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ONO3- AND OCO3- TRIANIONIC PINCER AND PINCER TYPE LIGAND SYNTHESIS AND APPLICATION TO NEW SULFIDE TUNGSTEN COMPLEX

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ONO3- AND OCO3- TRIANIONIC PINCER AND PINCER TYPE LIGAND SYNTHESIS AND APPLICATION TO NEW SULFIDE TUNGSTEN COMPLEX
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Reinman, Christi E.
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Trianionic pincer ligands mark an important development in organometallic chemistry. Their relatively recent discovery has opened a number of possibilities related to their unique structure. The most notable advantage of these ligands is the catalytic ability and summa kinetic stability attributed to their rigid tridentate conformation. Two specific examples of trianionic pincer and pincer-type ligands were synthesized and new reactions involving these ligands were explored. An ONO3- trianionic pincer type ligand specific to the Veige group was synthesized according to existing methods and attempts were made to form several new metal complexes with IrCl3, FeCl3, and RuCl2(PPh3)3. However, none of these attempts produced successful results. An OCO3- pincer ligand was also synthesized and successfully formed a tungsten metal complex known as Sarkar's catalyst. This complex was used in a successful reaction with CS2, which led to a new complex with catalytic abilities. Upon heating, the formation of an addition sulfide complex through the loss of a CS fragment was detected. Analysis and characterization of these structures were performed via multidimensional NMR, IR, and mass spectroscopy. A crystal structure of the second sulfide complex was obtained via single crystal X-ray diffraction. The catalytic abilities of the sulfide complex prior to heating were explored through the catalyzed polymerization of norbornene. The resulting polymer was determined to be a highly cis-syndiotactic cyclic polynorbornene through 1H NMR and GPC analysis. ( en )
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Awarded Bachelor of Science, summa cum laude, on May 8, 2018. Major: Chemistry
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College or School: College of Liberal Arts and Sciences
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Advisor: Adam Veige. Advisor Department or School: Department of Chemistry

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University of Florida
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Copyright Christi E. Reinman. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

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1 ONO 3 AND OCO 3 TRIANIONIC PINCER AND PINCER TYPE LIGAND SYNTHESIS AND APPLICATION TO NEW SULFIDE TUNGSTEN COMPLEX By CHRISTI ERIN REINMAN UNIVERSITY OF FLORIDA 2018

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2 TABLE OF CONTENTS CHAPTER 1. INTRODUCTION 2. SYNTHESIS OF ONO 3 TRIANIONIC PINCER TYPE LIGAND 3. SYNTHESIS OF OCO 3 TRIANIONIC LIGAND AND COMPLEX 4. REACTION OF OCO 3 TUNGSTEN COMPLEX WITH CS 2 5. POLYMERIZATION OF NORBORNENE 6. CONCLUSION 7. ACKNOWLEDGEMENTS APPENDIX A. SUPPORTING INFORMATION FOR CHAPTER 2 B. SUPPORTING INFORMATION FOR CHAPTER 3 C. SUPP ORTING INFORMATION FOR CHAPTER 4 D. SUPP ORTING INFORMATION FOR CHAPTER 5 REFERENCES

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3 LIST OF ABBREVIATIONS Bn Benzyl BOC tert butyloxycarbonyl DMF Dimethylformamide CDCl 3 Deuterated chloroform Equiv Equivalent Et Ethyl GPC Gel permeation chromatography HMBC Heteronuclear multiple bond coherence HSQC H eteronuclear single quantum correlation i Pr Isopropyl IR Infrared Me Methyl MeOD Deuterated Methanol m g Milligram min Minute mL Milliliter mmol Millimol M n Number average molecular weight M w Weight average molecular weight NBS N Bromosuccinimide NMR Nuclear Magnetic Resonance OCO 3 Trianionic donor ligand with two oxygen donor atoms and one central carbon donor atom. For this thesis, [ t BuOCO] 3 or di tert butyl terphenyl dioxide ONO 3 Trianionic donor ligand with two oxyg en donor atoms and one central nitrogen donor atom. For this thesis, [pyr ONO] 3 or 6,6' (1H pyrrole 2 ,5 diyl)bis(2 (tert butyl)phenoxide ) Ph Phenyl ppm Part(s) per million pyr pyrrole t Bu t ert butyl THF Tetrahydrofuran

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4 ABSTRACT Trianionic pincer ligands mark an important development in organometallic chemistry. Their relatively recent discovery has opened a number of possibilities related to their unique structure. The most notable advantage of these ligands is the catalytic abil ity and high kinetic stability attributed to their rigid tridentate conformation. Two specific examples of trianionic pincer and pincer type ligands were synthesized and new reactions involving these ligands were explored. An ONO 3 trianionic pincer type l igand specific to the Veige group was synthesized according to existing methods and attempts were made to form several new metal complexes with IrCl 3 FeCl 3 and RuCl 2 (PPh 3 ) 3 However, none of these attempts produced successful results. An OCO 3 pincer lig and was also synthesized and successfully formed a tungsten metal 2 which led to a new complex with catalytic abilities. Upon heating, the formation of an addition s ulfide complex through the loss of a CS fragment was detected Analysis and characterization of these structures were performed via multidimensional NMR, IR, and mass spectroscopy. A crystal structure of the second sulfide complex was obtained via single c rystal X ray diffraction. The catalytic abilities of the sulfide complex prior to heating were explored through the catalyzed polymerization of norbornene. The resulting polymer was determined to be a highly cis syndiotactic cyclic polynorbornene through 1 H NMR and GPC analysis.

