Aluminum coordination compounds

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Aluminum coordination compounds
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xii, 143 leaves : ill. ; 29 cm.
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Browning, Kim E., 1965-
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Chemistry thesis Ph. D
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Thesis:
Thesis (Ph. D.)--University of Florida, 1995.
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Includes bibliographical references (leaves 138-142)
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by Kim E. Browning.
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Typescript.
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Vita.

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ALUMINUM COORDINATION COMPOUNDS


By

KIM E. BROWNING



















A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


1995














ACKNOWLEDGEMENTS


I would like to thank the following individuals for

assisting me with my research and the preparation of my

dissertation. Analytical Services of the UF Chemistry

Department prepared the FAB Mass Spectra. Dr. Khalil A.

Abboud performed the x-ray analysis on the structure discussed

in chapter 6. John West produced the Al-27 NMR spectra for

solutions and solid samples. I would also like to acknowledge

the encouragement, patience and assistance readily available

from Gus and Ruth Palenik.














TABLE OF CONTENTS





ACKNOWLEDGEMENTS.................................... .. ii

LIST OF TABLES ........................................ v

LIST OF FIGURES...................................... viii

ABSTRACT ............................................ xi

CHAPTERS

1 INTRODUCTION............................... 1
Potential Aluminum Health and
Environmental Issues............... 1
Coordination Chemistry of Aluminum.. 3
Aluminum Coordination Compounds ..... 5
Aluminum Complexes with a Nitrogen
Donor Atom......................... 6

2 SYNTHESIS AND CHARACTERIZATION OF
ALUMINUM COORDINATION COMPOUNDS........ 11
Aluminum as a Lewis Acid............. 11
Synthesis........................... 12
Solubility of Aluminum Coordination
Compounds......................... 20
Methods of Characterization of
Aluminum Complexes................. 21

3 CRYSTAL GROWTH TECHNIQUES UTILIZED TO
PRODUCE SINGLE CRYSTALS SUITABLE FOR
USE IN X-RAY DIFFRACTION STUDIES....... 27
Introduction........................ 27
Urea Decomposition ................... 27
Vapor Diffusion...................... 28
Gel Diffusion....................... 30
Base Strength....................... 33
Solvent System....................... 36
Aluminum Isopropoxide................ 38
Summary of Results................... 39


iii








4 SYNTHESIS, STRUCTURE AND ALUMINUM-27 NMR
STUDIES OF COMPLEXES WITH OXINE AND
2-METHYLOXINE.......................... 41
Introduction........................ 41
Experimental........................ 44
Discussion.......................... 48

5 ALUMINUM-27 NMR, INFRARED AND ELEMENTAL
ANALYSIS OF ALUMINUM COMPLEXES OF N,O
DONOR LIGANDS.......................... 67
Introduction........................ 67
Aluminum-27 NMR .. ...... .... ...... ... 67
Elemental Analysis.................... 82
Infrared Spectroscopy................ 84
Fast Atom Bombardment Mass
Spectrometry....................... 86
Conclusion.......................... 88

6 A PENTAGONAL BIPYRAMIDAL SODIUM COMPOUND:
SYNTHESIS AND CRYSTAL STRUCTURE........ 90
Introduction........................ 90
Experimental........................ 91
Discussion.......................... 94

7 SYNTHESIS AND STRUCTURE OF A COMPLEX
COMPOUND WITH PICOLINIC ACID AND
AMMONIUM NITRATE....................... 103
Introduction....................... .. 103
Experimental......................... 103
Discussion......................... .. 105

8 SYNTHESIS AND ABSOLUTE CONFIGURATION OF
SODIUM (+) TARTRATE MONOHYDRATE...... 115
Introduction....................... .. 115
Experimental......................... 115
Discussion......................... 117

9 CONCLUSION................................. 125
Characterization of Aluminum
Coordination Compounds............. 125
Crystal Growth Techniques............ 130
X-ray Diffraction Studies............ 133
Summary.............................. 137

REFERENCES ........................................ 138

BIOGRAPHICAL SKETCH............................... 143














LIST OF TABLES


Table Title Page

3-1 Vapor Diffusion Experimental Conditions
and Results............................. 30

