, 1.9 Hz, 2H), 7.52 (ddd, J = 7.4, 5.2, 1.0 Hz, 2H), 7.34 (d, J = 7.8 Hz, 2H), 4.11 (br s, 4H), 3.90 (s, 2H), 2.42 (s, 3H). 13 C NMR (126 MHz, CDCl 3 ): 156.3, 153.4, 152.4, 150.7, 150.5, 149.8, 140.2, 139.6, 137.7, 134.2, 127.4, 124.8, 123.7, 120.6, 120.6, 55.5, 53.0, 18.5. (L2)(Zn(OAc) 2 ) 2 (42). A methanolic solution of Zn(OAc) 2 2 O (0.0124 g, 0.0565 mmol) was added to a methanolic solution of L2 (0.0186 g, 0.0321 mmol) open to air. The solvent was removed under reduced pressure to afford 4 2 as a pale yellow solid (0.0163 g, 61%). 1 H N MR (300 MHz, CD 3 J = 4.2 Hz, 4H), 8.55 (br s, 2H), 8.36 (d, J = 7.6 Hz, 2H), 8.06 (t, J = 7.5 Hz, 4H), 7.94 (br s, 2H), 7.61 (t, J = 6.3 Hz, 4H), 7.56 (d, J = 8.0 Hz, 4H), 4.36 3.99 (m, 8H), 3.90 (br s, 4H), 2.01 (s, 11H). 13 C

PAGE 117

117 NMR (126 MHz, CD 3 OD): 179.3 154.8, 151.1, 148.6, 140.6, 140.0, 128.8, 124.6, 124.2, 120.7, 55.4, 53.2, 21.8. [(L2)(Zn(NO 3 ) 2 ) 2 ] (43). L2 (0.0168 g, 0.0290 mmol) and Zn(NO 3 ) 2 2 O (0.0170 g, 0.0571 mmol) were both added to a 25 mL round bottom flask and dissolved in methanol under a mbient atmosphere. As soon as all reagents had dissolved, the solvent was removed under reduced pressure to afford 43 as a pale yellow solid (0.0146 g, 53%). 1 H NMR (300 MHz, CD 3 J = 5.1 Hz, 4H), 7.43 (d, J = 1.7 Hz, 2H), 7.31 (d, J = 7.4 Hz, 2H), 7.06 (td, J = 7.3, 1.3 Hz, 4H), 6.76 (dd, J = 7.6, 2.0 Hz, 2H), 6.66 6.54 (m, 8H), 3.27 (d, J = 15.0 Hz, 4H), 2.87 (d, J = 16.4 Hz, 4H), 2.71 (s, 4H). This compound was characterized by comparison to literature data 65 [(L1)(PtCl)](PF 6 ) ([44](PF 6 )). Na 2 [PtCl 4 2 O (0.0231 g, 0.0606 mmol) and L1 (0.0232 g, 0.0606 mmol) were suspended in 1.5 mL DMSO d 6 and allowed to stir at room temperature overnight. Addition of 16 mL acetone resulted in the precipi tation of an NMR silent impurity (most likely NaCl) which was removed by filtration. The acetone was removed from the filtrate by rotary evaporation. Excess aqueous KPF 6 was added to the yellow residue yielding the product as an off white solid (0.0440 g 96%) which was collected by vacuum filtration and washed with methanol and diethyl ether. 1 H NMR (300 MHz, DMSO d 6 ): 8.98 (s, 1H), 8.64 (d, J = 5.4 Hz, 2H), 8.48 (s, 1H), 8.30 (d, J = 7.3 Hz, 1H), 8.11 (d, J = 8.2 Hz, 1H), 8.10 (t, J = 8.4 Hz, 2H), 7.99 (d, J = 8.0 Hz, 1H), 7.73 (d, J = 8.8 Hz, 1H), 7.68 (d, J = 7.9 Hz, 2H), 7.52 7.42 (m, 2H), 5.42 (d, J = 15.6 Hz, 2H) 4.99 (d, J = 16.2 Hz, 2H), 4.45 (s, 2H), 2.35 (s, 3H). 13 C NMR (126 MHz, DMSO d 6 ): 165.9, 156.0, 153.3, 152.3, 150.1, 149.5, 141.6, 141.4, 138.1, 134.6, 127.7, 125.4, 124.1, 120.8, 119.3, 68.4, 64.3, 18.3. HRMS (ESI TOF) for

PAGE 118

118 C 24 H 23 ClF 6 N 5 PPt: calcd. [M PF 6 ] + 612.1281, found 612.1287. Anal. Calcd for C 24 H 23 ClF 6 N 5 PPt: C, 38.08; H, 3.06; N, 9.25. Found: C, 38.12; H, 3.08; N, 9.22. [(L2)(PtCl) 2 ]Cl 2 ([45]Cl 2 ). A 50 mL Schlenk flask was charged with L2 (0.3027 g, 0.523 mmol), Na 2 [PtCl 4 2 O (0.4009 g, 1 .05 mmol), and anhydrous DMSO (20 mL) giving a dark burnt orange mixture. After stirring at room temperature overnight, the reaction produced a white solid suspended in a yellow solution. The reaction mixture was filt ered in air through a fine frit to af ford the product as a white powder (0.490 g, 84%). 1 H NMR (300 MHz, DMSO d 6 ): 8.90 (s, 2H), 8.64 (d, J = 5.5 Hz, 4H), 8.35 (d, J = 8.3 Hz, 2H), 8.13 (t, J = 7.7 Hz, 4H), 7.87 (d, J = 8.3 Hz, 2H), 7.71 (d, J = 7.7 Hz, 4H), 7.55 7.45 (m, 4H), 5.51 (d, J = 16.0, 4H), 5.00 (d, J = 14.9, 4H), 4.41 (br s, 4H). 13 C NMR (126 MHz, DMSO d 6 ): 165.9, 154.8, 153.4, 149.5, 141.8, 141.3, 128.7, 125.4, 124.1, 120.0, 68.5, 64.3. HRMS (ESI TOF) for C 36 H 34 Cl 4 N 8 Pt 2 : calcd. [M 2Cl] 2+ 519.5779, found 519.5785. [(L2)(PtCl) 2 ](PF 6 ) 2 ([45](PF 6 ) 2 ). Complex [ 45 ]Cl 2 (0.0505 g, 0.0455 mmol) was dissolved in DMSO/H 2 O (5:3) and treated with excess aqueous KPF 6 (sat.). The white precipitate was collected by vacuum filtration and washed with methanol and diethyl ether (0.0283 g, 47%) The product was insoluble in all available deuterated NMR solvents. Anal. Calcd for C 36 H 34 Cl 2 F 12 N 8 P 2 Pt 2 : C, 32.50; H, 2.58; N, 8.43. Found: C, 32.59; H, 2.67; N, 8.34. [(L1)PdCl]PF 6 ([46]PF 6 ). L1 (0.0213 g, 0.0558 mmol) and Pd(COD)Cl 2 (0.0151 g, 0.05 29 mmol) were dissolved in methanol (10 mL) and allowed to stir overnight. Solvent was removed from the resulting pale yellow solution, and the pale yellow residue was redissolved in 1 mL of CD 3 OD for NMR characterization revealing product

PAGE 119

119 [ 46 ]Cl and trac e amounts of L1. Addition of 0.425 M aqueous KPF 6 (0.25 mL, 0.11 mmol) to this solution resulted in precipitation of [ 46 ]PF 6 The product was collected by vacuum filtration and washed with diethylether yielding a white powder (0.0274 g, 78%). 1 H NMR (30 0 MHz, DMSO d 6 ): 9.05 (s, 1H), 8.49 (s, 1H), 8.42 (d, J = 5.7 Hz, 2H), 8.36 (d, J = 8.5 Hz, 1H), 8.13 (d, J = 8.3 Hz, 1H), 8.07 (t, J = 7.7 Hz, 2H), 8.04 (d, J = 7.7 Hz, 1H), 7.74 (d, J = 7.7 Hz, 1H), 7.65 (d, J = 7.7 Hz, 2H), 7.45 (m, 2H), 5.58 (d, J = 16.1 Hz, 2H), 4.70 (d, J = 16.2 Hz, 2H), 4.39 (s, 2H), 2.35 (s, 3H). For the more soluble Cl salt from gHMBCAD data. 13 C NMR (126 MHz, CD 3 OD): 164.6, 156.4, 152.2, 151.9, 150.4, 149.3, 141.0, 140.8, 137.8, 134.8, 128.0, 124.3, 123.1, 120.9, 120.0, 67. 4, 63.7, 16.8. HRMS (ESI TOF) for C 24 H 23 Cl 2 N 5 Pd: calcd. [M Cl] + 524.0670, found 524.0682. [(L2)(PdCl) 2 ]Cl 2 ([47]Cl 2 ). A 100 mL Schlenk flask was charged with Pd(COD)Cl 2 (0.0990 g, 0.347 mmol) and L2 (0.100 g, 0.173 mmol). The reagents were combined wit h 60 mL anhydrous THF. The reaction mixture was stirred for 24 h, at which point a white precipitate had formed. The supernatant was removed and the solid was rinsed with anhydrous THF (20 mL) to yield [ 47 ]Cl 2 as an off white powder (0.150 g, 93%). 1 H N MR (300 MHz, CD 3 OD): 9.08 (d, J = 1.7 Hz, 2H), 8.58 (dd, J = 5.8, 1.0 Hz, 4H), 8.45 (dd, J = 8.2, 2.3 Hz, 2H), 8.01 (td, J = 7.8, 1.5 Hz, 2H), 7.97 (d, J = 8.8 Hz, 4H), 7.60 (d, J = 7.9 Hz, 4H), 7.41 (ddd, J = 7.2, 5.7, 1.0 Hz, 4H), 5.53 (d, J = 16.1 Hz, 4H), 4.73 (d, J = 15.5 Hz, 4H), 4.42 (s, 4H). 13 C NMR (126 MHz, CD 3 OD): 164.6, 155.3, 152.4, 150.5, 141.1, 141.0, 128.9, 124.4, 123.2, 120.5, 67.4, 63.6. HRMS (ESI TOF) C 36 H 34 Cl 4 N 8 Pd 2 : calcd. [M 2Cl] 2+ 431.0175, found 431.0165; calcd. [M Cl] + 897.003 9, found 897.0040; calcd. [M HCl 2 ] + 861.0277, found 861.0270.

PAGE 120

120 [(L2)(PdCl) 2 ](PF 6 ) 2 ([47](PF 6 ) 2 ). Complex [ 47 ]Cl 2 (0.0207 g, 0.0222 mmol) was dissolved in 4 mL of methanol. Upon addition of excess KPF 6 the product precipitated and was collected by vacuum filtration. After washing with methanol and ether, the product was collected as an off white solid (0.0127 g, 50%). 1 H NMR (300 MHz, DMSO d 6 ): 8.99 (s, 2H), 8.38 (d, J = 5.3 Hz, 4H), 8.33 (d, J = 7.4 Hz, 2H), 8.02 (t, J = 7.7 Hz, 4H), 7.87 (d, J = 8.3 Hz, 2H), 7.60 (d, J = 8.0 Hz, 4H), 7.41 (t, J = 6.8 Hz, 4H), 5.54 (d, J = 15.8 Hz, 4H), 4.66 (d, J = 16.1 Hz, 4H), 4.33 (s, 4H). Anal. Calcd for C 36 H 34 Cl 2 F 12 N 8 P 2 Pd 2 : C, 37.52; H, 2.97; N, 9.72. Found: C, 37.46; H, 3.04; N, 9.68. [(L2')(PtCl) 2 ]Cl 2 ([48]Cl 2 ). L2' (0.0205 g, 0.0350 mmol) and Na 2 [PtCl 4 2 O (0.0269 g, 0.0702 mmol) were each combined separately with 1 mL DMSO d 6 The Na 2 [PtCl 4 2 O suspension was added to the ligand solution, and the reaction mixture was allowed to stir at room temperature. NMR analysis revealed the reaction mixture to have reached equilibrium when a ratio of 1.0:0.27 [ 48 ]Cl 2 :L2' was present. Addition of excess a queous KPF 6 (sat.) did not result in formation of a precipitate. 1 H NMR (300 MHz, DMSO d 6 ): 8.57 (dd, J = 5.8, 1.0, 4H), 8.05 (td, J = 7.8, 1.5 Hz, 4H), 7.79 (d, J = 8.3 Hz, 4H), 7.60 (d, J = 7.9 Hz, 4H), 7.47 7.42 (m, 4H), 7.06 (d, J = 8.2 Hz, 4H), 5.4 7 (d, J = 15.9 Hz, 4H), 4.98 (d, J = 15.9 Hz, 4H), 4.35 (s, 4H). The 1 H NMR data were obtained from a mixture with L2' starting material but only the signals from [ 4 8 ]Cl 2 were reported. [(L2')(PdCl) 2 ]Cl 2 ([49]Cl 2 ). Anhydrous THF (20 mL) was added to a 50 mL Schlenk flask containing Pd(COD)Cl 2 (0.0199 g, 0.0697 mmol) and L2' (0.0202 g, 0.0350 mmol). The yellow solution quickly began to form a white precipitate. After allowing the reaction mixture to stir overnight at room temperature, the precipitate was