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5 CHAPTER 1 INTRODUCTION The advancement and evolution of modern organometallic chemistry is largely influenced by the design of new ligands that manipulate the electronic and geometric structures of transition metal complexes. 1 Am ong the numerous variations of ligands, one of weighted significance is the pincer ligand. First appearing in the literature by Moulton and Shaw in 1976, 2 the pincer ligand is broadly defined as a ligand containing three donor atoms bound to adjacent copla nar sites in the meridional plane. 3 Specific examples of these structures are referred to with the three donor atoms in their corresponding order such that the central donor atom takes the middle position in the name. For example, t he pincer ligand in the complex depicted in Figure 1 is referred to as a PCP pincer ligand. Ligands containing a heteroatom in the central position of 3 Figure 1. Iridium complex supported by monoanionic PCP pincer ligand. 4 There are a number of advantages related to pincer ligands. Most p incer ligands hold a rigid conformation that provides structural control of the coordination sphere by retaining the donor groups in a predictable arrangement. 5 This rigidity makes these str uctures ideal for asymmetric catalysis because the prevention of rotation in the wingtip groups allows specific substituents to be directed into the active site of the catalyst. Due to these same structural

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6 reasons, pincer ligands which involve tridentate coordination, allow the stable binding of ligands which otherwise might be labile. For example, groups such as an aryl or a pyridine which would easily be lost as monodentate ligands are able to form stable complexes, especially if bound to the central do nor atom. 5 The strong binding of pincer ligands to metal centers causes a further advantage of forming highly stable complexes that do not decompose until after being heated above 100 C which is especially helpful in catalytic reactions performed at high temperatures 5 A major factor in this kinetic stability arrangement. A special type of pincer ligand, the trianionic pincer ligand, contains three anionic donors. This ligand was reported in th e literature near the turn of the century, such as a n NNN 3 by Shrock in 1996 6 7 even though trianionic to 2007 8 Previously, pincer and pincer type ligands had been limited to complexes involving metal ions in low oxidation states. However, with the emergence of multi anionic pincer ligands with electronically stabilizing properties such as the trianionic one previously mentioned, applications involving metal ions in high oxidation states have begun to be explored. 3 One application of trianionic pincer and pincer type ligands is the possible improvement of tungsten catalyzed alkyne cross metathesis. 9 This chemical process can be limited by the cycloaddition energy barrier associated with it, and thus improvements are possible if this energy barrier is able to be minimized. One method of achieving this outcome was explored by Jia and Lin whose theoretical calculations showed that a locked T shaped geometry of ancillary ligands would lower the relative transition state barrier by ~24 kcal/mol. 10 The rigid tridentate structure of trianionic pincer ligands helps to achieve this outcome by locking the supporting anionic

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7 donors in the desired T shaped geometry thus lowering the required activation energy and providing easier access for the alkyne. 9 This thesis focuses on two specific examples of trianionic pincer and pincer type ligands ONO 3 and OCO 3 and their application to several reactions. Both ligands were originally s ynthesized and studied in the Veige laboratory for various applications, and this thesis expands upon this research According to preceding literature, 3 OCO 3 complexes have successfully been formed with a variety of different transition metals including titanium, zirconium, tantalum, chromium, and molybdenum The research specific to this thesis focuses on OCO 3 tungsten complexes. ONO 3 ligands have also formed complexes with transition metals such as titanium, tantalum, and tungsten, to name a few. 3 This thesis explores attempts to expand the selection of transition metal complexes made with the specific ONO 3 ligand studied in the Veige group.

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8 CHAPTER 2 SYNTHESIS OF ONO 3 TRIANIONIC PINCER TYPE LIGAND Results and Discussion The first compound that was synthesized was a pyrrolide centered ONO 3 trianionic pincer type ligand ( 2 2). This ligand was synthesized through a series of steps according to the literature 9 and analysis was performed via 1 H NMR ( Figures A 1, A 2 ). Synthes is began with a coupling reaction using a palladium catalyst to form compound 2 1, followed by the deprotect ion of the compound to produce 2 2 ( Figure 3 1 ) Percent yield s for the reactions involved ( included in the experimental syntheses below ) were lower than those found in the literature, but not by more than 11%. 1 H NMR spectral assignments were consistent with literature reports ( Figure A 2 ) 9 Figure 3 1. Synthesis of [pyr ONO]Me 2 (2 1) and [pyr ONO]H 3 ( 2 2) Legend: (i) 10% Pd(PPh 3 ) 4 8 Na 2 CO 3 3 KCl, toluene, EtOH, and H 2 O, HCl/dioxane; (ii) KOt Bu, [HSCH 2 CH 2 NHMe 2 ]Cl, and DMF, HCl. Follo wing the synthesis of compound 2 2, several attempts were made to utilize it in the form ation of new and unexplored metal complexes. According to literature, compound 2 2 had previously been combined with TiCl 4 and ZrBn 4 to successfully synthesize new titanium and zirconium metal complexes. 11 Using a similar method as described in the literature, attempts 2 1 2 2