3-2 Gel Diffusion Experimental Conditions
and Results............................. 32

3-3 Base Variation Experimental Conditions
and Results............................. 35

3-4 Experimental Conditions for Crystal
Growth in Various Solvents and Results.. 37

4-1 Crystallographic Data for I and II........ 49

4-2 Final Atomic Coordinates and Isotropic
Thermal Parameters for I................. 51

4-3 Hydrogen Atom Coordinates for I........... 52

4-4 Bond Lengths for I........................ 53

4-5 Bond Angles for I......................... 53

4-6 Anisotropic Temperature Parameters for
Non-Hydrogen Atoms for I................. 55

4-7 Final Atomic Coordinates and Isotropic
Thermal Parameters for II................. 58

4-8 Hydrogen Atom Coordinates for II.......... 59

4-9 Bond Lengths for II....................... 60

4-10 Bond Angles for II ........................ 60

4-11 Anisotropic Thermal Parameters for II ..... 62

5-1 Al-27 NMR Peak Data and Aluminum
Coordination............................ 68








5-2 Al-27 NMR Peak Data for Compounds III
through VII............................. 72

5-3 Al-27 NMR Data for Solutions Containing
0.30 M A13* and the Tabulated
Concentration of pza at pH 5............ 78

5-4 Elemental Analysis Data for Compounds
III through VII and Pure Tris Complexes
of the Ligands.......................... 83

5-5 FTIR Carbonyl Peak Data..................... 84

5-6 FABMS Peak Data........................... 87

6-1 Elemental Analysis of VIII.................. 92

6-2 Crystallographic Data for Compound VIII... 95

6-3 Final Atomic Coordinates and Isotropic
Thermal Parameters for the Non-Hydrogen
Atoms of Compound VIII.................... 97

6-4 Final Atomic Coordinates and Isotropic
Thermal Parameters for the Hydrogen
Atoms of Compound VIII.................... 98

6-5 Bond Lengths of all Atoms of Compound
VIII .................................... 98

6-6 Bond Angles for all Atoms of Compound
VIII .................................... 99

6-7 Anisotropic Thermal Parameters for the
Non-Hydrogen Atoms of Compound VIII..... 100

7-1 Crystallographic Data for IX ............... 106

7-2 Final Atomic Coordinates and Isotropic
Thermal Parameters for IX................ 109

7-3 Hydrogen Atom Coordinates and Isotropic
Thermal Parameters for IX................ 110

7-4 Bond Lengths for Non-Hydrogen Atoms in
IX ...................................... .. 110

7-5 Bond Lengths involving Hydrogen Atoms in
IX ...................................... .. 111

7-6 Bond Angles in IX........................... 111








7-7 Anisotropic Thermal Parameters for
Non-Hydrogen Atoms in IX................. 112

8-1 Crystallographic Data for X............... 118

8-2 Final Atomic Coordinates and Isotropic
Thermal Parameters for X................. 120

8-3 Bond Lengths and Angles for X............. 120

8-4 Anisotropic Thermal Parameters for
Non-Hydrogen Atoms in X.................. 122

8-5 Least Squares Planes Analysis of Square
Antiprismatic and Dodecahedral
Geometries for X.......................... 123


vii














LIST OF FIGURES


Figure Caption Page

1-1 Representation of Aluminum Complexes
with 3-Hydroxy-4-pyridinone and its
Derivatives............................. 5

1-2 ORTEP of the Aluminum Citrate Complex
and its A1304 Core....................... 6

1-3 9-Amino-l,2,3,4-tetrahydroacridine........ 7

1-4 Ligands with O-C-C-N Donor Group. Oxine;
2-Methyloxine; Picolinic acid;
6-Methylpicolinic acid; Pyrazinoic acid;
Hypoxanthine; Dipicolinic acid.......... 8

2-1 Representation of a Tris Complex between
Aluminum and a Bidentate Ligand......... 13

2-2 2-Methyloxine............................. 13

2-3 Oxine..................................... 14

2-4 Picolinic acid............................ 15

2-5 6-Methylpicolinic acid...................... 16

2-6 Pyrazinoic acid........................... 17

2-7 Hypoxanthine.............................. 18

2-8 Dipicolinic acid.......................... 19

4-1 Oxine; Methyloxine......................... 41

4-2 ORTEP Drawing of the Tris(oxinato)-
aluminum(III) without the Occluded
Acetonylacetone......................... 42