PAGE 121

121 allowed to settle and the supernatant was removed. The white product was washed once with 20 mL anhydrous THF to afford pure product (0.0220 g, 69%). 1 H NMR (300 MHz, CD 3 OD); 8.57 (dt, J = 5.9, 0.8 Hz, 4H), 8.02 (td, 7.8, 1.1 Hz, 4H), 7.93 (d, J = 8.2 Hz, 4H), 7.55 (d, J = 7.9 Hz, 4H), 7.44 (t, J = 6.8 Hz, 4H), 7.22 (d, J = 8.2 Hz, 4H), 5.48 (d, J = 15.9 Hz, 4H), 4.66 (d, J = 15.9 Hz, 4H), 4.31 (s, 4H). 13 C NMR (126 MHz, CD 3 OD): 164.8, 150.3, 141.1, 140.8, 132.8, 131.4, 126.9, 124.1, 123.0, 67.5, 66 .4. HRMS (ESI TOF) for C 38 H 36 Cl 4 N 6 Pd 2 : calcd. [M HCl 2 ] + 859.0373, found 859.0397; calcd. [M H 2 Cl 3 ] + 823.0612, found 823.0634. [(COD)Rh(L1)]Cl (50). To a 25 mL Schlenk flask containing L1 (0.0392 g, 0.103 mol) and [Rh(COD)Cl] 2 (0.0268 g, 0.0544 mmol) was added 16 mL of anhydrous THF. The mixture was allowed to stir at room temperature for one hour at which point 1 H NMR indicated conversion to product with a small amount of L1 still present. The solvent was removed by reduced pressure yielding 0.0569 g ( 88% crude yield) of a rust colored powder. Longer reaction times did not yield further conversion, and overnight reaction resulted in discoloration of the product to a dark wine red color. Purification by recrystallization from anhydrous CH 2 Cl 2 and hexan es was unsuccessful. Performing the same procedure in refluxing toluene resulted in no reaction while the room temperature reaction in EtOH yielded the same product as the THF reaction. 1 H NMR (300 MHz, CDCl 3 ): 9.23 (d, J = 8.5 Hz, 1H), 9.16 (d, J = 8.5 Hz, 1H), 8.54 (d, J = 4.8 Hz, 2H), 8.25 (dd, J = 8.4, 1.7 Hz, 1H), 8.11 (dd, J = 8.5, 1.5 Hz, 1H), 7.88 (s, 1H), 7.71 (td, J = 7.7, 1.7 Hz, 2H), 7.49 (s, 1H), 7.47 (d, J = 7.5 Hz, 2H), 7.20 (d, J = 6.9, 5.3 Hz, 2H), 4.55 (br s, 3H), 3.83 (s, 4H), 3.74 (s, 2H), 2.70 2.45 (m, 4H), 2.41 (s, 3H), 2.22 2.10 (m, 4H). 13 C NMR (126 MHz, CDCl3): 158.1, 155.4, 154.1, 149.1, 148.0, 147.2,

PAGE 122

122 142.1, 141.6, 138.5, 137.4, 136.7, 125.1, 124.6, 123.4, 122.4, 84.2, 59.8, 54.2, 30.3, 18.6. Note that in the 1 H and 13 C NMR data listed here, only the peaks corresponding to product are listed, although the ligand L1 starting material was also present. HRMS (ESI TOF) for C 32 H 35 ClN 5 Rh: calcd. [M Cl] + 592.1942, found 592.1928. [(COD) Rh(L2)]Cl (51). [Rh(COD)Cl] 2 (0.149 g, 0.0302 mmol) was added along with L2 (0.362 g, 0.0302 mmol) to a 10 mL Schlenk flask The reagents were dissolved in 8 mL of anhydrous THF and stirred at room temperature for 45 min. The solvent was removed under reduced pressure, leaving the product as a shiny red solid which adhered strongly to the sides of the flask. Purification was attempted by recrystallization from CH 2 Cl 2 with hexanes and also from CH 2 Cl 2 with toluene. 1 H NMR (300 MHz, CDCl 3 ): 9.37 (d, J = 8.2 Hz, 2H), 8.53 (d, J = 4.2 Hz, 4H), 8.26 (d, J = 7.9 Hz, 2H), 7.86 (br s, 2H), 7.70 (t, J = 8.0 Hz, 4H), 7.47 (d, J = 7.9 Hz, 4H), 7.24 7.08 (m, 4H), 4.59 (br s, 4H), 3.82 (s, 8H), 3.73 (s, 4H), 2.74 2.50 (m, 4H), 2.28 2.19 (m, 4H). The 1 H and 13 C N MR data were obtained from a mixture with L2 starting material, but only the peaks for 5 1 were reported. 13 C NMR (126 MHz, CDCl 3 ): 158.1, 155.4, 149.1, 148.0, 141.7, 138.6, 136.7, 125.2, 123.4, 122.4, 84.3, 59.8, 54.3, 30.4. HRMS (ESI TOF) for C 44 H 46 ClN 8 Rh: calcd. [M Cl] + 789.2895, found 789.2914. Syntheses of Diamagnetic Heterometallic Complexes of L1 and L2 [(COD)Rh(L1)ZnCl 2 ]Cl ( 5 5 ). To a 50 mL Schlenk flask containing 41 (25.0 mg, 0.0483 mmol) and [Rh(COD)Cl] 2 (12.2 mg, 0.0247 mmol) was added 10 mL anhydrous THF resulting in an orange solution. A pink orange solid began to precipitate within three hours. The mixture was allow ed to stir at room temperature overnight at which point a 1 H NMR spectrum indicated full conversion to product. 1 H NMR (300 MHz, CDCl 3 J = 5.3 Hz, 2H), 8.98 (d, J = 8.3 Hz, 1H), 8.42 (s, 1H), 8.34 (d,

PAGE 123

123 J = 8.0 Hz, 1H), 8.31 (d, J = 8.0 Hz, 1H), 7.97 (d, J = 8.0 Hz, 1H), 7.72 (t, J = 8.0, 2H), 7.50 7.44 (m, 5H), 4.65 (d, J = 16 Hz, 2H), 4.57 (br s, 4H), 4.51 (s, 2H), 4 .01 (d, J = 16.0 Hz 2H ), 2.76 2.51 (m, 4H), 2.46 (s, 3H), 2.27 2.17 (m, 4H). 13 C NMR (126 MHz, CDCl 3 ): 155.6, 154.8, 153.7, 151.6, 149.7, 147.6, 144.7, 141.7, 140.3, 137.7, 134.7, 124.7, 124.1, 123.9, 123.4, 85.3, 57.0, 55.9, 30.3, 18.7. HRMS (ESI TOF ) for C 32 H 35 Cl 3 N 5 RhZn: calcd. [M Cl] + 728.0585, found 728.0608. Anal. Calcd for C 32 H 35 Cl 3 N 5 RhZn: C, 50.29; H, 4.62; N, 9.16. Found: C, 50.18; H, 4.58; N, 8.96. 2 (NO 3 ) 4 Cl ( 5 6 ). A solution of L2 (0.0160 g, 0.0276 mmol) in 5 mL methanol was prepared in a 25 mL round bottom flask open to air. To this was added a solution of Zn(NO 3 ) 2 2 O (0.0162 g, 0.0544 mmol) also dissolved in methanol. The solvent was removed under reduced pressure, and the round bottom flask was charged with argon. Anh ydrous THF was added to the flask, but not all of the solids dissolved. The white suspension was cannula transferred to a Schlenk flask containing an orange solution of [Rh(COD)Cl] 2 (0.0068 g, 0.014 mmol) in anhydrous THF. The reaction mixture turned yel low but not everything went into solution. Solvent was removed under reduced pressure, yielding 56 as a tan solid containing some unidentified impurities (0.0201 g, 61%). 1 H NMR (300 MHz, CD 3 J = 5.2, 1.3, 0.7 Hz, 4H), 8.32 (d, J = 8.2 Hz, 2H), 8.28 (dd, J = 8.5, 1.3 Hz, 2H), 8.14 (td, J = 7.6, 1.6 Hz, 4H), 7.90 (s, 2H), 7.74 (ddd, J = 8.0, 5.0, 0.9 Hz, 4H), 7.63 (d, J = 7.9 Hz, 4H), 4.68 (br s, 4H), 4.39 (br d, J = 16 Hz, 4H) 4.13 (s, 4H), 4.08 (br d, J = 20 Hz, 4H), 2.72 2.67 (m, 4H), 2.29 2.23 (m, 4H). The 1 H NMR data were obtained from an impure sample but only peaks from 56 were reported. 13 C NMR (126 MHz, CD 3 OD): 159.7, 159.0, 154.8, 152.2, 147.5, 145.7, 137.3, 129. 1, 129.0, 126.9, 60.2, 58.4, 33.9.

PAGE 124

124 3 ) 2 Cl ( 5 7 ). L1 (0.0206 g, 0.0540 mmol) and [Rh(COD)Cl] 2 were dissolved in anhydrous ethanol (8 mL) in a 25 mL Schlenk flask and allowed to stir at room temperature for 30 min A 5 mL ethanolic solutio n of Zn(NO 3 ) 2 2 O (0.0163 g, 0.0548 mmol) was then cannula transferred into the 25 mL Schlenk flask resulting in the immediate precipitation of a fine pink orange solid. The solvent was removed in vacuo and the product was collected as a dark brown red p owder containing some unidentified impurities (0.0368 g, 83%). 1 H NMR (300 MHz, CD 3 J = 4.8 Hz, 2H), 8.25 (d, J = 8.0 Hz, 2H), 8.18 (d, J = 8.0 Hz, 1H), 8.12 7.94 (m, 4H), 7.77 (s, 1H), 7.72 7.61 (m, 2H), 7.50 (d, J = 7.4 Hz, 2H), 4.66 (br s, 4H), 4.24 (br s, 4H), 4.18 (s, 2H), 2.80 2.52 (m, 4H), 2.45 (s, 3H), 2.36 2.13 (m, 4H). 13 C NMR (126 MHz, CD 3 OD): 156.2, 155.2, 153.1, 150.9, 149.0, 148.5, 143.3, 141.3, 141.2, 139.0, 133.4, 124.8, 124.5, 122.7, 122.0, 85.4, 556.7, 55.7, 29.8, 17.0. [(COD)Rh(L1)PdCl]Cl 2 ( 5 8 ). L1 (0.0509 g, 0.133 mmol) and [Rh(COD)Cl] 2 (0.0328 g, 0.0665 mmol) were dissolved in anhydrous EtOH (20 mL) in a 200 mL Schlenk flask and allowed to stir for 35 minutes. An 54 mL anhydrous ethanolic solution of Pd(COD)Cl 2 (0.0 165 g, 0.0578 mmol) was then cannula transferred into the reaction Schlenk flask. The reaction mixture was stirred at room temperature for 12 hours at which point the solvent was reduced to approximately 3 mL. The product was precipitated upon addition o f 40 mL of anhydrous diethylether, collected by filtration, and washed with anhydrous diethylether (10 mL). The product was collected as a brown red powder (0.0810 g, 75%). 1 H NMR (300 MHz, CD 3 OD): 8.83 (s, 1H), 8.64 (dd, J = 5.7, 1.2 Hz, 2H), 8.43 (dd J = 8.3, 1.9 Hz, 1H), 8.20 (d, J = 8.0 Hz, 1H), 8.12 7.96 (m, 4H), 7.79 (s, 1H), 7.64 (d, J = 7.9 Hz, 2H), 7.43 (m, 2H), 5.56 (d, J = 16.4 Hz, 2H), 4.86