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9 were made to pr oduce new complexes th rough the reaction of compound 2 2 with IrCl 3 FeCl 3 and RuCl 2 (PPh 3 ) 3 The results were analyzed via 1 H NMR and 31 P NMR to monitor any changes in structure, however none of these attempts produced new stable complexes ( Figures A 3 through A 6) Factors such as the addition of heat or a base in the form of lutidine were explored without success. When combining 2 2 with Ir Cl 3 for instance, the on ly change detected via NMR was the deuteration of the backbone of the pyrrole in the liga nd, as seen in the disappearance of one of the resonance peaks ( Figure A 3 ). The c ombination with FeCl 3 produced data that was equally inconclusive. The RuCl 2 (PPh 3 ) 3 and 2 2 mixture was analyzed by 1 H NMR and 31 P NMR. The mixture was heated for 12 hr at 60 C in an attempt to induce change, but none occurred ( Figure A 5 ). Synthesis of 2,5 bis(3 (tert butyl) 2 methoxyphenyl) 1H pyrrole, [pyr ONO]Me 2 ( 2 1). Inside a nitrogen filled glove box, a 50 mL toluene solution was prepared containing 3.799 g (2.3 equiv ) (3 ( tert butyl ) 2 methoxyphenyl)boronic acid, 0. 916 g (0.10 equiv ) tetrakis(triphenylphosphine) palladium(0), 6.679 g (7.9 equiv ) Na 2 CO 3 1. 773 g (3 equiv ) KCl, and 2.579 g (1 equiv ) tert butyl 2,5 dibromo 1H pyrrole 1 carboxylate The reaction flask was then secured with a Liebig condenser and Y adapter before it was removed from the glove box and attached to an argon Schlenk line. Under argon counter pressure, 50 mL of degassed ethanol water (2:1) solution was added to the reaction flask. The mixtur e was heated at 96 C with stirring for about 20 h during which the solution changed in color from yellow to an orange red After being allowed to cool, all volatiles were removed from the reaction mixture under reduced pressure. The oily residue that remained was dissolved in CH 2 Cl 2 and washed with water and brine. The organic layer was then dried with MgSO 4 and after gravity filtration the solvent was removed under reduced pressure. 20 mL of hexanes was added to the residue to precipitate a

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10 white so lid and t he mixture was stirred for 0.5 h before filtering off the white solid. Volatiles of the collected filtrate w as removed u nder vacuum to yield an orange oil containing the BOC protected pyrrole. The BOC protecting group was removed by stirring the r esidue with 10 mL of 4 M HCl in 1,4 dioxane at 45 C for 18 h. The solvent of the resulting solution was removed under reduced pressure. The residue was then dissolved in CH 2 Cl 2 washed with a saturated solution of Na 2 CO 3 and then washed again with water. The organic layer was dried with MgSO 4 before removing the solvent under reduced pressure. The resulting purple oily residue was dissolved in minimal 2 propanol (5 mL). T he product, 2,5 bis(3 ( tert butyl ) 2 methoxyphenyl) 1H pyrrole, precipitated upon coo ling the solution. ( Yield = 0. 971 g, 36.2 %). Synthesis of 6,6' (1H pyrrole 2,5 diyl)bis(2 (tert butyl)phenol), [pyr ONO]H 3 ( 2 2). Inside a nitrogen filled glove box, a 250 mL two neck flask with a stir bar condenser, and Y adapter was charged with 0.842g 2 (diethylamin o)ethanethiol hydrochloride ( 2.4 equiv) and 1.199g NaOtBu ( 5.0 equiv). The apparatus was removed from the glovebox, then attached to a Schlenk line and cooled with an ice wa ter bath. Anhydrous DMF (10 mL) which had also been cooled in an ice water bath was added to the reaction flask. Following 5 min of stirring the reaction mixture was allowed to warm to room temperature. After stirring for additional 15 min, 0.971g of 2,5 bis(3 ( tert butyl ) 2 ethoxyphenyl ) 1H pyrrole (1.0 equiv) was added under counter argon flow, and the reaction mixture was refluxed for 3 h. The reaction mixture was allowed to cool to ambient temperature and then placed in an ice water bath. Under counter argon flow, the mixture was neutralized by acidifying with 1 M HCl and then was diluted with water (25 mL). The aqueous phase was extracted with ethyl acetate (3 x 25 mL) then t he combined organic extracts were w ashed with water (3 x 10 mL) and s aturated brine solution (10 mL) and then dried