4-3 PLUTO Line Drawing of the A-Oxo-di(bis-
(2-methyloxinato)aluminum(III) Complex.. 43


viii








4-4 ORTEP Drawing of the Al(meox)3 Molecule
Showing the Atomic Numbering Scheme and
the Thermal Ellipsoids.................... 50

4-5 ORTEP of Al(ox)3 Molecule Showing the
Numbering Scheme and Thermal Ellipsoids. 57

4-6 Al-27 NMR Spectrum of the Solid Ia........ 63

4-7 Al-27 NMR Spectrum of the Solid IIa....... 65

4-8 Al-27 NMR Spectrum of Al(ox)3 in C2H5OH
Solution................................ 65

5-1 Ligands in Table 5-1. Iminodiacetic acid;
Nitrilotriacetic acid; N-(Hydroxyethyl)-
ethylenediaminetriacetic acid; Ethylene-
diaminetetraacetic acid; 1,2-Propylene
diaminetetraacetic acid; trans-1,2-
diaminocyclohexanetetraacetic acid;
Diethylenetriaminepentaacetic acid;
Pyromeconic acid; Maltol; 3-Hydroxy-2-
methyl-4-pyridinone; 3-Hydroxy-1,2-
dimethyl-4-pyridinone..................... 69

5-2 Al-27 NMR Spectra of III, Solid, in
d6-DMSO. ................................. 73

5-3 Al-27 NMR Spectra of IV, Solid, in d6-DMSO. 74

5-4 Al-27 NMR Spectra of V, Solid, in d6-DMSO.. 75

5-5 Al-27 NMR Spectra of VI, Solid, in dg-DMSO. 76

5-6 Al-27 NMR Spectra of VII, Solid, in
d6-DMSO. ................................. 77

5-7 Al-27 NMR Spectrum of an Aqueous
Solution Containing 0.30 M Al13 at pH 5.. 79

5-8 Al-27 NMR Spectrum of an Aqueous
Solution Containing 0.30 M Al3" and
0.30 M pza at pH 5 ...................... 79

5-9 Al-27 NMR Spectrum of an Aqueous
Solution Containing 0.30 M A13+ and
0.60 M pza at pH 5 ...................... 80


5-10 Al-27 NMR Spectrum of an Aqueous
Solution Containing 0.30 M Al3" and
0.90 M pza at pH 5 ...................... 80








6-1 Dipicolinic acid.......................... 90

6-2 ORTEP Representation of VIII.............. 96

7-1 ORTEP of Compound IX ...................... 107

7-2 Detail Showing Hydrogen Bonding in IX..... 108

8-1 ORTEP Drawing of X Showing the Atomic
Numbering Scheme ......................... 119

8-2 Sodium Ion Coordination in X, Showing
the Square Antiprismatic and
Dodecahedral Orientations............... 122














Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

ALUMINUM COORDINATION COMPOUNDS

By

Kim E. Browning

May 1995

Chairman: Gus J. Palenik, Ph. D.
Major Department: Chemistry

Long considered a harmless element, studies in recent

years have linked aluminum(III) with health and environmental

problems ranging from Alzheimer's Disease and Osteoporosis to

the deforestation and fish kills associated with acid rain.

The coordination chemistry of aluminum(III) must be further

understood to explain the mechanism by which aluminum(III) is

incorporated into the biosphere and what, if any, role it

might play in causing these disorders.

To date, the focus of aluminum(III) coordination

chemistry that has been conducted is with ligands containing

primarily oxygen donor atoms. Since many naturally occurring

compounds also contain nitrogen as a potential donor ligand,

the focus of this research has been to study the coordination

of aluminum(III) with naturally occurring compounds and

similar ligands that contain a potential N,O donor moiety.