PAGE 125

125 (br s, 4H), 4.80 (d, J = 16.1 Hz, 2H), 4.50 (s, 2H), 2.78 2.63 (m, 4H), 2.45 (s, 3H), 2.34 2.21 (m, 4 H). 13 C NMR (126 MHz, CD 3 OD, 20 C): 164.6, 156.6, 152.5, 150.3, 149.4, 143.9, 141.4, 141.2, 139.5, 132.2, 124.6, 123.5, 123.0, 122.0, 86.0, 67.2, 62.4, 30.0, 17.0. HRMS (ESI TOF) for C 32 H 35 Cl 3 N 5 PdRh: calcd. [M Cl] + 770.0350, found 770.0348. [(COD)Rh(L2)(PdCl) 2 ]Cl 3 ( 59 ). A 50 mL Schlenk f lask was charged with [Rh(COD)Cl] 2 (0.0106 g, 0.0215 mmol) and 4 7 (0.0400 g, 0.0429 mmol). The reagents were suspended in 30 mL of anhydrous ethanol. After 50 min, all reagents had dissolved into a red orange solution. Solvent was removed under reduced pressure giving 59 as a brown powder (0.0375 g, 79%). 1 H NMR (300 MHz, CD 3 OD): 8.84 (s, 2H), 8.63 (d, J = 5.4 Hz, 4H), 8.45 (dd, J = 8.3, 1.1 Hz, 2H), 8.05 (d, J = 2.3 Hz, 2H), 8.07 (td, J = 7.8, 1.5 Hz, 4H), 7.66 (d, J = 7.6 Hz, 2H), 7.49 (m, 4H), 5.56 (d, J = 16.4 Hz, 4H), 5.06 (br s, 4H), 4.83 (d, J = 16.4 Hz, 4H), 4.53 (s, 4H), 2.79 (m, 4H), 2.35 (m, 4H). 13 C NMR (126 MHz, CD 3 OD): 164.4, 155.2, 152.8, 150.5, 144.1, 141.4, 133.3, 124.7, 123.5, 123.0, 87.2, 67.4, 62.5, 30.0. HRMS (ESI TOF) for C 44 H 46 Cl 5 N 8 Pd 2 Rh: calcd. [M Cl] + 1144.9714, found 1144.9680; calcd. [M 2Cl] 2+ 554.00 15, found 554.0021. Anal. Calcd for C 44 H 46 Cl 5 N 8 Pd 2 Rh: C, 44.79; H, 3.93; N, 9.50. Found: C, 44.58; H, 4.02; N, 9.26. [(COD)Rh(L2)(PtCl) 2 ]Cl 3 ( 60 ). [Rh(COD)Cl] 2 (0.0 180 g, 0. 0 365 mmol) and [ 4 5 ]Cl 2 (0. 0 810 g, 0. 0 729 mmol) were dissolved in anhydrous metha nol ( 30 mL) in a 50 mL Schlenk flask. The bright orange solution became burnt orange red in color after stirring at room temperature for 2 hours. The solvent was reduced to approximately 10 mL, and anhydrous diethylether (40 mL) was added to precipitate the product. The

PAGE 126

126 solid was allowed to settle and the supernat a nt was removed followed by another 40 mL diethylether wash. The residual solvent was removed in vacuo yielding a pink brown solid (0.0 872 g, 88 %). 1 H NMR (300 MHz, CD 3 OD): 8.81 (d, J = 5.7 Hz, 4H), 8.77 (s, 2H), 8.40 (d, J = 7.9 Hz, 2H), 8.08 (t, J = 8.0 Hz, 4H), 7.98 (d, J = 8.0 Hz, 2H), 7.65 (d, J = 7.6 Hz, 4H), 7.55 7.42 (m, 4H), 5.37 (d, J = 15.9 Hz, 4H), 5.06 (d, J = 15.7 Hz, 4H), 4.99 (br s, 4H), 4.55 (s, 4H), 2.81 2.67 (m, 4H), 2.38 2.21 (m, 4H). 13 C NMR (126 Hz, CD 3 123.6, 122.9, 68.4, 63.2, 30.2. HRMS (ESI TOF) for C 44 H 46 Cl 5 N 8 Pt 2 Rh: calcd. [M Cl] + 1321.0922, found 1321.0920. Syntheses of Paramagnetic Heterometallic Complexes of L1 and L2 [Rh(COD)( L1)Cu(OTf) 2 ]Cl ( 65 ). Procedure A: Cu(OTf) 2 (0.0174 g, 0.0481 mmol) and L1 (0.0183 g, 0.0480 mmol) were dissolved in ethanol (6 mL) in a 50 mL Schlenk flask and allowed to stir for 15 minutes. A pale yellow 17 mL ethanolic solution of [Rh(COD)Cl] 2 (0.0118 g, 0.0239 mmol) was then cannula transferred into the Schlenk flask resulting in a color change from bright blue to amber brown. After an additional 1.75 h, the solvent was removed and the rust colored solid was collected (0.0273 g, 58%). P rocedure B: [R h(COD)Cl] 2 (0.0114 g, 0.0231 mmol) and L1 (0.0176 g, 0.0461 mmol) were dissolved in ethanol (7 mL) in a 50 mL Schlenk flask and allowed to stir for 50 minutes yielding an orange red solution. Cu(OTf) 2 (0.0167 g, 0.0462 mmol) was cannula transferred to the reaction Schlenk flask using 16 mL of ethanol immediately resulting in a brown red solution. Upon solvent removal in vacuo, the rust colored product was collected (0.0280 g, 61%). IR/cm 1 (neat): 1610 (w), 1574 (vw), 1504 (vw), 1478 (w), 1449 (w), 1413 ( vw), 1391 (vw), 1378 (vw), 1245 (s), 1223 (s), 1152 (s), 1101 (w), 1078 (w), 1054 (w), 1027 (s), 1001 (w), 961 (w), 896 (vw), 875 (w), 826 (w), 769

PAGE 127

127 (m), 726 (w), 655 (w). HRMS (ESI TOF) for C 34 H 35 ClCuF 6 N 5 O 6 RhS 2 calcd.: [M OTf] + 839.0447. Found: 839.042 4. Anal. Calcd for C 34 H 35 ClCuF 6 N 5 O 6 RhS 2 : C, 41.26; H, 3.56; N, 7.08. Found: C, 41.43; H, 3.68; N, 7.16. [Rh(COD)(L2)(Cu(OTf) 2 ) 2 ]Cl ( 66 ). P rocedure A: A 2 mL ethanolic solution of Cu(OTf) 2 (0.0270 g, 0.0746 mmol) was added to a 2 mL ethanolic solution of L2 (0.0216 g, 0.0373 mmol) in a 50 mL Schlenk flask to give a blue solution. After 15 min, a pale yellow 15 mL ethanolic solution of [Rh(COD)Cl] 2 (0.0092 g, 0.019 mmol) was cannula transferred into the Schlenk flask resulting in a color change from brig ht blue to dark grey. After an additional 1 h, the volume of the dark brown solution was reduced to less than 5 mL and diethyl ether was added resulting in precipitation of the product. The supernatant was removed and the product was washed with 30 mL of diethyl ether and collected as a brown powder (0.0439 g, 76%). Identical IR and EPR results were obtained when the reaction was performed in methanol. P rocedure B: [Rh(COD)Cl] 2 (0.0089 g, 0.018 mmol) and L2 (0.0209 g, 0.0361 mmol) were dissolved in etha nol (8 mL) in a 50 mL Schlenk flask and allowed to stir for 1 h yielding an orange red solution. Cu(OTf) 2 (0.0261 g, 0.0722 mmol) was cannula transferred to the reaction Schlenk flask using 2.6 mL of ethanol, which immediately resulted in a dark brown sol ution. The product was isolated as in P rocedure A to give a brown powder (0.0392 g, 70%). Repeating the reaction in methanol yielded identical results. IR/cm 1 (neat): 1612 (w), 1576 (vw), 1479 (w), 1450 (w), 1421 (vw), 1372 (vw), 1358 (vw), 1275 (s), 12 42 (s), 1224 (s), 1159 (s), 1102 (w), 1055 (w), 1027 (s), 1003 (w), 961 (w), 896 (vw), 878 (w), 863 (w), 818 (w), 770 (m), 727 (w). HRMS (ESI TOF) for C 48 H 46 ClCu 2 F 12 N 8 O 12 RhS 4 calcd.: [M Cu 4OTf] 2+ 443.5937. Found: 443.5931; calcd.: [M 2OTf + Cl] +

PAGE 128

128 1 284.9888. Found: 1284.9848. Anal. Calcd for C 48 H 46 ClCu 2 F 12 N 8 O 12 RhS 4 : C, 37.23; H, 2.99; N, 7.24. Found: C, 37.07; H, 3.03; N, 7.15. [Cu(OTf) 2 (L2)(PdCl) 2 ]Cl 2 ( 67 ). [(PdCl) 2 (L2)]Cl 2 (0.0214 g, 0.0229 mmol) and Cu(OTf) 2 (0.0092 g, 0.025 mmol) were each diss olved separately in 3.8 mL and 1.7 mL respectively of methanol. The Cu(OTf) 2 solution was added to the other to give a pale green solution. The reaction mixture was stirred as a mint green precipitate formed. The solid was collected by vacuum filtratio n and washed with diethyl ether to give mint green powder (0.0144 g, 49%). IR/cm 1 (neat): 1610 (w), 1576 (vw), 1480 (w), 1450 (w), 1412 (vw), 1389 (vw), 1273 (s), 1250 (s), 1223 (s), 1155 (s), 1054 (w), 1029 (s), 937 (w), 904 (vw), 875 (w), 826 (m), 815 (w), 765 (m), 723 (w), 679 (w). HRMS (ESI TOF) for C 38 H 34 Cl 4 CuF 6 N 8 O 6 Pd 2 S 2 calcd.: [M 2OTf Cl] 3+ 320.6438. Found: 320.6434; calcd.: [M OTf] + 1145.8505. Found: 1145.8529. Anal. Calcd for C 38 H 34 Cl 4 CuF 6 N 8 O 6 Pd 2 S 2 : C, 35.24; H, 2.65; N, 8.65. Found: C, 35.0 7; H, 2.60; N, 8.57. [Cu(OTf) 2 (L2)(PtCl) 2 ]Cl 2 ( 6 8 ). A 1.5 mL methanolic solution of Cu(OTf) 2 (0.0114 g, 0.0315 mmol) was added to a 7 mL methanolic solution of [ 47 ]Cl 2 (0.0318 g, 0.0286 mmol) resulting in the immediate precipitation of a mint green solid. After stirring for 15 min, the product was collected by vacuum filtration and washed with 0.7 mL of N 2 chilled methanol to give a mint green powder (0.0261 g, 62%). IR/cm 1 (neat): 1615 (w) 1571 ( v w) 1480 (w) 1449 (m) 1419 ( v w) 1403 ( v w) 1392 ( v w ) 1377 ( v w) 1258 (s) 1224 (m) 1153 (s) 1078 ( v w) 1059 (w) 1048 (w) 1029 (s) 1011 (w) 969 (w) 955 (w) 933 (w) 898 ( v w) 850 (w) 825 (m) 769 (s) 723 (m) 675 (w) HRMS (ESI TOF) for C 38 H 34 Cl 4 CuF 6 N 8 O 6 Pt 2 S 2 calcd.: [M 2OTf Cl] 3+ 379.3508. Found: 379.3505; [M OTf 2Cl] 3+ 417.3453. Found: 417.3451;. calcd.: [M Cl] + 1435.9573. Found:

PAGE 129

129 1436.9535; calcd.: [M 2Cl] 2+ 700.4942. Found: 700.4937; calcd.: [M 2OTf] 2+ 586.5106. Found: 586.5103. Anal. Calcd for C 38 H 34 Cl 4 CuF 6 N 8 O 6 Pt 2 S 2 : C, 31.00; H 2.33; N, 7.61. Found: C, 30.92; H, 2.32; N, 7.65. [Cu(OTf) 2 (L1)PdCl]Cl ( 6 9 ). Cu(OTf) 2 (0.0168 g, 0.0464 mmol) was dissolved in 1.5 mL of methanol and added to a 1 mL solution of [ 46 ]Cl (0.0260 g, 0.0465 mmol). The resulting kelly green solution was re duced to 1 mL in vacuo, and the product precipitated upon addition of diethyl ether. The deep mint green product was collected by vacuum filtration and washed with diethyl ether (0.0320 g, 75%). IR/cm 1 (neat): 1611 (w), 1572 (w), 1483 (w), 1450 (w), 142 0 (w), 1393 (w), 1376 (w), 1275 (s), 1255 (s), 1225 (s), 1163 (m), 1153 (m), 1112 (w), 1084 (w), 1056 (w), 1031 (s), 938 (w), 900 (w), 865 (w), 824 (w), 770 (m), 722 (w). HRMS (ESI TOF) for C 26 H 23 Cl 2 CuF 6 N 5 O 6 Pd S 2 calcd.: [M OTf Cl] 2+ 367.9739. Found: 36 7.9738; calcd.: [M OTf] + 770.9167. Found: 770.9156; calcd.: [M Cl] + 884.9002. Found: 884.8986. Anal. Calcd for C 26 H 23 Cl 2 CuF 6 N 5 O 6 PdS 2 : C, 33.93; H, 2.52; N, 7.61. Found: C, 34.07; H, 2.48; N, 7.58. [Pd(L1) 2 (Cu(OTf) 2 ) 2 ]Cl 2 ( 71 ). L1 (0.0251 g, 0.0658 mm ol) was dissolved in 2 mL of methanol and reacted with a 2 mL methanolic solution of Cu(OTf) 2 (0.0238 g, 0.0658 mmol) resulting in a dark blue solution. Upon addition of Pd(COD)Cl 2 (0.0188 g, 0.0659 mmol) dissolved in 5 mL of methanol, the reaction soluti on became turquoise teal. A fine precipitate began to form within 5 min, and was collected by filtration after 4 h. The grayish teal powder was washed with diethyl ether (0.0254 g, 42%). IR/cm 1 (neat): 1611(m), 1575 (w), 1475 (m) 1449 (m), 1413 (w), 13 89 (vw), 1354 (vw), 1364 (vw), 1254 (s), 1224 (m), 1153 (s), 1100 (w), 1084 (w), 1056 (m), 1029 (s), 1001 (w), 965 (w), 945 (w), 931 (w), 900 (w), 879 (w), 844 (m ), 817 (m), 769 (m), 761 (m), 708 (w), 684