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11 over MgSO 4 A ll volatil es were removed under vacuum resulting in a brown oil Recrystallization in cold pentane produced a beige powder (Yield = 0.3 93 g, 42.85 %). Procedure for attempted synthesis of iridium complex Inside a nitrogen filled glove box a J Young NMR tube was charged with 0. 0 15g of [pyr ONO]H 3 (1 equiv) and deuterated methanol ( MeOD ) and frozen at 35 C. Then 0. 0 1232g IrCl 3 (1 equiv) was dissolved in MeOD and the two solutions were combined T wo drops of lutidine were added to act as a base and a precipitate formed After this, the precipitate was filtered off. Results were analyzed via 1 H NMR. No changes in the complex structure were detected. In a second attempt in the glove box, a J Young NMR tube was charged with 0.0 15g of [pyr ONO]H 3 (1 equiv) and CDCl 3 and frozen at 35 C. Then 0.0207g of Lithium bis(trimethylsilyl)amide (3 equiv) in CDCl 3 was added. The mixture was then taken out of the glove box where 0.01232g iridium (III) chloride hydrate was added. When this occurred, the reaction turned green for a couple seconds and then turned into a brown slurry. Procedure for attempted synthesis of iron complex Inside a nitrogen filled glove box, a J Young NMR tube was charged with 0.0 15g of [pyr ONO]H 3 (1 equiv) and THF. After being frozen at 35 C, 0.0207g of Lithium bis (trimethylsilyl)amide (3 equiv) in THF was added to make a green solution. Then, 0.0074 g of FeCl 3 (1 equiv) was added at 35 C making a dark purple solution. Procedure for attempted synthesis of ruthenium complex Inside a nitrogen filled glove box, a J Young NMR tube was charged with 0.01181g of [pyr ONO]H 3 (1 equiv) and THF and frozen at 35 C. 0.031 g RuCl 2 (PPh 3 ) 3 (1 equiv) was dissolved in THF and the two solutions were combined

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12 CHAPTER 3 SYNTHESIS OF OCO 3 TRIANIONIC LIGAND AND COMPLEX Results and Discussion Another focus of the trianionic pincer ligand research covered in this thesis involves OCO 3 ligand (3 4) synthesis and its application to forming a tungsten complex ( 3 6) with catalytic abilities. Synthesis of the OCO 3 ligand and its corresponding tungs ten complex catalyst was performed according to the literature. 12 The synthetic process was initiated with a bromination reaction using NBS to form complex 3 1 which was then given a protecting group to form 3 2 ( Figure s 3 1 B 1 ) This was followed with a palladium catalyzed coupling with 1,3 dibromobezene to form 3 3. The desired OCO 3 ligand ( 3 4) was then obta ined after the deprotection of 3 3 ( Figure s 3 2 B 2 ). The trianionic ligand [ t BuOCO]H 3 (3 4) that was synthesized was utilized in the formatio n of a tungsten metal complex (3 6) with the compo 5) ( Figure s B 3 3 3 ). The complex 3 6 was determined to be successfully synthesized through the comparison of experimental 1 H NMR spectra to the literature ( Figures B 4 ). This tungsten complex was then used to explore reactions with CS 2 (See Chapter 4 ne polymerization (See Chapter 5 ). Figure 3 1. Synthesis o f 2 bromo 6 tert butylphenol (3 1) and 2 bromomethoxyphenol (3 2) 3 1 3 2

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13 Synthesis of 2 bromo 6 tert butylphenol (3 1) In a 500mL round bottom flask attached to an argon Schlenk line, 20.1 mL 2 tert butylphenol (1 equiv ) and 1.8 mL di isopropylamine (1 equiv ) were added to 150 mL oxygen free CH 2 Cl 2 under an argon counter pressure. In the fume hood, 23.304 g N bromosuccinimide (1 equiv ) was slowly added to the solution in four portions while stirrin g. After stirring overnight, the mixture was acidified through the addition of 1 M HCl. The organic phase of the reaction mixture was then washed two times with water and then dried with MgSO 4 The solvent was then evaporated under reduced pressure to obta in a yellow oil. (Yield = 27.3 g, 91.05%) Synthesis of 2 bromo methoxyphenol (3 2) In a 500 mL round bottom flask, 150 mL of dry DMF was added to 27.3g 2 bromo 6 tert butylphenol ( 3 1) (1 equiv ) while stirring. Then 24.67g K 2 CO 3 (1.5 equiv ) was added to produce a green solution. 11.154g MeI (1.5 equiv ) was directly added to the flask via syringe and then the reaction mixture was placed under argon and left to stir overnight. 100 mL water was added to the reaction mixture and which was then e xtracted with Et 2 O and washed with water and saturated brine solution. The organic layer was then dried with MgSO 4 before removing all volatiles under reduced pres sure, result ing in a yellow oil Crystallization in cold isopropanol formed white crystals of the product 2 bromomethoxyphenol (Yield 8.56g, 29.56%) Figure 3 2. Synthesis of [ t BuOCO](CH 3 ) 2 (3 3) and [ t BuOCO]H 3 ( 3 4) 3 2 3 3 3 4