The synthesis of aluminum(III) compounds with several N,O

donor ligands will be presented. Characterization by X-ray

crystallography was possible for some of the coordination

compounds despite efforts to grow suitable crystals by various

methods. X-ray diffraction techniques were used to examine

the similar environments of tris(oxinato)aluminum(III) and

tris(2-methyloxinato)aluminum(III). Furthermore, solution as

well as solid state Aluminum-27 Nuclear Magnetic Resonance

spectra are presented and compared for the synthesized

compounds. Aluminum-27 NMR spectroscopy provides information

about the coordination number and the type of atoms around the

metal center. Beyond X-ray crystallographic techniques, it is

probably the most useful for determining the environment

around a coordinated aluminum(III) ion. The shift downfield,

which is due primarily to the coordination number, varies when

different atoms are within the coordination sphere.

Therefore, a similar environment around the aluminum(III) ion

should produce a similar spectrum.

A discussion of the difficulties associated with aluminum

determination is included.


xii














CHAPTER 1

INTRODUCTION


Potential Aluminum Health and Environmental Issues


Traditionally considered to be a harmless element,

aluminum is widely used in the preparation of foodstuffs and

cosmetics. However, over the past couple of decades, aluminum

has been investigated with respect to a wide variety of

biological and environmental phenomena.

In the early 1980s, an extraordinarily high concentration

of aluminum was found, post mortem, as neurofibrillary tangles

and amyloid plaques in the brains of patients who had died of

Alzheimer's Disease.1 At first, aluminum was implicated as

the sole causative factor. To test this theory, several

studies were performed in various parts of the world to show

a causative relationship with respect to available aluminum

content in a drinking water and aluminum-containing products

such as antacids. The study on aluminum-containing products

reported no significant dose-response trend.2 The drinking

water studies showed a slight positive relationship for

aluminum content and a negative relationship for fluoride

content."3 However, in 1987, it was reported that the

precursor protein for the amyloid plaques was coded by a gene








2
on chromosome 21.4 It is rather an interesting occurrence

that chromosome 21 should be implicated in Alzheimer's

Disease. Down's Syndrome patients have an extra copy of

chromosome 21. Furthermore, autopsies have shown that

virtually all Down's patients that survive into their thirties

or forties get Alzheimer's Disease.4 Upon further research,

the metal was also detected in victims of Lou Gehrig's

Disease, also known as Amyotrophic Lateral Sclerosis, and

other neurological disorders such as epilepsy.s

Ordinarily, ingested aluminum is excreted rapidly during

normal kidney function.6 Individuals with kidney failure,

however, are subject to aluminum accumulation in several

tissues. First, aluminum is incorporated onto the bone

surface by the osteoblasts in the place of calcium, thereby

weakening the structure.7 In addition, in healthy bone, the

osteoclasts remove the top layers so that the bone can

continually be rebuilt. After the aluminum has accumulated on

the bone surfaces, the osteoclasts cannot remove it.7 As a

result the damage to the bone cannot be repaired and aluminum

adsorption continues to cover the bone surfaces. Once the

bone surfaces are saturated, the aluminum then begins to

concentrate in the brain.7 Patients of dialysis dementia,

characterized by speech difficulties, seizures and personality

changes, have markedly elevated levels of aluminum in their

brain tissues in amyloid plaques similar to those in

Alzheimer's Disease patients.809








3
Aluminum is the most abundant metallic element in the

earth's crust, but it is generally not available for uptake

into the biosphere. Under atmospheric conditions, elemental

aluminum can easily be oxidized to the trivalent aluminum ion,

that primarily exists as water insoluble mixed oxides and

silicates."1 When exposed to acidic conditions, such as in

acid rain, the oxides dissolve to yield a solution of

Al(H20) 63 ions and aluminum ions coordinated to naturally

occurring ligands."'12 As a mobile element, aluminum is

available for uptake by trees and aquatic organisms after it

has drained into lakes and rivers. As a result, increased

levels of aluminum have been implicated in the deforestation

and death of lakes commonly associated with acid rain.11,13

Because of the similar size and charges, aluminum could

compete with calcium, silicon and iron and interfere with

normal biological functions.3'14 In consideration of these

facts, an understanding of the reactivity and stability of

aluminum and its compounds warrants a thorough investigation.


Coordination Chemistry of Aluminum


In the presence of ligands other than water, the metal

ion can undergo exchange and loss of the water molecules.15

The factors controlling the coordination to a new ligand

include the formation of rings due to chelation, the geometry

around the metal center and the type of atom bonded to the

aluminum(III) ion.