PAGE 130

130 (w), 656 (m). HRMS (ESI TOF) for C 52 H 46 Cl 2 Cu 2 F 12 N 10 O 12 PdS 4 calcd.: [M L1 Cu 4OTf] 2+ 310.9821. Found: 310.9822; calc.: [M L1 Cu 3OTf Cl] 2+ 367.9739. Found: 367.9748; calc.: [M L1 Cu 3OTf] + 770.9167. Found: 770.9161. Anal. Calcd for C 52 H 46 Cl 2 Cu 2 F 12 N 10 O 12 PdS 4 : C, 37.54; H, 2.79; N, 8.42 Found: C, 37.89; H, 2.48; N, 8.76. Synthesis of L3 Complexes General synthetic procedure. A typical procedure for the reactions listed in Table 5 1 began with dissolving L3 (0.0500 g, 0.211 mmol) in 5 mL of solvent in a 4 dram vial. A 2 mL solution of o ne half equivalent of the first metal source (0.105 mmol) would then be added to the ligand solution followed by addition of a 2 mL solution of one half equivalent of the second metal source. The solution was left to stir for one hour, concentrated, and s et up for crystallization by vapor diffusion with a second solvent. trans [Cu(Cl) 2 (L3) 2 ] ( 72 ). CuCl 2 2 O (0.0182 g, 0.107 mmol) was dissolved in minimum MeOH and added dropwise to a vial containing L3 (0.0504 g, 0.212 mmol) dissolved in minimum amount of MeOH. The solvent was removed from the resulting blue solution, and the blue product was washed with Et 2 O. The product was then redissolved in minimum MeOH for vapor diffusion with Et 2 O. After several days, square blue crystals were formed and examined by X ray crystallography. [Cu(Cl)(L3) 2 ]Cl ( 73 ). CuCl 2 2 O (0.0180 g, 0.106 mmol) was dissolved in minimum MeOH and added dropwise to a vial containing L3 (0.0500 g, 0.211 mmol) dissolved in minimum amount of MeOH. The resulting teal solution was stirred at room temperature for 2 h The solvent was then reduced and the residue was set up for vapor

PAGE 131

131 diffusion with Et 2 O. Large teal needle shaped crystals formed and were examined by X ray crystallography. [CuCl(L3)] 2 ( 74 ). CuCl 2 2 O (0.0181 g, 0.106 mmol) and L3 (0.0500 g, 0.211 mmol) were dissolved in a minimum amount of MeOH to give a turquoise solution which was stirred at room temperature for 10 minutes. CoCl 2 2 O (0.0138 g, 0.106 mmol) was then dissolved in minimum MeOH and added dropwise to the reaction flask whose color became aqua blue. The solvent was removed to give 69.2 mg of aqua blue powder. A third of this was dissolved in minimum MeOH and set up for vapor diffusion with Et 2 O. Small aqua blue crystals formed and were examined by X ray crystallogra phy. trans [Co(Cl) 2 (L3) 2 ] ( 75 ). CoCl 2 (0.0150 g, 0.116 mmol) was dissolved in 1 mL MeOH and added dropwise to a vial containing 4 mL of a MeOH solution of L3 (0.0500 g, 0.211 mmol). The purple blue solution was allowed to stir for 1h A 1 mL MeOH solution of CuCl 2 2 O was then added, and the mix ture was allowed to stir for an additional two hours. The solvent was reduced by rotary evaporation and the residue was set up for vapor diffusion with Et 2 O. Peach colored crystals formed and were analyzed by X ray crystallography. Kinetic Studies of H/D Exchange in Rh/Pd and Rh/Pt Complexes A 4.9 mg sample of complex 60 was dissolved in 0.70 mL of CD 3 OD at a time designated t = 0 s. Using a 300 MHz Mercury instrument regulated at 25 C, 1 H NMR spectra of the samp le were recorded every 1 to 2 minutes. As the proton signals for most of the molecule remains unchanged throughout the exchange process, no other standard was needed for determining the remaining concentration of 60 as it reacted to form the H/D exchange product 60 d 4 ([(COD)Rh(L2 d 4 )(PtCl) 2 ]Cl 3 ). The aromatic

PAGE 132

132 region of the spectra, which is uninterrupted by solvent signals, served as the standard for integration of the disappearing dpa methylene peak at 5.37 ppm. Data points were collected past four hal f lives. The same procedure was followed for a 2.3 mg sample of complex 60 Analogous procedures were followed for studies involving complexes 58 and 59 Electrochemical Experiments The concentration of the electrolyte for all electrochemistry experiment s w as 0.1 M. Each experiment w as performed in an H cell using either a glassy carbon (cyclic voltammetry) or a reticulated vitreous carbon (bulk electrolysis) working electrode, a Pt flag auxiliary electrode, and a Ag/Ag + reference electrode. The refer ence electrode was made by first fitting a Vycor tip to the bottom of a glass tube. The tube was then filled with a CH 3 CN solution of 0.1 M TBAT and 0.01 M Ag(NO 3 ) and a sil ver wire was placed in the solution. Bulk electrolysis of hexanal (0.148 mL, 300 mM ) was performed in dichloroethane (4 mL) in the presence of crude 50 (23.7 mg, 9.43 mM) with 0.1 M TBAT as the electrolyte. The potential was fixed at 1.4 V versus NHE, and 60 L samples were removed after 20, 40, 60, 80, 100, and 280 C of charge had pass ed. Pentane was observed as a product by gas chromatography with heptane being utilized as an internal standard for quantification. IR Studies IR spectra for the Pd complexes were recorded for the products after purification. All reactions involving Cu(OT f) 2 Cu(NO 3 ) 2 CoCl 2 and Zn(NO 3 ) 2 were conducted in ambient atmosphere, and no purification steps were taken prior to collection of the IR spectra. In each case the metal reagent and ligand were dissolved in separate

PAGE 133

133 solutions in methanol or acetonitrile The metal reagent solution was then added dropwise to the stirring ligand solution and allowed to stir for around 30 minutes before the solvent was removed and the IR spectrum was recorded for the solid product. EPR Studies CW X band (9.62 GHz) measurem ents were recorded at 20 K in frozen solution. The methanol used in these studies was dried over 3 molecular sieves. DMSO was purchased from Fisher and used without further purification. Deionized water was also used without further purification. Sam ples of ligands bpy0, dpa, L2', L1, and L2 with varying ratios of Cu(OTf) 2 were prepared in both methanol (1.0 mM) and in 50:50 DMSO/H 2 O (1.4 mM) from appropriate stock solutions of the starting materials. Isolated Rh/Cu complexes 65 and 66 were dissolved in methanol (1.0 mM) while Pd/Cu and Pt/Cu samples 67 69 were dissolved in 50:50 DMSO/H 2 O (1.4 mM). The Pd/Cu and Pt/Cu complexes and 70 were prepared by reaction of complexes [ 46 ]PF 6 or [ 44 ]PF 6 with 1 equiv of Cu(OTf) 2 in 50:50 DMSO/H 2 O followed by appropriate dilutions to give a 1.44 mM solutions. X ray Crystallography Structure Determination All of t he structure s w ere solved using SHELXTL6.1 followed by full matrix least squares refinement. 134 A nisotropic thermal parameters were employed to refine all non H atoms. T he H atoms were calculated in idealized positions and then ref ined riding on their respective parent carbon atoms. [(L2'') 2 Co( Cl) 2 CoCl 2 ] (64) X Ray intensity data were recorded at 100 K on a Bruker DUO diffractometer using MoKa radiation (l = 0.71073 ) and an APEXII CCD area detector. The asymmetric unit cons ists of complex 64 and an acetonitrile solvent molecule. During the final refinement cycle 875 parameters were refined using 6985

PAGE 134

134 reflections (of which 5728 were observed with I > 2 (I)) yielding R 1 wR 2 and S (goodness of fit) values of 2.60%, 5.61% and 1.039, respectively. M inimiz ation of the wR 2 function was carried out using F 2 rather than F values. The R 1 function was not minimized, but was calculated to provide a reference to the conventional R value. trans [Cu(Cl) 2 (L3) 2 ] ( 72 ). X Ray intensity data were recorded at 100 K on a Bruker SMART diffractometer using MoKa radiation (l = 0.71073 ) and an APEXII CCD area detector. The asymmetric unit consists of complex 72 and two dis ordered MeOH molecules. As the solvent molecules could not be modeled properly, the solvent disorder area was calculated in the program SQUEEZE, a part of the PLATON package of crystallographic software, and its contribution to the overall intensity data was removed. During the final refinement cycle 218 parameters were refined using 3923 R 1 wR 2 and S (goodness of fit) values of 3.62%, 8.80% and 1.018, respectively. [Cu(Cl)(L3) 2 ]Cl ( 73 ). X Ray intensity data were recorded at 100 K on a Bruker DUO diffractometer using MoKa radiation (l = 0.71073 ) and an APEXII CCD area detector. During the final refinement cycle 353 parameters were refined using 6451 reflections (of which 5102 were ob served with I > 2 (I)) yielding R 1 wR 2 and S (goodness of fit) values of 3.56%, 9.52% and 0.983, respectively. trans [Co(Cl) 2 (L3) 2 ] ( 75 ). X Ray Intensity data were recorded at 100 K on a Bruker SMART diffractometer using MoKa radiation (l = 0.71073 ) and an APEXII CCD a rea detector. During the final refinement cycle 178 parameters were refined using R 1 wR 2 and S (goodness of fit) values of 3.01%, 5.44% and 0.926, respectively.

PAGE 135

135 APPENDIX X RAY CRY STAL STRUCTURE BOND LENGTHS AND ANGLES This Appendix contains tables of the bond lengths and angles of the five crystal structures described within Chapters 3 and 5 (Tables A 1 through A 8) The atom labels associated with complexes 72 73 and 75 can be found in Figures 5 4 through 5 7. Figure A 1 shows the atom labels for complex 64 The National Science Foundation and the University of Florida are acknowledged for funding of the purchase of the X ray equipment used. Figure A 1. Crystal structure d rawings of complex 64 with all atom labels

PAGE 136

136 Table A 1. Bond lengths () for complex 64 Co1 N2 2.098(2) C17 H17A 0.9500 C50 H50A 0.9500 Co1 N3 2.102(2) C18 C20 1.376(5) C51 C53 1.369(5) Co1 N1 2.124(2) C18 H18A 0.9500 C51 H51A 0.9500 Co1 N4 2.124(2) C19 C20 1.384(5) C52 C53 1.380(5) Co1 Cl2 2.4981(8) C19 H19A 0.9500 C52 H52A 0.9500 Co1 Cl1 2.5088(8) C20 H20A 0.9500 C53 H53A 0.9500 Co2 Cl4 2.2406(9) C21 C22 1.394(4) C54 C55 1.506(4) Co2 Cl3 2.2417(9) C22 C24 1.378(4) C54 H54A 0.9900 Co2 Cl2 2.3213(9) C22 H22A 0.9500 C54 H54B 0.9900 Co2 Cl1 2.3237(8) C23 C25 1.391(4) C55 C56 1.386(4) N1 C3 1.337(4) C23 H23A 0.9500 C55 C57 1.389(4) N1 C1 1.350(4) C24 C25 1.390(4) C56 C58 1.385(4) N2 C23 1.335(4) C24 H24A 0.950 0 C56 H56A 0.9500 N2 C21 1.359(4) C25 C26 1.508(4) C57 C59 1.382(4) N3 C43 1.340(3) C26 H26A 0.9900 C57 H57A 0.9500 N3 C41 1.353(3) C26 H26B 0.9900 C58 C60 1.384(4) N4 C63 1.337(3) C27 C28 1.509(4) C58 H58A 0.9500 N4 C61 1.356(3) C27 H27 A 0.9900 C59 C60 1.373(4) N5 C6 1.464(4) C27 H27B 0.9900 C59 H59A 0.9500 N5 C14 1.465(4) C28 C29 1.390(4) C60 H60A 0.9500 N5 C7 1.476(4) C28 C30 1.392(4) C61 C62 1.388(4) N6 C27 1.454(4) C29 C31 1.387(4) C62 C64 1.380(4) N6 C26 1.460(4) C29 H29A 0.9500 C62 H62A 0.9500 N6 C34 1.470(4) C30 C32 1.386(5) C63 C65 1.389(4) N7 C46 1.462(3) C30 H30A 0.9500 C63 H63A 0.9500 N7 C54 1.469(4) C31 C33 1.380(5) C64 C65 1.383(4) N7 C47 1.473(4) C31 H31A 0.9500 C64 H64A 0.9500 N8 C67 1.463(4) C32 C33 1.385(5) C65 C66 1.523(4) N8 C74 1.467(4) C32 H32A 0.9500 C66 H66A 0.9900 N8 C66 1.468(4) C33 H33A 0.9500 C66 H66B 0.9900 C1 C2 1.393(4) C34 C35 1.511(4) C67 C68 1.516(4) C1 C21 1.473(4) C34 H34A 0.9900 C67 H67A 0.9900 C 2 C4 1.375(4) C34 H34B 0.9900 C67 H67B 0.9900 C2 H2A 0.9500 C35 C36 1.386(4) C68 C69 1.388(4) C3 C5 1.386(4) C35 C37 1.388(4) C68 C70 1.388(4) C3 H3A 0.9500 C36 C38 1.390(4) C69 C71 1.389(4) C4 C5 1.380(4) C36 H36A 0.9500 C69 H69A 0.9500 C4 H4A 0.9500 C37 C39 1.381(4) C70 C72 1.388(4) C5 C6 1.502(4) C37 H37A 0.9500 C70 H70A 0.9500 C6 H6A 0.9900 C38 C40 1.380(4) C71 C73 1.381(4) C6 H6B 0.9900 C38 H38A 0.9500 C71 H71A 0.9500 C7 C8 1.510(4) C39 C40 1.381(4) C72 C73 1.377( 4) C7 H7A 0.9900 C39 H39A 0.9500 C72 H72A 0.9500 C7 H7B 0.9900 C40 H40A 0.9500 C73 H73A 0.9500 C8 C10 1.380(4) C41 C42 1.390(4) C74 C75 1.514(4)