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14 Synthesis o f [ t BuOCO] (C H 3 ) 2 ( 3 3 ) In a nitrogen filled glove box, 8.56g 2 bromomethoxyphenol ( 3 2) (1 equiv ) was dissolved in a minimal amount of THF and frozen in a cold well using liquid nitrogen 44.56 mL of tert butyl lithium (2.15 equiv ) was added dropwise in 15 mL increments while freezing the solution for 10 20 minutes in between each addition. After the addition was complete, the solution was allowed to warm to room temperature and stirred for 1 hour as a whitish yellow solution. 3.36g of solid ZnCl 2 (0.7 equiv ) was added before adding some additional THF to the mixture. The reaction mixture was allowed to stir for 30 min before 0.407g (Ph 3 P) 4 Pd (0.01 equiv ) was added. After the addition of 1.87 mL 1,3 dibromobezene (0.44 equiv ), whi ch resulted in the solution turning a darker color of yellow, the reaction mixture was taken out of the glove box with a condenser and y adapter securely attached to it and was refluxed overnight. The mixture was then quenched under argon with water and th e solvent was evaporated under reduced pressure. Water was then added before extracting with Et 2 O and then washing with water and concentrated brine solution. The organic layer was then dried with MgSO 4 and then all volatiles were removed under reduced pre ssure to leave a yellow oil. This was then crystallized with cold isopropa nol to obtain a white powder of the product. (Yield 2.816 g, 19.86%) Synthesis o f [ t BuOCO]H 3 ( 3 4) In a three neck flask with two septa attached 2.816g of [ t BuOCO](CH 3 ) 2 (3 3) (1 equiv ) was dissolved in 100mL of dry CH 2 Cl 2 under counter argon flow. After chilling in an ice bath, 3.32 mL BBr 3 (5 equiv ) was added via syringe through one septum. The reaction mixture was stirred for 5.5 hours and then was quenched with cold methanol. The solvent was then evaporated under reduced pressure. The residue was dissolved in hexanes, filtered, then an orange oil was removed from the bottom layer of the filtrate. The solvent was evaporated under

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15 reduced pressure, re dissolved in hexanes and co oled to induce precipitation. The precipitate was then collected as the product. (Yield not measured) Figure 3 3. Synthesis of [ t 3 ) 3 (O t Bu)(THF) (3 6) Synthesis of [ t 3 ) 3 (O t Bu)(THF) ( 3 6 ). In a nitrogen filled glove box 291.2 mg [ t BuOCO]H 3 ( 3 4) (1 equiv) in 1 mL THF was added to a glass vial and cooled to 35 C. In another vial 416 mg ( t BuO) 3 3 ) 3 ( 3 5 ) ( 1.14 equiv ) was dissolved in THF (1 mL) and added dropwise to the first solution while stirrin g. As th e dark brown solution was allowed to warm to room temperature a color change to dark yellow was observed, and the solution was allowed to stir for 30 additional min utes at room temperature. A dark tannish yellow tacky material was obtained after removing all volatiles under reduced pressure The solid was triturated with pentane three times before a final volume of 4 mL of pentane was added and the solution was cooled overnight at 35 C. The product formed as a tan precipitate (Yield = 1 74 mg, 29.3%) 3 4 3 5 3 6

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16 Figure 3 4. Synthesis of {[ t 3 ) 3 (O t Bu)}{Ph 3 PCH 3 } (3 7). Synthesis of {[ t 3 ) 3 (O t Bu)}{Ph 3 PCH 3 } (3 7 ). In a glass vial 174 mg [ t 3 ) 3 (O t Bu)(THF) ( 3 6 ) ( 0.225 mmol, 1 equiv ) was dissolved in 1 mL Et 2 O and then cooled to 35 C. 62.5 mg Ph 3 P=CH 2 (0. 225 mmol 1 equiv ) was dissolved in 0.5 mL Et 2 O and was then added to the cold solution of 3 6 The resulting mixture was warmed to 25 C and the solution brightened to a more yellow color T he solution was stirred for 45 min at room temperature and during that time a yellow solid precipitated out of solution The yellow product was collected by filtration and then washed with pentanes (3 x 1 mL). (Yield = 158 mg, 72.01% ) Figure 3 5. Synthesis of [ t 3 ) 3 (Et 2 O) (3 8). 3 6 3 7 3 7 3 8

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17 Synthesis of [ t 3 ) 3 (Et 2 O) (3 8 ). A glass vial was charged with 158 mg {[ t 3 ) 3 (O t Bu)}{Ph 3 PCH 3 } (3 7 ) (0.162 mmol 1 equiv ) and 1 mL Et 2 O and then cooled to 35 C. (0.162 mmol 1 equiv ) was dissolved in 0.5 mL Et 2 O and was then added dropwise to the cold suspension of 3 7 The resulting mixture was warmed to 25 C and stirred for 1 hour. While stirring, the solution changed in color from yellow to dark orange. P hos phonium triflate ([Ph 3 PCH 3 ][OSO 2 CF 3 ]) was formed as a white solid precipitat e which was removed via filtration. All volatiles were removed under reduced pressure and the resulting orange solid was triturated with pentane. C rystals were obtained by cooling a dilute diethyl ether solution of the product at 35 C for 3 d. (Yield = 67 mg, 58.97%)