A complex, formed by a ligand substituting for water,

would be less stable and less likely to form if there were too

much steric strain. Coordination numbers of four, five and

six are most commonly reported for Al(III) ." Too many ligands

around the metal center would be less stable due to crowding

caused by the relatively small metal ion radius, whereas too

few ligands would force Al(III) into a less favorable

geometry.

The formation of a five- or six-membered chelate ring

will provide stability to the complex due to the formation of

an unstrained ring structure. Organic rings of less than five

atoms are less stable because ring strain is created. If

chelation to a metal ion formed a small ring, the ligand would

be forced into a less stable configuration. The strain

occurring in the ligand is greater than if a larger ring were

formed. As a result, a less stable complex would be formed if

chelate rings are less than five-membered.

The donor atom bonded to the metal ion can affect the

stability of a complex. From equilibrium studies, a trend of

strength of complexation was determined as decreasing for the

ligands dicarboxylic acid, hydroxycarboxylic acid, carboxylic

acid and amino acid."6 Al(III), a relatively small ion with

a large positive charge, is a hard Lewis acid. Because oxygen

has a smaller size and larger negative charge, it has a

stronger attraction to the aluminum ion than nitrogen."0












O R =H Al(mpp)3

Al = CH3 Al(dpp)3

R = n-C6H1 Al (mhpp) 3

S H3 3



Figure 1-1. Representation of Aluminum Complexes with 3-
Hydroxy-4-pyridinone and its Derivatives. Nelson, Karpishin,
Rettig and Orvig, Inorganic Chemistry, 1988, 27, 1045-1051.

Aluminum Coordination Compounds

Complexes of Al(III) have been reported with many 0,0
donor ligands.17-23 For the derivatives of 3-hydroxy-4-

pyridinone, the complexes with the Al(III) ion, represented in

Figure 1-1, were synthesized by the addition of a base or

proton scavenger to a solution of ligand and Al(III)."7 By a

similar technique, complexes were also formed with maltol and

its derivatives, isomaltol, oxalic acid, tropolone and 2,4-

pentanedione.1822 Each of the compounds was characterized by

x-ray diffraction techniques as six coordinate tris chelates

with each ligand forming a five- or six-membered ring with the

central metal ion. The structure, shown in Figure 1-2, for

the complex of Al(III) with citric acid revealed a trinuclear

complex ion with each Al(III) in a distorted octahedral

environment.23
































Figure 1-2. ORTEP of the Aluminum Citrate Complex, left, and
its A1304 Core, right. Feng, Gurian, Healy and Barron,
Inorganic Chemistry, 1990, 29, 408-411.


Aluminum Complexes with a Nitrogen Donor Atom


There are many naturally occurring ligands and biological

molecules containing nitrogen as a potential donor atom. For

example, the pharmaceutical 9-amino-l, 2,3,4-tetrahydroacridine

(THA) pictured in Figure 1-3, has been used to alleviate

symptoms in Alzheimer's Disease patients. It has been

proposed that the aromatic ring is hydroxylated to yield a 0-

C-C-N donor group.24 Currently, the list of aluminum complexes

with a nitrogen as an electron donor is relatively short.25-43

From these studies, only seven coordination centers with N,0

donors have been confirmed by x-ray diffraction techniques.25-32

In an effort to further understand the behavior of Al(III),























NH2


Figure 1-3. 9-Amino-l,2,3,4-tetrahydroacridine (THA).

its complexation to ligands containing a potential donor

nitrogen has been investigated. These ligands, shown in

Figure 1-4, include oxine, 2-methyl-oxine, picolinic acid, 6-

methyl-picolinic acid, pyrazinoic acid, hypoxanthine and 2,6-

dipicolinic acid.

Oxine is structurally very similar to the suspected

metabolite of THA.24 The manner in which oxine reacts with the

aluminum ion could be important to the reason that THA is

effective in alleviating Alzheimer's symptoms. 2-Methyloxine

is different from oxine only by the presence of the methyl

group adjacent to the ring nitrogen. The steric interaction

that could occur due to the presence of the methyl group could

change the length and strength of the Al-N bond as well as

prevent the formation of the tris complex.
