PAGE 137

137 Table A 1. Continued. C8 C9 1.383(4) C41 C61 1.481(4) C74 H74A 0.9900 C9 C11 1.379(4) C42 C4 4 1.384(4) C74 H74B 0.9900 C9 H9A 0.9500 C42 H42A 0.9500 C75 C76 1.385(4) C10 C12 1.393(5) C43 C45 1.382(4) C75 C77 1.388(4) C10 H10A 0.9500 C43 H43A 0.9500 C76 C78 1.391(4) C11 C13 1.369(5) C44 C45 1.390(4) C76 H76A 0.9500 C11 H11A 0.9 500 C44 H44A 0.9500 C77 C79 1.383(4) C12 C13 1.367(5) C45 C46 1.504(4) C77 H77A 0.9500 C12 H12A 0.9500 C46 H46A 0.9900 C78 C80 1.382(4) C13 H13A 0.9500 C46 H46B 0.9900 C78 H78A 0.9500 C14 C15 1.504(4) C47 C48 1.504(4) C79 C80 1.379(5) C1 4 H14A 0.9900 C47 H47A 0.9900 C79 H79A 0.9500 C14 H14B 0.9900 C47 H47B 0.9900 C80 H80A 0.9500 C15 C17 1.393(4) C48 C50 1.380(4) N9 C81 1.123(5) C15 C16 1.397(4) C48 C49 1.392(4) C81 C82 1.448(6) C16 C18 1.377(5) C49 C51 1.380(4) C82 H82A 0.9800 C16 H16A 0.9500 C49 H49A 0.9500 C82 H82B 0.9800 C17 C19 1.397(5) C50 C52 1.385(4) C82 H82C 0.9800

PAGE 138

138 Table A 2 Bond angles () for complex 64 N2 Co1 N3 170.19(9) C67 N8 C66 112.8(2) N2 Co1 N1 77.74(10) C74 N8 C66 113.4(2) N3 Co1 N1 94.23(9) N1 C1 C2 120.6(3) N2 Co1 N4 97.27(9) N1 C1 C21 116.0(3) N3 Co1 N4 77.62(9) C2 C1 C21 123.4(3) N1 Co1 N4 94.87(8) C4 C2 C1 119.2(3) N2 Co1 Cl2 95.34(7) C4 C2 H2A 120.4 N3 Co1 Cl2 92.98(6) C1 C2 H2A 120.4 N1 Co1 Cl2 172.30 (7) N1 C3 C5 124.3(3) N4 Co1 Cl2 89.30(6) N1 C3 H3A 117.8 N2 Co1 Cl1 89.95(6) C5 C3 H3A 117.8 N3 Co1 Cl1 95.60(7) C2 C4 C5 121.1(3) N1 Co1 Cl1 89.19(6) C2 C4 H4A 119.5 N4 Co1 Cl1 172.32(7) C5 C4 H4A 119.5 Cl2 Co1 Cl1 87.42(3) C4 C5 C3 116.1(3) Cl4 C o2 Cl3 119.38(4) C4 C5 C6 123.3(3) Cl4 Co2 Cl2 115.52(3) C3 C5 C6 120.5(3) Cl3 Co2 Cl2 106.33(3) N5 C6 C5 110.9(2) Cl4 Co2 Cl1 106.80(3) N5 C6 H6A 109.5 Cl3 Co2 Cl1 110.03(3) C5 C6 H6A 109.5 Cl2 Co2 Cl1 96.29(3) N5 C6 H6B 109.5 Co2 Cl1 Co1 87.80(3) C 5 C6 H6B 109.5 Co2 Cl2 Co1 88.12(3) H6A C6 H6B 108.0 C3 N1 C1 118.7(2) N5 C7 C8 113.4(2) C3 N1 Co1 126.32(19) N5 C7 H7A 108.9 C1 N1 Co1 114.97(19) C8 C7 H7A 108.9 C23 N2 C21 119.0(2) N5 C7 H7B 108.9 C23 N2 Co1 125.2(2) C8 C7 H7B 108.9 C21 N2 Co1 115 .77(19) H7A C7 H7B 107.7 C43 N3 C41 118.7(2) C10 C8 C9 118.6(3) C43 N3 Co1 124.53(19) C10 C8 C7 122.0(3) C41 N3 Co1 115.94(18) C9 C8 C7 119.2(3) C63 N4 C61 118.6(2) C11 C9 C8 121.1(3) C63 N4 Co1 126.14(19) C11 C9 H9A 119.4 C61 N4 Co1 114.97(19) C8 C9 H9A 119.4 C6 N5 C14 111.6(2) C8 C10 C12 119.8(3) C6 N5 C7 110.9(2) C8 C10 H10A 120.1 C14 N5 C7 109.3(2) C12 C10 H10A 120.1 C27 N6 C26 112.3(2) C13 C11 C9 120.0(4) C27 N6 C34 108.5(2) C13 C11 H11A 120.0 C26 N6 C34 111.6(2) C9 C11 H11A 120.0 C46 N7 C 54 111.1(2) C13 C12 C10 120.7(3) C46 N7 C47 109.7(2) C13 C12 H12A 119.7 C54 N7 C47 109.6(2) C10 C12 H12A 119.7 C67 N8 C74 112.3(2) C12 C13 C11 119.7(3)

PAGE 139

139 Table A 2 Continued. C12 C13 H13A 120.1 C25 C26 H26B 109.3 C11 C13 H13A 120.1 H26A C26 H26B 107.9 N5 C14 C15 114.8(2) N6 C27 C28 115.9(3) N5 C14 H14A 108.6 N6 C27 H27A 108.3 C15 C14 H14A 108.6 C28 C27 H27A 108.3 N5 C14 H14B 108.6 N6 C27 H27B 108.3 C15 C14 H14B 108.6 C28 C27 H27B 108.3 H14A C14 H14B 107.5 H27A C27 H27B 107.4 C17 C15 C16 117.9(3) C29 C28 C30 118.5(3) C17 C15 C14 121.8(3) C29 C28 C27 122.3(3) C16 C15 C14 120.2(3) C30 C28 C27 119.0(3) C18 C16 C15 121.1(3) C31 C29 C28 120.6(3) C18 C16 H16A 119.5 C31 C29 H29A 119.7 C15 C16 H16A 119.5 C28 C29 H29A 119.7 C15 C17 C19 120.8(3) C32 C 30 C28 120.7(3) C15 C17 H17A 119.6 C32 C30 H30A 119.6 C19 C17 H17A 119.6 C28 C30 H30A 119.6 C20 C18 C16 120.7(4) C33 C31 C29 120.3(3) C20 C18 H18A 119.7 C33 C31 H31A 119.8 C16 C18 H18A 119.7 C29 C31 H31A 119.8 C20 C19 C17 119.9(4) C33 C32 C30 120.1(3 ) C20 C19 H19A 120.1 C33 C32 H32A 119.9 C17 C19 H19A 120.1 C30 C32 H32A 119.9 C18 C20 C19 119.6(4) C31 C33 C32 119.6(3) C18 C20 H20A 120.2 C31 C33 H33A 120.2 C19 C20 H20A 120.2 C32 C33 H33A 120.2 N2 C21 C22 120.4(3) N6 C34 C35 112.9(2) N2 C21 C1 115 .5(2) N6 C34 H34A 109.0 C22 C21 C1 124.1(3) C35 C34 H34A 109.0 C24 C22 C21 119.5(3) N6 C34 H34B 109.0 C24 C22 H22A 120.2 C35 C34 H34B 109.0 C21 C22 H22A 120.2 H34A C34 H34B 107.8 N2 C23 C25 123.9(3) C36 C35 C37 117.9(3) N2 C23 H23A 118.0 C36 C35 C34 121.4(3) C25 C23 H23A 118.0 C37 C35 C34 120.6(3) C22 C24 C25 120.5(3) C35 C36 C38 121.2(3) C22 C24 H24A 119.7 C35 C36 H36A 119.4 C25 C24 H24A 119.7 C38 C36 H36A 119.4 C24 C25 C23 116.5(3) C39 C37 C35 120.9(3) C24 C25 C26 123.4(3) C39 C37 H37A 119.5 C23 C25 C26 120.1(3) C35 C37 H37A 119.5 N6 C26 C25 111.7(2) C40 C38 C36 120.1(3) N6 C26 H26A 109.3 C40 C38 H38A 119.9 C25 C26 H26A 109.3 C36 C38 H38A 119.9 N6 C26 H26B 109.3 C40 C39 C37 120.7(3)

PAGE 140

140 Table A 2 Continued. C40 C39 H39A 119.6 C53 C52 H52A 1 19.9 C37 C39 H39A 119.6 C50 C52 H52A 119.9 C38 C40 C39 119.1(3) C51 C53 C52 119.9(3) C38 C40 H40A 120.5 C51 C53 H53A 120.0 C39 C40 H40A 120.5 C52 C53 H53A 120.0 N3 C41 C42 121.0(3) N7 C54 C55 113.9(2) N3 C41 C61 115.3(2) N7 C54 H54A 108.8 C42 C41 C6 1 123.7(3) C55 C54 H54A 108.8 C44 C42 C41 118.9(3) N7 C54 H54B 108.8 C44 C42 H42A 120.6 C55 C54 H54B 108.8 C41 C42 H42A 120.6 H54A C54 H54B 107.7 N3 C43 C45 124.2(3) C56 C55 C57 117.8(3) N3 C43 H43A 117.9 C56 C55 C54 121.6(3) C45 C43 H43A 117.9 C57 C55 C54 120.5(3) C42 C44 C45 120.8(3) C58 C56 C55 120.8(3) C42 C44 H44A 119.6 C58 C56 H56A 119.6 C45 C44 H44A 119.6 C55 C56 H56A 119.6 C43 C45 C44 116.3(3) C59 C57 C55 121.4(3) C43 C45 C46 121.0(3) C59 C57 H57A 119.3 C44 C45 C46 122.7(3) C55 C57 H57A 119.3 N7 C46 C45 112.2(2) C60 C58 C56 120.4(3) N7 C46 H46A 109.2 C60 C58 H58A 119.8 C45 C46 H46A 109.2 C56 C58 H58A 119.8 N7 C46 H46B 109.2 C60 C59 C57 120.2(3) C45 C46 H46B 109.2 C60 C59 H59A 119.9 H46A C46 H46B 107.9 C57 C59 H59A 119.9 N7 C47 C48 114.0(2) C59 C60 C58 119.3(3) N7 C47 H47A 108.8 C59 C60 H60A 120.3 C48 C47 H47A 108.8 C58 C60 H60A 120.3 N7 C47 H47B 108.8 N4 C61 C62 120.7(3) C48 C47 H47B 108.8 N4 C61 C41 115.3(2) H47A C47 H47B 107.7 C62 C61 C41 124.0(3) C50 C48 C49 118.0(3) C 64 C62 C61 119.4(3) C50 C48 C47 121.8(3) C64 C62 H62A 120.3 C49 C48 C47 120.0(3) C61 C62 H62A 120.3 C51 C49 C48 121.5(3) N4 C63 C65 124.2(3) C51 C49 H49A 119.3 N4 C63 H63A 117.9 C48 C49 H49A 119.3 C65 C63 H63A 117.9 C48 C50 C52 120.6(3) C62 C64 C65 1 20.6(3) C48 C50 H50A 119.7 C62 C64 H64A 119.7 C52 C50 H50A 119.7 C65 C64 H64A 119.7 C53 C51 C49 119.6(3) C64 C65 C63 116.4(3) C53 C51 H51A 120.2 C64 C65 C66 123.2(3) C49 C51 H51A 120.2 C63 C65 C66 120.4(3) C53 C52 C50 120.3(3) N8 C66 C65 116.5(2)