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18 CHAPTER 4 REACTION OF OCO 3 TUNGSTEN COMPLEX WITH CS 2 Results and Discussion After the successful synthesis of 4 1 as seen in Chapter 3 several avenues in the application of this tungsten complex with regard to chemical reactions were explored. Following the precedent set by Gonsales with the successful reaction of 4 1 with CO 2 to form a new metal complex, 1 an attempt was made to form a new molecule through the reaction of 4 1 with CS 2 The experiment was performed on a small scale using similar methods to the previously successful reaction using CO 2 1 1 H NMR analysis on the reaction solution in reference to the initial reactants indicated the success of the reaction and the formation of a new metal complex ( Figure C 1 ). Figure 4 1. Synthesis of complexes 4 2 and 4 3. Initial a ttempts to isolate the resulting complex (4 2) were unsuccessful due to decomposition with the removal of solvents. However, subsequent experiments performed by Vineet Jak h ar rev ealed the crystal structure of 4 2 as seen in Figure 4 1 The reaction product was able to be characterized by multidimensio nal NMR ( Figures C 4, C 5 ) IR ( Figure C 3 ), and mass spectroscopy in THF ( Figures C 6, C 7 ). In the IR spectrum, unreacted CS 2 was detected along with a resonance that may be associated with the C=S bond, though its close CS 4 1 4 2 4 3

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19 approximation with other strong r esonances required further confi rmation ( Figure C 3 ) The W S bond was out of the spectral range and thus was not present in the obtained IR spectrum. Heating of 4 2 in solution for 18 h at 95C lead to the formation of a darker solution of 4 3 through the loss of a CS fragment ( Figure 4 1 ) Unlike 4 2, the 4 3 complex did not decompose with the rem oval of volatiles. Crystals of 4 3 were obtained from a concentrated Et 2 O solution and were used to obtain a crystal structure via single crystal X ra y diffraction ( Figure 4 2 ). Figure 4 2. Crystal structure of 4 3 Synthesis of Compound s 4 2 and 4 3 A J 3 ) 3 (THF) 2 ( 4 1) (0.100 g, 0.130 mmol, 1 equiv.) in C 6 D 6 After cooling the solution in the tube to 35C, CS 2 darkened in color to a black brown, was allowed to warm to room temperature At this point the compound 4 2 was characterized in situ a nd then was heated at 95C for 18 hours. All volatiles were removed in vacuo and the resulting residue was triturated with pentane (3 x 2 mL) and then taken up in a minimal amount of Et 2 O and filtered. The remaining volatiles of the filtrate w as then remov ed in vacuo. Single crystals were obtained from a concentrated Et 2 O solution of 4 3.

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20 CHAPTER 5 POLYMERIZATION OF NORBORNENE Results and Discussion The successful formation of a tungsten pincer complex with CS 2 that was the focus of Chapter 4 le d to It was noted in the study by Gonsales that the tungsten pincer complex incorporating CO 2 was the first complex to promote the ring expansion metathesis polymerization (REMP) of norbornene to give highly cis syndiotactic cyclic polynorbornene. 1 Due to the similarities to the compound synthesized by Gonsales, the initial complex formed with CS 2 prior to heating ( 5 1 ) was added to norbornene to determine its efficiency in acting as a polymerization c atalyst The result was analyzed via 1 H NMR at different intervals to monitor the reaction progression ( Figure D 1 ) Over time, the NMR resonances corresponding to the cis conformation ( 5.36 and 2.9 2 ppm) grew in intensity while those of the trans conformation ( 5.95 and 2.73 ppm ) decreased in relative intensity resulting in a 96% of the structure in the cis conformation ( Figure D 3 ) Thus, the synthesized catalyst was determined to give a highly cis syndiotactic polymer similar to the catalyst stud ied by Gonsales. 1 Gel Permeation Chromatography (GPC) was also used to analyze the resultant polynorbornene to provide evidence toward the cyclic nature of the polymer ( Figure D 4 ). Due to their smaller hydrodynamic radii, cyclic polymers have shorter elution times for a given molecular weight than their linear counterparts. 13 Comparison with literature results of cyclic polynorbornene confirmed the cyclic nature of the polymer. Catalysis of polymerization with complex 5 3 was not attempted and remains t o be explored in future research.