PAGE 141

141 Ta ble A 2 Continued. C53 C52 H52A 119.9 N8 C66 H66A 108.2 C50 C52 H52A 119.9 C65 C66 H66A 108.2 C51 C53 C52 119.9(3) N8 C66 H66B 108.2 C51 C53 H53A 120.0 C65 C66 H66B 108.2 C52 C53 H53A 120.0 H66A C66 H66B 107.3 N7 C54 C55 113.9(2) N8 C67 C68 113.8(2) N7 C54 H54A 108.8 N8 C67 H67A 108.8 C55 C54 H54A 108.8 C68 C67 H67A 108.8 N7 C54 H54B 108.8 N8 C67 H67B 108.8 C55 C54 H54B 108.8 C68 C67 H67B 108.8 H54A C54 H54B 107.7 H67A C67 H67B 107.7 C56 C55 C57 117.8(3) C69 C68 C70 118.3(3) C56 C55 C54 121.6( 3) C69 C68 C67 118.7(3) C57 C55 C54 120.5(3) C70 C68 C67 123.0(3) C58 C56 C55 120.8(3) C68 C69 C71 121.2(3) C58 C56 H56A 119.6 C68 C69 H69A 119.4 C55 C56 H56A 119.6 C71 C69 H69A 119.4 C59 C57 C55 121.4(3) C72 C70 C68 120.9(3) C59 C57 H57A 119.3 C72 C 70 H70A 119.6 C55 C57 H57A 119.3 C68 C70 H70A 119.6 C60 C58 C56 120.4(3) C73 C71 C69 119.6(3) C60 C58 H58A 119.8 C73 C71 H71A 120.2 C56 C58 H58A 119.8 C69 C71 H71A 120.2 C60 C59 C57 120.2(3) C73 C72 C70 120.0(3) C60 C59 H59A 119.9 C73 C72 H72A 120.0 C57 C59 H59A 119.9 C70 C72 H72A 120.0 C59 C60 C58 119.3(3) C72 C73 C71 120.1(3) C59 C60 H60A 120.3 C72 C73 H73A 119.9 C58 C60 H60A 120.3 C71 C73 H73A 119.9 N4 C61 C62 120.7(3) N8 C74 C75 113.7(2) N4 C61 C41 115.3(2) N8 C74 H74A 108.8 C62 C61 C41 124 .0(3) C75 C74 H74A 108.8 C64 C62 C61 119.4(3) N8 C74 H74B 108.8 C64 C62 H62A 120.3 C75 C74 H74B 108.8 C61 C62 H62A 120.3 H74A C74 H74B 107.7 N4 C63 C65 124.2(3) C76 C75 C77 118.0(3) N4 C63 H63A 117.9 C76 C75 C74 122.4(3) C65 C63 H63A 117.9 C77 C75 C7 4 119.6(3) C62 C64 C65 120.6(3) C75 C76 C78 120.7(3) C62 C64 H64A 119.7 C75 C76 H76A 119.6 C65 C64 H64A 119.7 C78 C76 H76A 119.6 C64 C65 C63 116.4(3) C79 C77 C75 121.4(3) C64 C65 C66 123.2(3) C79 C77 H77A 119.3 C63 C65 C66 120.4(3) C75 C77 H77A 119.3 N8 C66 C65 116.5(2) C80 C78 C76 120.6(3)

PAGE 142

142 Table A 2 Continued. C80 C78 H78A 119.7 N9 C81 C82 178.7(5) C76 C78 H78A 119.7 C81 C82 H82A 109.5 C80 C79 C77 120.3(3) C81 C82 H82B 109.5 C80 C79 H79A 119.9 H82A C82 H82B 109.5 C77 C79 H79A 119.9 C81 C82 H8 2C 109.5 C79 C80 C78 119.0(3) H82A C82 H82C 109.5 C79 C80 H80A 120.5 H82B C82 H82C 109.5 C78 C80 H80A 120.5 Table A 3 Bond lengths () for complex 72 Cu1 N2 2.0346(16) N3 C8 1.471(2) C8 H8B 0.9700 Cu1 N2#1 2.0346(16) N5 C9 1.337(3) C9 C10 1.386(3) Cu1 N1#1 2.0381(15) N5 C13 1.344(3) C13 C12 1.380(3) Cu1 N1 2.0382(15) C1 C2 1.380(3) C13 H13 0.9300 Cu1 Cl1 2.7029(5) C1 H1 0.9300 C12 C11 1.376(3) Cu1 Cl1#1 2.7030(5) C2 C3 1.385(3) C12 H12 0.9300 O1 C14 1.401(3) C2 H2 0.9300 C11 C10 1.383(3) O1 H1 0.8200 C3 C4 1.388(3) C11 H11 0.9300 O2 C15 1.383(3) C3 H3 0.9300 C10 H10 0.9300 O2 H2 0.8200 C4 C5 1.389(3) C14 H14A 0.9600 N1 C1 1.348(2) C4 H4 0.9300 C14 H14B 0.9600 N1 C5 1.354(2) C5 C6 1.457(3) C14 H14C 0.96 00 N2 N4 1.318(2) C6 C7 1.372(3) C15 H15A 0.9600 N2 C6 1.361(2) C7 H7 0.9300 C15 H15B 0.9600 N3 N4 1.344(2) C8 C9 1.504(3) C15 H15C 0.9600 N3 C7 1.345(2) C8 H8A 0.9700 Symmetry transformations us ed to generate equivalent atoms. #1 x+1, y +2, z+2

PAGE 143

143 Table A 4. Bond angles () for complex 72 N2 Cu1 N2#1 180.0 N1 C5 C6 113.53(16) N2 Cu1 N1#1 99.36(6) C4 C5 C6 123.91(18) N2#1 Cu1 N1#1 80.64(6) N2 C6 C7 107.69(17) N2 Cu1 N1 80.64(6) N2 C6 C5 117.91(17) N2#1 Cu1 N1 99.36(6) C7 C6 C5 134.41( 18) N1#1 Cu1 N1 180.000(1) N3 C7 C6 104.60(17) N2 Cu1 Cl1 89.04(5) N3 C7 H7 127.7 N2#1 Cu1 Cl1 90.96(5) C6 C7 H7 127.7 N1#1 Cu1 Cl1 87.48(5) N3 C8 C9 112.38(16) N1 Cu1 Cl1 92.52(5) N3 C8 H8A 109.1 N2 Cu1 Cl1#1 90.96(5) C9 C8 H8A 109.1 N2#1 Cu1 Cl1#1 89.04(5) N3 C8 H8B 109.1 N1#1 Cu1 Cl1#1 92.52(5) C9 C8 H8B 109.1 N1 Cu1 Cl1#1 87.48(5) H8A C8 H8B 107.9 Cl1 Cu1 Cl1#1 179.999(18) N5 C9 C10 123.26(18) C14 O1 H1 109.5 N5 C9 C8 116.76(17) C15 O2 H2 109.5 C10 C9 C8 119.91(18) C1 N1 C5 118.19(16) N5 C1 3 C12 124.2(2) C1 N1 Cu1 126.54(13) N5 C13 H13 117.9 C5 N1 Cu1 115.24(12) C12 C13 H13 117.9 N4 N2 C6 109.92(16) C11 C12 C13 118.2(2) N4 N2 Cu1 137.40(13) C11 C12 H12 120.9 C6 N2 Cu1 112.68(12) C13 C12 H12 120.9 N4 N3 C7 111.87(16) C12 C11 C10 119.0(2 ) N4 N3 C8 119.81(16) C12 C11 H11 120.5 C7 N3 C8 128.31(17) C10 C11 H11 120.5 N2 N4 N3 105.92(15) C11 C10 C9 118.8(2) C9 N5 C13 116.54(18) C11 C10 H10 120.6 N1 C1 C2 122.19(18) C9 C10 H10 120.6 N1 C1 H1 118.9 O1 C14 H14A 109.5 C2 C1 H1 118.9 O1 C14 H14B 109.5 C1 C2 C3 119.47(19) H14A C14 H14B 109.5 C1 C2 H2 120.3 O1 C14 H14C 109.5 C3 C2 H2 120.3 H14A C14 H14C 109.5 C2 C3 C4 119.09(19) H14B C14 H14C 109.5 C2 C3 H3 120.5 O2 C15 H15A 109.5 C4 C3 H3 120.5 O2 C15 H15B 109.5 C3 C4 C5 118.48(19) H15A C15 H15B 109.5 C3 C4 H4 120.8 O2 C15 H15C 109.5 C5 C4 H4 120.8 H15A C15 H15C 109.5 N1 C5 C4 122.56(18) H15B C15 H15C 109.5 Symmetry transformations us ed to generate equivalent atoms. #1 x+1, y+2, z+2

PAGE 144

144 Table A 5. Bond lengths () for complex 73 C u1 N10 2.0247(17) C1 C2 1.383(3) C14 C15 1.384(3) Cu1 N5 2.0378(18) C1 H1 0.9500 C14 H14 0.9500 Cu1 N9 2.0435(18) C2 C3 1.384(3) C15 C16 1.374(4) Cu1 N4 2.0443(18) C2 H2 0.9500 C15 H15 0.9500 Cu1 Cl2 2.4872(6) C3 C4 1.390(3) C16 C17 1.39 4(4) N1 C9 1.343(3) C3 H3 0.9500 C16 H16 0.9500 N1 C13 1.348(3) C4 C5 1.387(3) C17 C18 1.386(3) N2 N3 1.347(2) C4 H4 0.9500 C17 H17 0.9500 N2 C7 1.350(3) C5 C6 1.461(3) C18 C19 1.528(3) N2 C8 1.456(3) C6 C7 1.376(3) C19 H19A 0.9900 N3 N4 1.316(2) C7 H7 0.9500 C19 H19B 0.9900 N4 C6 1.356(3) C8 C9 1.513(3) C20 C21 1.374(3) N5 C1 1.351(3) C8 H8A 0.9900 C20 H20 0.9500 N5 C5 1.357(3) C8 H8B 0.9900 C21 C22 1.458(3) N6 C18 1.329(3) C9 C10 1.354(3) C22 C23 1.394(3) N6 C14 1 .341(3) C10 C11 1.391(4) C23 C24 1.394(3) N7 C20 1.348(3) C10 H10 0.9500 C23 H23 0.9500 N7 N8 1.352(2) C11 C12 1.361(4) C24 C25 1.393(3) N7 C19 1.459(3) C11 H11 0.9500 C24 H24 0.9500 N8 N9 1.310(2) C12 C13 1.370(4) C25 C26 1.387(3) N9 C2 1 1.364(3) C12 H12 0.9500 C25 H25 0.9500 N10 C26 1.346(3) C13 H13 0.9500 C26 H26 0.9500 N10 C22 1.355(3)

PAGE 145

145 Table A 6. Bond angles () for complex 73 N10 Cu1 N5 173.77(7) N5 C5 C4 122.8(2) N10 Cu1 N9 80.53(7) N5 C5 C6 113.39(18) N5 Cu1 N9 9 9.18(7) C4 C5 C6 123.79(19) N10 Cu1 N4 98.61(7) N4 C6 C7 107.76(18) N5 Cu1 N4 80.36(7) N4 C6 C5 117.87(19) N9 Cu1 N4 167.96(7) C7 C6 C5 134.2(2) N10 Cu1 Cl2 93.98(5) N2 C7 C6 104.30(19) N5 Cu1 Cl2 92.24(5) N2 C7 H7 127.9 N9 Cu1 Cl2 95.20(5) C6 C7 H7 127.9 N4 Cu1 Cl2 96.84(5) N2 C8 C9 114.84(18) C9 N1 C13 116.7(2) N2 C8 H8A 108.6 N3 N2 C7 111.88(18) C9 C8 H8A 108.6 N3 N2 C8 118.55(18) N2 C8 H8B 108.6 C7 N2 C8 129.44(19) C9 C8 H8B 108.6 N4 N3 N2 105.73(17) H8A C8 H8B 107.5 N3 N4 C6 110.33(17) N1 C9 C10 124.0(2) N3 N4 Cu1 136.51(14) N1 C9 C8 113.3(2) C6 N4 Cu1 112.80(14) C10 C9 C8 122.7(2) C1 N5 C5 117.85(18) C9 C10 C11 118.0(2) C1 N5 Cu1 126.42(15) C9 C10 H10 121.0 C5 N5 Cu1 115.47(14) C11 C10 H10 121.0 C18 N6 C14 116.8(2) C12 C11 C10 119.5( 2) C20 N7 N8 111.84(17) C12 C11 H11 120.2 C20 N7 C19 128.50(18) C10 C11 H11 120.2 N8 N7 C19 119.29(17) C11 C12 C13 118.8(2) N9 N8 N7 105.70(16) C11 C12 H12 120.6 N8 N9 C21 110.43(17) C13 C12 H12 120.6 N8 N9 Cu1 136.35(13) N1 C13 C12 123.0(2) C21 N9 Cu1 112.42(13) N1 C13 H13 118.5 C26 N10 C22 118.69(18) C12 C13 H13 118.5 C26 N10 Cu1 125.33(14) N6 C14 C15 124.1(2) C22 N10 Cu1 115.94(14) N6 C14 H14 118.0 N5 C1 C2 122.3(2) C15 C14 H14 118.0 N5 C1 H1 118.9 C16 C15 C14 118.2(2) C2 C1 H1 118.9 C16 C15 H15 120.9 C1 C2 C3 119.6(2) C14 C15 H15 120.9 C1 C2 H2 120.2 C15 C16 C17 118.9(2) C3 C2 H2 120.2 C15 C16 H16 120.6 C2 C3 C4 118.9(2) C17 C16 H16 120.6 C2 C3 H3 120.5 C18 C17 C16 118.4(2) C4 C3 H3 120.5 C18 C17 H17 120.8 C5 C4 C3 118.6(2) C16 C17 H1 7 120.8 C5 C4 H4 120.7 N6 C18 C17 123.6(2) C3 C4 H4 120.7 N6 C18 C19 116.82(18)