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21 Figure 5 1. Catalysis of the polymerization of norbornene by 5 1 Procedure for catalytic polymerization of Norbornene In a nitrogen filled glove box, a J Young NMR tube was charged with 19 mg of norbornen e (0.2018 mmol) dissolved in 1 mL of C 6 D 6 To this solution was added 2 drops of a 1 mL solution of 5 1 in C 6 D 6 as prepared in Chapter 4 with 30 mg and 1.1 equiv of CS 2 The mixture was monitored with 1 H NMR at intervals before leaving it overnight. The mixture was then dissolved in a small amount of toluene (3 mL) and added dropwise to a stirring methanol solution. The polymer was then recovered by filtration. 5 2 5 1

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22 CHAPTER 6 CONCLUSION The synthesis of an ONO 3 trianionic pincer type ligand specific to the Veige group was successfully achieved. Confirmation of the structure was made via 1 H NMR in reference to pre established literature. Following ligand synthesis, complexation with IrCl 3 FeCl 3 and RuCl 2 (PPh 3 ) 3 was attempted. The addition of heat or lutidine base were explored as contributing factors. Results were monitored via 1 H NMR and 31 P NMR, and all attempts were deemed unsuccessful. An OCO 3 trianionic pincer ligand and the associated tungsten metal complex the formation of a new complex through the reaction of CS 2 This complex was characterized by multidim ensional NMR, IR, and mass spectroscopy. Despite decomposition under reduced pressure, the sulfide complex became a new stable complex upon heating through the loss of a CS fragment. Single crystals of this more stable sulfide complex were obtained and use d for the determination of its crystal structure using single crystal X ray diffraction. The catalytic abilities of the original sulfide complex prior to heating were evaluated with its catalysis of the polymerization of norbornene. Through 1 H NMR and GPC analysis, the resultant polymer was determined to be a highly cis syndiotactic cyclic polynorbornene.

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23 ACKNOWLEDGMENTS I would like to thank Dr. Adam Veige for his patience and support and for allowing me to do research as an undergraduate in his research lab in the i norganic d ivision of the Department of Chemistry at the University of Florida. I would also like to acknowledge Dr. Soufiane Nadif for training me in the necessary lab techniques as well as for his guidance and support throughout my research. Finally, I would like to thank the members of the lab for providing a friendly and supportive environment, especially Stella Gonsales, Chris Beto, Chris Roland, Sud Venkatramani, and Vineet Jakhar.

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24 APPENDIX A SUPP ORTING INFORMATION FOR CHAPTER 2 Figure A 1. 1 H NMR spectrum of 2 2 in MeOD. Figure A 2. 1 H NMR spectrum of 2 2 in CDCl 3

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25 Figure A 3. 1 H NMR spectra of 2 2 before (bottom) and after (middle) adding IrCl 3 in MeOD, and the filtrate after lutidine was added (top). Figure A 4. 31 P NMR spectra of 2 2 with RuCl 2 (PPh 3 ) 3 in THF before (bottom) and after (top) heating for 12 hr at 60 C.

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26 Figure A 5. 1 H NMR spectra of 2 2 with RuCl 2 (PPh 3 ) 3 in THF before (bottom) and after (top) heating for 12 hr at 60 C. Figure A 6. 1 H NMR spectra of 2 2 with Ru Cl 2 (PPh 3 ) 3 in THF before (bottom) and after (top) adding lutidine base.

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27 APPENDIX B SUPPORTING INFORMATION FOR CHAPTER 3 Figure B 1. 1 H NMR spectrum of 2 bromomethoxyphenol ( 3 2). Figure B 2. 1 H NMR s pectrum of [tBuOCO]H 3 ( 3 4)

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28 Figure B 3. 1 H NMR s pectrum of 3 5. Figure B 4. 1 H NMR s pectrum of 6).

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29 APPENDIX C SUPPORTING INFORMATION FOR CHAPTER 4 Figure C 1. 1 H NMR spectrum of 4 2. Figure C 2. 1 H NMR spectrum of 4 3 upon heating 4 2.

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30 Figure C 2. 1 H NMR spectrum of the emergence of 4 3 after heating 4 2 (top) compared to before heating was induced (bottom). Figure C 3. IR spectrum of 4 2 with significant peaks labeled.

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31 Figure C 4. 1 H 13 C HSQC NMR spectrum of 4 2 Figure C 5. 1 H 13 C HMBC NMR spectrum of 4 2.

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32 Figure C 6. ESI MS Spectrum of 4 2. Figure C 7. ESI MS Spectrum of 4 2.

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33 APPENDIX D SUPPORTING INFORMATION FOR CHAPTER 5 Figure D 1. 1 H NMR spectra of polymerization of norbornene catalyzed by 5 1 over time. From bottom to top: catalyst 5 1 alone, poly merization reaction after 5 min, polymerization reaction after 45 min, and polymerization after being left overnight. Figure D 2. Labeled structure of polynorbornene

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34 Figure D 3 Labelled 1 H NMR spectrum of polymerized norbornene as catalyzed by 5 1 ( corresponding to structure in Figure D 2) Figure D 4 Gel Permeation Chromatography (GPC) data of norbornene polymerized by 5 1 a,b h,i c g d 1 e,f d 2