PAGE 146

146 Table A 6 Continued. C17 C18 C19 119.6(2) N10 C22 C21 113.18(17) N7 C19 C18 111.89(18) C23 C22 C21 124.37(19) N7 C19 H19A 109.2 C22 C23 C24 118.51(19) C18 C19 H19A 109 .2 C22 C23 H23 120.7 N7 C19 H19B 109.2 C24 C23 H23 120.7 C18 C19 H19B 109.2 C25 C24 C23 119.01(19) H19A C19 H19B 107.9 C25 C24 H24 120.5 N7 C20 C21 104.51(18) C23 C24 H24 120.5 N7 C20 H20 127.7 C26 C25 C24 119.2(2) C21 C20 H20 127.7 C26 C25 H25 120.4 N9 C21 C20 107.52(18) C24 C25 H25 120.4 N9 C21 C22 117.77(18) N10 C26 C25 122.2(2) C20 C21 C22 134.46(19) N10 C26 H26 118.9 N10 C22 C23 122.35(19) C25 C26 H26 118.9

PAGE 147

14 7 Table A 7 Bond lengths () for complex 75 Co1 N2 2.1009(19) N2 C6 1.366(3) C 4 C5 1.384(4) Co1 N2#1 2.1009(19) N3 N4 1.353(3) C5 C6 1.466(4) Co1 N1#1 2.140(2) N4 C7 1.349(4) C6 C7 1.378(3) Co1 N1 2.140(2) N4 C8 1.462(3) C8 C9 1.520(5) Co1 Cl1#1 2.4505(10) N5 C9 1.322(5) C9 C10 1.399(4) Co1 Cl1 2.4506(10) N5 C13 1.345(4) C10 C11 1.386(5) N1 C1 1.342(4) C1 C2 1.386(4) C11 C12 1.375(5) N1 C5 1.363(3) C2 C3 1.388(3) C12 C13 1.388(4) N2 N3 1.315(3) C3 C4 1.390(4) Symmetry transformations us ed to generate equivalent atoms. #1 x, y, z+1 Table A 8 Bo nd angles () for complex 75 N2 Co1 N2#1 180.0 C7 N4 C8 130.1(2) N2 Co1 N1#1 103.06(8) N3 N4 C8 118.1(2) N2#1 Co1 N1#1 76.94(8) C9 N5 C13 117.6(3) N2 Co1 N1 76.94(8) N1 C1 C2 122.7(2) N2#1 Co1 N1 103.06(8) C1 C2 C3 119.0(3) N1#1 Co1 N1 180.0 C2 C3 C4 119.1(3) N2 Co1 Cl1#1 93.14(9) C5 C4 C3 118.8(2) N2#1 Co1 Cl1#1 86.86(9) N1 C5 C4 122.4(3) N1#1 Co1 Cl1#1 90.45(8) N1 C5 C6 113.1(2) N1 Co1 Cl1#1 89.55(8) C4 C5 C6 124.5(2) N2 Co1 Cl1 86.86(9) N2 C6 C7 107.4(2) N2#1 Co1 Cl1 93.14(9) N2 C6 C5 117.7(2 ) N1#1 Co1 Cl1 89.55(8) C7 C6 C5 134.8(3) N1 Co1 Cl1 90.45(8) N4 C7 C6 104.7(2) Cl1#1 Co1 Cl1 180.0 N4 C8 C9 113.2(3) C1 N1 C5 118.1(2) N5 C9 C10 123.4(3) C1 N1 Co1 125.49(17) N5 C9 C8 118.6(3) C5 N1 Co1 116.42(19) C10 C9 C8 118.0(4) N3 N2 C6 110.36 (19) C11 C10 C9 118.0(4) N3 N2 Co1 133.60(18) C12 C11 C10 119.5(3) C6 N2 Co1 114.87(16) C11 C12 C13 118.3(4) N2 N3 N4 105.8(2) N5 C13 C12 123.3(4) C7 N4 N3 111.7(2) Symmetry transformations us ed to generate equivalent atoms. #1 x, y, z+1

PAGE 148

148 LIST OF REFERENCES (1) Van Den Beuken, E. K.; Feringa, B. L. Tetrahedron 1998 54 12985 13011. (2) Adams, R. D.; Cotton, F. A., Eds. Catalysis by Di and Polynuclear Metal Cluster Complexes ; Wiley VCH: New York, 1998. (3) Braunstein, P.; Rose J. In Metal Clusters in Chemistry ; Braunstein, P., Oro, L. A., Raithby, P. R., Eds.; Wiley VCH: Weinheim, 1999; Vol. 2, pp 616 677. (4) Stephan, D. W. Coord. Chem. Rev. 1989 95 41 107. (5) Mendoza Espinosa, D.; Donnadieu, B.; Bertrand, G. Chem. -Asian J. 2011 6 1099 1103. (6) Wheatley, N.; Kalck, P. Chem. Rev. 1999 99 3379 3419. (7) Cooper, B. G.; Napoline, J. W.; Thomas, C. M. Catalysis Reviews: Science and Engineering 2012 54 1 40. (8) Ishii, Y.; Hidai, M. Catal. Today 2001 53 61. (9) West, N. M.; Labinger, J. A.; Bercaw, J. E. Organometallics 2011 30 2690 2700. (10) Jones, N. D.; James, B. R. Adv. Synth. Catal. 2002 344 1126 1134. (11) Hildebrandt, A.; Wetzold, N.; Ecorchard, P.; Walfort, B.; Ruffer, T.; Lang, H. Eur. J. Inorg. Chem. 2010 3615 3627. (12) Hussain, M. M.; Li, H. M.; Hussain, N.; Urena, M.; Carroll, P. J.; Walsh, P. J. J. Am. Chem. Soc. 2009 131 6516 6524. (13) Yang, Y.; McElwee White, L. Dalton Trans. 2004 2352 2356. (14) Zhang, N.; Mann, C. M.; Shapley, P. A. J. Am. Chem. Soc. 1988 110 6591 6592. (15) Kuiper, J. L.; Shapley, P. A. J. Organomet. Chem. 2007 692 1653 1660. (16) Shibasaki, M.; Sasai, H.; Arai, T.; Iida, T. Pure Appl. Chem. 1998 70 1027 1034. (17) Quirmbach, M.; Kless, A.; Holz, J.; Tararov, V.; Brner, A Tetrahedron: Asymmetry 1999 10 1803 1811. (18) Hidai, M.; Fukuoka, A.; Koyasu, Y.; Uchida, Y. J. Chem. Soc., Chem. Commun. 1984 0 516 517. (19) Hidai, M.; Fukuoka, A.; Koyasu, Y.; Uchida, Y. J. Mol. Catal. 1986 35 29 37. (20) Hidai, M.; Matsuzaka, H. Polyhedron 1988 7 2369 2374.

PAGE 149

149 (21) Choukroun, R.; Iraqi, A.; Gervais, D.; Daran, J. C.; Jeannin, Y. Organometallics 1987 6 1197 1201. (22) Rida, M. A.; Smith, A. K. Modern Coordination Chemistry 2002 154 162. (23) Rida, M. A.; Smith, A. K. J. Mol. C atal. A: Chem. 2003 202 87 95. (24) Kuwabara, J.; Takeuchi, D.; Osakada, K. Chem. Commun. 2006 3815 3817. (25) Bahuleyan, B. K.; Lee, K. J.; Lee, S. H.; Liu, Y.; Zhou, W.; Kim, I. Catal. Today 2011 164 80 87. (26) Wang, J.; Li, H.; Guo, N.; Li, L.; St ern, C. L.; Marks, T. J. Organometallics 2004 23 5112 5114. (27) Zhong, R.; Wang, Y. N.; Guo, X. Q.; Chen, Z. X.; Hou, X. F. Chem. Eur. J. 2011 17 11041 11051. (28) Zanardi, A.; Mata, J. A.; Peris, E. Chem. Eur. J. 2010 16 13109 13115. (29) Zanardi, A.; Mata, J. A.; Peris, E. Chem. Eur. J. 2010 16 10502 10506. (30) Zanardi, A.; Mata, J. A.; Peris, E. J. Am. Chem. Soc. 2009 131 14531 14537. (31) Gu, S.; Xu, D.; Chen, W. Dalton Trans. 2011 40 1576 1583. (32) Peng, J.; Kishi, Y. Org. Lett. 2011 14 86 89. (33) Wasilke, J. C.; Obrey, S. J.; Baker, R. T.; Bazan, G. C. Chem. Rev. 2005 105 1001 1020. (34) Organometallics 2008 27 3570 3576. (35) Petretto, G. L.; Rourke, J. P.; Maidich, L.; Stoccoro, S.; Cinellu, M. A.; Minghetti, G.; Clarkson, G. J.; Zucca, A. Organometallics 2012 31 2971 2977. (36) Inag aki, A.; Edure, S.; Yatsuda, S.; Akita, M. Chem. Commun. 2005 0 5468 5470. (37) Shibasaki, M.; Yamamoto, Y., Eds. Multimetallic Catalysts in Organic Synthesis Wiley VCH Weinheim, 2004. (38) Garland, M. Organometallics 1993 12 535 543. (39) Ho, J. H. H. ; Wagler, J.; Willis, A. C.; Messerle, B. A. Dalton Trans. 2011 40 11031 11042. (40) Gavrilova, A. L.; Bosnich, B. Chem. Rev. 2004 104 349 384.

PAGE 150

150 (41) Berg, K. E.; Tran, A.; Raymond, M. K.; Abrahamsson, M.; Wolny, J.; Redon, S.; Andersson, M.; Sun, L. C. ; Styring, S.; Hammarstrom, L.; Toftlund, H.; Akermark, B. Eur. J. Inorg. Chem. 2001 1019 1029. (42) Lin, Q. T.; Pei, L. M.; Xu, W. C.; Chao, H.; Ji, L. N. Inorg. Chem. Commun. 2012 16 104 106. (43) Goforth, S. K. unpublished results. (44) Correia, M. P h D Dissertation, University of Florida, 2011 (45) Suess, D. L. M.; Peters, J. C. Chem. Commun. 2010 46 6554 6556. (46) Suntharalingam, K.; White, A. J. P.; Vilar, R. Inorg. Chem. 2010 49 8371 8380. (47) Wang, N.; Lu, J. s.; McCormick, T. M.; Wang, S. Dalton Trans. 2012 41 5553 5561. (48) Ishii, Y.; Onaka, K. i.; Hirakawa, H.; Shiramizu, K. Chem. Commun. 2002 1150 1151. (49) Dehaen, G.; Eliseeva, S. V.; Verwilst, P.; Laurent, S.; Elst, L. V.; Muller, R. N.; Borggraeve, W. D.; Binnemans, K.; Parac Vo gt, T. N. Inorg. Chem. 2012 51 8775 8783. (50) Tovee, C. A.; Kilner, C. A.; Barrett, S. A.; Thomas, J. A.; Halcrow, M. A. Eur. J. Inorg. Chem. 2010 2010 1007 1012. (51) Dubs, C.; Yamamoto, T.; Inagaki, A.; Akita, M. Organometallics 2006 25 1344 1358. (52) Blasberg, F.; Bolte, M.; Lerner, H. W.; Wagner, M. Organometallics 2012 31 3213 3221. (53) Maggini, S. Coord. Chem. Rev. 2009 253 1793 1832. (54) Tsukada, N.; Ohnishi, N.; Aono, S.; Takahashi, F. Organometallics 2012 31 7336 7338. (55) Karshted t, D.; Bell, A. T.; Tilley, T. D. Organometallics 2003 22 2855 2861. (56) Moret, M. E.; Chen, P. Organometallics 2008 27 4903 4916. (57) Tsukada, N.; Tamura, O.; Inoue, Y. Organometallics 2002 21 2521 2528. (58) Son, K. s.; Pearson, D. M.; Jeon, S. J .; Waymouth, R. M. Eur. J. Inorg. Chem. 2011 2011 4256 4261.