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35 REFERENCES 1 Gonsales, S. A.; Ghiviriga, I.; Abboud, K. A.; Veige, A. S. Carbon dioxide cleavage across a tungsten alkylidyne bearing a trianionic pincer type ligand. Dalton Trans ., 2016, 45, 15783. 2 Moulton C. J. & Shaw, B. L. Transition metal carbon bonds. Part XLII. Complexes of nickel, palladium, platinum, rhodium an iridium with tridentate ligands 2,6 bis (dit butylphosphino)methyl phenyl. J. Chem. Soc., Dalton Trans. 1976, 0, 1020 1024. 3 type metal complexes and catalysts. Chem. Soc. Rev ., 2014, 43, 6325. 4 Transition metal pincer complex. Wikipedia, April 14, 2018. 5 Peris, E & Crabtree, R. H. Key factors in pincer ligand design Chem. Soc. Rev ., 2018, 47, 1959. 6 Freundlich, J. S.; Schrock, R. R.; Davis, W. M. Synthetic and Mechanistic Investigations of Trimethylsilyl Multiple Bonds. J. Am. Chem. Soc ., 1996, 118, 3643 3655. 7 Freundlich, J. S.; Schrock, R. R.; Davis, W. M. Alkyl and Alkylidene Complexes of Tantalum That Contain a Triethylsilyl Organometallics 1996, 15, 2777 2783. 8 Koller, J.; Sarkar, S.; Abboud, K. A. ; Veige, A. S. Synthesis and Characterization of (2,6 i PrNCN)HfCl 2 and (3,5 MeNCN) 2 Hf 2 (where NCN = 2,6 New Trianionic Pincer Ligands Organometallics 2007, 26, 5438 5441. 9 Abboud, K. A.; Veige, A. S. Synthesis and Characterization of Tungsten Alkylidene and Alkylidyne Complexes Supported by a New Pyrrolide Centered Trianionic ONO 3 Pincer Type Ligand. Organometallics 2014, 33 (4), 836 839. 10 Zhu, J.; Jia, G.; Lin, Z. Theor etical Investigation of Alkyne Metathesis Catalyzed by W/Mo Alkylidyne Complexes. Organometallics, 11 proton storage within a pyrrolide pincer type ligand. Angew. Comm., 2015, 54 (50), 15138 15142. 12 Sarkar, S.; McGowan, K. P.; Kuppuswamy, S.; Ghiviriga, I.; Abboud, K. A.; Veige, A. S. An OCO 3 Trianionic Pincer Tungsten(VI) Alkylidyne: Rational Design of a Highly Active Alkyne Polymeriza tion Catalyst. J. Am. Chem. Soc ., 2012, 134 (10), 4509 4512. 13 Roland, C. D.; Li, H.; Abboud, K. A.; Wagener, K. B.; Veige, A. S. Cyclic polymers from alkynes. Nature 2016, 8, 791 796.

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36 Copyright Figures Used with Permission Figure 2 1 Modified and rep Ghiviriga, I.; Abboud, K. A.; Veige, A. S. Synthesis and Characterization of Tungsten Alkylidene and Alkylidyne Complexes Supported by a New Pyrrolide Centered Trianionic ONO 3 Pincer Type Ligand. Organometallics 2014, 33 (4), 836 839. Copyright 2014 American Chemical Society. Figure 3 3 Sarkar, S.; McGowan, K. P.; Kuppuswamy, S.; Ghiviriga, I.; Abboud, K. A.; Veige, A. S. An OCO 3 Trianionic Pincer Tu ngsten(VI) Alkylidyne: Rational Design of a Highly Active Alkyne Polymerization Catalyst. J. Am. Chem. Soc ., 2012, 134 (10), 4509 4512. Chemical Society. Figure 3 4 Sarkar, S.; McGowan, K. P.; Kuppuswamy, S.; Ghiviriga, I.; Abboud, K. A.; Veige, A. S. An OCO 3 Trianionic Pincer Tungsten(VI) Alkylidyne: Rational Design of a Highly Active Alkyne Polymerization Catalyst. J. Am. Chem. Soc ., 2012, 134 (10), 4509 4512. Chemical Society. Figure 3 5 Sarkar, S.; McGowan, K. P.; Kuppuswamy, S.; Ghiviriga, I.; Abboud, K. A.; Veige, A. S. An OCO 3 Trianionic Pincer Tungsten(VI) Alkylidyne: Rational Design of a Highly Active Alkyne P olymerization Catalyst. J. Am. Chem. Soc ., 2012, 134 (10), 4509 4512. Chemical Society. Figure 4 1 Used with permission from Soufianne Nadif. Figure 5 1 ; Kubo, T.; Flint, M. K. et all. Highly Tactic Cyclic Polynorbornene: Stereoselective Ring Expansion Metathesis Polymerization of Norbornene Catalyzed by a New Tethered Tungsten Alkylidene Catalyst. J. Am. Chem. Soc ., 2016, 138 (15), 4996 2016 American Chemical Society. Figure D 2 polyolefins via ring opening metathesis polymerization of ester functionalized cyclopentene and its copolymerization with cyclic comonomers. Polym. Chem., 2017, 8, 5924