PAGE 151

151 (59) Dubs, C.; Yamamoto, T.; Inagaki, A.; Akita, M. Organometallics 2006 25 1359 1367. (60) Dutta, B.; Adhikary, B.; Flrke, U.; Nag, K. Eur. J. Inorg. Chem. 2006 2006 4111 4122. (61) Araya J. C.; Gajardo, J.; Moya, S. A.; Aguirre, P.; Toupet, L.; Williams, J. A. G.; Escadeillas, M.; Le Bozec, H.; Guerchais, V. New J. Chem. 2010 34 21 24. (62) Lee, P. K.; Law, W. H. T.; Liu, H. W.; Lo, K. K. W. Inorg. Chem. 2011 50 8570 8579. (63) Zhang L.; Clark, R. J.; Zhu, L. Chem. Eur. J. 2008 14 2894 2903. (64) Tamamura, H.; Ojida, A.; Ogawa, T.; Tsutsumi, H.; Masuno, H.; Nakashima, H.; Yamamoto, N.; Hamachi, I.; Fujii, N. J. Med. Chem. 2006 49 3412 3415. (65) Ojida, A.; Inoue, M. a.; Mito oka, Y.; Hamachi, I. J. Am. Chem. Soc. 2003 125 10184 10185. (66) Ojida, A.; Inoue, M. a.; Mito oka, Y.; Tsutsumi, H.; Sada, K.; Hamachi, I. J. Am. Chem. Soc. 2006 128 2052 2058. (67) Takebayashi, S.; Ikeda, M.; Takeuchi, M.; Shinkai, S. Chem. Commun. 2004 420 421. (68) Takebayashi, S.; Shinkai, S.; Ikeda, M.; Takeuchi, M. Org. Biomol. Chem. 2008 6 493 499. (69) Kawahara, S. i.; Uchimaru, T. Eur. J. Inorg. Chem. 2001 2437 2442. (70) Goforth, S. K.; Walroth, R. C.; McElwee White, L. Inorg. Chem. 2013 52 5692 5701. (71) Dorta, R.; Rozenberg, H.; Shimon, L. J. W.; Milstein, D. Chem. Eur. J. 2003 9 5237 5249. (72) Bax, A.; Summers, M. F. J. Am. Chem. Soc. 1986 108 2093 2094. (73) Hurd, R. E. J. Magn. Reson. 1990 87 422 428. (74) Hadden, C. E. Magn. Reson. Chem. 2005 43 330 333. (75) Spartan '10 ; Wavefunction Inc:Irvine, CA. (76) Rybtchinski, B.; Konstantinovsky, L.; Shimon, L. J. W.; Vigalok, A.; Milstein, D. Chem. Eur. J. 2000 6 3287 3292.

PAGE 152

152 (77) Rybtchinski, B.; Cohen, R.; Ben David, Y.; Marti n, J. M. L.; Milstein, D. J. Am. Chem. Soc. 2003 125 11041 11050. (78) Nanthakumar, A.; Fox, S.; Murthy, N. N.; Karlin, K. D. J. Am. Chem. Soc. 1997 119 3898 3906. (79) Kooistra, T. M.; Hekking, K. F. W.; Knijnenburg, Q.; Bruin, B. d.; Budzelaar, P. H. M.; Gelder, R. d.; Smits, J. M. M.; Gal, A. W. Eur. J. Inorg. Chem. 2003 648 655. (80) Storr, T.; Sugai, Y.; Barta, C. A.; Mikata, Y.; Adam, M. J.; Yano, S.; Orvig, C. Inorg. Chem. 2005 44 2698 2705. (81) Gerasimova, T. P.; Katsyuba, S. A. Dalton Trans 2013 42 1787 1797. (82) Ibrahim, M. M. J. Mol. Struct. 2011 990 227 236. (83) Kim, M.; Mora, C.; Lee, Y. H.; Clegg, J. K.; Lindoy, L. F.; Min, K. S.; Thury, P.; Kim, Y. Inorg. Chem. Commun. 2010 13 1148 1151. (84) Niklas, N.; Alsfasser, R. Dalton Trans. 2006 3188 3199. (85) Huang, G. S.; Lai, J. K.; Ueng, C. H.; Su, C. C. Transition Met. Chem. (Dordrecht, Neth.) 2000 25 84 92. (86) Chetty, R.; Scott, K. Electrochim. Acta 2007 52 4073 4081. (87) Stone, C. Fuel Cells Bull. 2007 12 15. (88) Hoga rth, M. P., Ralph, T. R. Platinum Met. Rev. 2002 46 146 164. (89) Barragn, V. M.; Heinzel, A. J. Power Sources 2002 104 66 72. (90) Tang, H.; Wang, S.; Pan, M.; Jiang, S. P.; Ruan, Y. Electrochim. Acta 2007 52 3714 3718. (91) Leger, J. M. J. Appl. E lectrochem. 2001 31 767 771. (92) Beden, B.; Lamy, C.; Bewick, A.; Kunimatsu, K. J. Electroanal. Chem. 1981 121 343 347. (93) Tess, M. E.; Hill, P. L.; Torraca, K. E.; Kerr, M. E.; Abboud, K. A.; McElwee White, L. Inorg. Chem. 2000 39 3942 3944. (94) Matare, G.; Tess, M. E.; Abboud, K. A.; Yang, Y.; McElwee White, L. Organometallics 2002 21 711 716. (95) Yang, Y.; Abboud, K. A.; McElwee White, L. Dalton Trans. 2003 4288 4296.

PAGE 153

153 (96) Vigier, F., Rousseau, S., Coutanceau, C., Leger, J. M., Lamy, C. Top Catal. 2006 40 111 121. (97) Correia, M. C.; Moghieb, A.; Goforth, S. K.; McElwee White, L. ECS Transactions 2009 19 13 21. (98) Wasmus, S.; Vielstich, W. J. Appl. Electrochem. 1993 23 120 124. (99) Wang, H. S.; Wingender, C.; Baltruschat, H.; Lope z, M.; Reetz, M. T. J. Electroanal. Chem. 2001 509 163 169. (100) Roth, C.; Martz, N.; Hahn, F.; Leger, J. M.; Lamy, C.; Fuess, H. J. Electrochem. Soc. 2002 149 E433 E439. (101) Hamnett, A.; Weeks, S. A.; Kennedy, B. J.; Troughton, G.; Christensen, P. A. Ber. Bunsen Ges. Phys. Chem. 1990 94 1014 1020. (102) Watanabe, M.; Motoo, S. J. Electroanal. Chem. 1975 60 276 283. (103) Watanabe, M.; Motoo, S. J. Electroanal. Chem. 1975 60 267 273. (104) Orth, S. D.; Terry, M. R.; Abboud, K. A.; Dodson, B.; M cElwee White, L. Inorg. Chem. 1996 35 916 922. (105) Serra, D.; Correia, M. C.; McElwee White, L. Organometallics 2011 30 5568 5577. (106) Serra, D.; McElwee White, L. Inorg. Chim. Acta 2008 361 3237 3246. (107) Ohno, K.; Tsuji, J. Tetrahedron Lett. 1967 23 2173 2179. (108) Ohno, K.; Tsuji, J. J. Am. Chem. Soc. 1968 90 99 107. (109) Doughty, D. H.; Pignolet, L. H. J. Am. Chem. Soc. 1978 100 7083 7085. (110) Chaudhuri, P.; Hess, M.; Mller, J.; Hildenbrand, K.; Bill, E.; Weyhermller, T.; Wieghar dt, K. J. Am. Chem. Soc. 1999 121 9599 9610. (111) Minato, D.; Arimoto, H.; Nagasue, Y.; Demizu, Y.; Onomura, O. Tetrahedron 2008 64 6675 6683. (112) Hossain, M. M.; Shyu, S. G. Adv. Synth. Catal. 2010 352 3061 3068. (113) Silva, A. C.; Fernndez, T. L.; Carvalho, N. M. F.; Herbst, M. H.; Bordinho, J.; Jr, A. H.; Wardell, J. L.; Oestreicher, E. G.; Antunes, O. A. C. Applied Catalysis A: General 2007 317 154 160. (114) Fernandes, R. R.; Lasri, J.; Guedes da Silva, M. F. C.; da Silva, J. A. L.; Fras to da Silva, J. J. R.; Pombeiro, A. J. L. J. Mol. Catal. A: Chem. 2011 351 100 111.

PAGE 154

154 (115) Chan, S. I.; Chien, C. Y. C.; Yu, C. S. C.; Nagababu, P.; Maji, S.; Chen, P. P. Y. J. Catal. 2012 293 186 194. (116) Misono, A.; Uchida, Y.; Hidai, M.; Kuse, T. C hem. Commun. 1968 981. (117) Tso, C. C.; Cutler, A. R. Organometallics 1986 5 1834 1840. (118) Galamb, V.; Palyi, G.; Boese, R.; Schmid, G. Organometallics 1987 6 861 867. (119) Gates, R. A.; D'Agostino, M. F.; Perrier, R. E.; Sayer, B. G.; McGlinchey M. J. Organometallics 1987 6 1181 1184. (120) Kovacs, I.; Szalontai, G.; Ungvary, F. J. Organomet. Chem. 1996 524 115 123. (121) Beck, R.; Floerke, U.; Klein, H. F. Inorg. Chem. 2009 48 1416 1422. (122) Fordyce, W. A.; Pool, K. H.; Crosby, G. A. In org. Chem. 1982 21 1027 1030. (123) Downard, A. J.; Bond, A. M.; Clayton, A. J.; Hanton, L. R.; McMorran, D. A. Inorg. Chem. 1996 35 7684 7690. (124) Sugai, Y.; Fujii, S.; Fujimoto, T.; Yano, S.; Mikata, Y. Dalton Trans. 2007 0 3705 3709. (125) Nikla s, N.; Hampel, F.; Walter, O.; Liehr, G.; Alsfasser, R. Eur. J. Inorg. Chem. 2002 2002 1839 1847. (126) Pap, J. S.; Kripli, B.; Bors, I.; Bogth, D.; Giorgi, M.; Kaizer, J.; Speier, G. J. Inorg. Biochem. 2012 117 60 70. (127) Hartman, J. R.; Vachet, R. W.; Pearson, W.; Wheat, R. J.; Callahan, J. H. Inorg. Chim. Acta 2003 343 119 132. (128) Kadish, K. M.; Deng, Y.; Zaydoun, S.; Idrissi, M. S. J. Chem. Soc., Dalton Trans. 1990 0 2809 2815. (129) Kuang, G. C.; Michaels, H. A.; Simmons, J. T.; Clark, R. J.; Zhu, L. The Journal of Organic Chemistry 2010 75 6540 6548. (130) Guha, P. M.; Phan, H.; Kinyon, J. S.; Brotherton, W. S.; Sreenath, K.; Simmons, J. T.; Wang, Z.; Clark, R. J.; Dalal, N. S.; Shatruk, M.; Zhu, L. Inorg. Chem. 2012 51 3465 3477. (13 1) Bugarcic, Z. D.; Liehr, G.; van Eldik, R. J. Chem. Soc., Dalton Trans. 2002 0 951 956. (132) Pitteri, B.; Marangoni, G.; Cattalini, L.; Visentin, F.; Bertolasi, V.; Gilli, P. Polyhedron 2001 20 869 880.

PAGE 155

155 (133) Wirbser, J.; Vahrenkamp, H. Z. Naturfors ch., B: Chem. Sci. 1992 47 962 968. (134) SHELXTL (2008 ); Bruker AXS:Madison, W I.

PAGE 156

156 BIOGRAPHICAL SKETCH Sarah Kathryn Goforth was born in Columbus, GA in 1986 and soon a fter which her army family made moves to Washington D.C. and Fayetteville, NC I n 1993, they settled in the great small town of Greenwood, SC which Sarah considers to be her hometown. S he received her Bachelors of Science in c hemistry and m athematics from Furman University in 2008 While at Furman, she worked extensively as a labora tory teaching assistant, and she performed inorganic research in the laboratory of Dr. Noel Kane Maguire. Her research involved the synthesis of various Cr(III) diimine complexes and diimine ligand as well as the study of their interactions with DNA. Aft er graduating from Furman in 2008, Sarah moved to Gainesville, FL and began her Ph.D. studies at the University of Florida where she joined the research group of Dr. Lisa McElwee White. She performed research in the field of organometallic chemistry in th e synthesis and characterization of heterometallic complexes with intended applications as homogeneous catalysts. In 2013, Sarah graduated from the Univer sity of Florida with her Ph.D. i n chemistry. She then continued on to the University of Virginia to begin her postdoctoral research in the laboratory of Dr. Brent Gunnoe.