(a)

HO






(c)

HO






(e)


OH


Figure 1-4. Ligands with O-C-C-N Donor Group.
a) Oxine; b) 2-Methyloxine; c) Picolinic acid;
d) 6-Methylpicolinic acid; e) Pyrazinoic acid;
f) Hypoxanthine; g) Dipicolinic acid








9

Picolinic acid is a naturally occurring compound that has

been found bound to aluminum in human breast milk."4 Picolinic

acid is structurally similar to oxine, but without the second

ring, the flexibility of the ligand would be greater. If an

aluminum and picolinic acid complex could be formed and

characterized, a comparison of Al-O and Al-N bond lengths

could be made with the oxine compounds. This analysis could

possibly determine if the nitrogen is coordinated to the

aluminum ion or held close to the ion simply because of its

location on the ring. 6-Methylpicolinic acid provides the

same potential comparisons for picolinic acid as 2-methyloxine

for oxine.

Pyrazinoic acid was chosen for its structural similarity

to picolinic acid. However, because of the second nitrogen

atom in the aromatic ring, the potential existed to have a

greater water solubility for an aluminum complex.

Hypoxanthine is formed in the animal body during the

breakdown of adenosine and nucleic acids. The two-ring

structure is similar to oxine; however, there are two notable

differences. First, there are three nitrogen atoms

substituted for ring carbons. Second, and probably more

important, is that one of the aromatic rings is a five

membered ring instead of six. As a result, the ring strain

should pull the nitrogen atom farther from the aluminum ion in

a coordination compound.








10
A naturally occurring ligand, 2,6-pyridinedicarboxylic

acid, has the potential to be an electron donor from the

nitrogen as well as the two carboxylate oxygens. This

molecule, also known by its common name dipicolinic acid, has

been reported in a variety of compounds as a tridentate

ligand.4s5i5 Because dipicolinic acid has the potential to

coordinate as a bidentate as well as a tridentate ligand,

there is more than one possible mode of coordination. If only

one of the carboxylate groups is deprotonated, then

dipicolinic acid should act as a bidentate ligand. In a

three-to-one ratio, the neutral tris complex could

theoretically be formed. Another type of complex could be

formed if both of the carboxylic acid groups on dipicolinic

acid were deprotonated. Were this to occur, dipicolinate

could act as a tridentate ligand by coordinating aluminum with

a nitrogen and both oxygen atoms.

The details of the investigation into the aluminum

complexes for these ligands are presented in the following

chapters. In addition, three compounds without aluminum were

inadvertently synthesized during this project. The structure

determinations for these compounds is also included.














CHAPTER 2

SYNTHESIS AND CHARACTERIZATION OF
ALUMINUM COORDINATION COMPOUNDS


Aluminum as a Lewis Acid


The only non-zero valence state available to aluminum is

a positive three. Since it can attain a positive charge, the

aluminum ion will readily accept electron pair donors and

function as a Lewis acid. The trivalent aluminum ion has a

rather small ionic radius of 0.50 A.10 As a result, the

aluminum ion with a relatively high positive charge coupled

with a small ionic radius can be classified as a hard Lewis

acid.

In an aqueous solution of an aluminum salt, the metal ion

will be surrounded by six water molecules, each of which

donates an electron pair to the positive central ion. For a

ligand to replace the water molecule and coordinate the metal

ion, the complex formed by the exchange should be more stable.

One possibility is for the electron donor atom to be a small

atom, such as oxygen and nitrogen, and also have a stronger

negative charge. An example would be a deprotonated hydroxyl

group or carboxylate oxygen. With a negative charge, each of

these ions would function as harder Lewis bases and more

readily replace the water molecule. The other possibility for

11








12

creating a more stable complex is by the formation of one or

more five- or six-membered rings by complexation of two or

more functional groups belonging to the same donor molecule.

Most nitrogen donor atoms occur as the amine functional

group, whether aromatic or aliphatic. In amines, the nitrogen

atoms are more likely to become positively charged than

negatively. As a result, even though a nitrogen atom can

coordinate to an aluminum ion, the electrostatic attraction

between the metal ion and an oxygen donor tends to be stronger

and, therefore, forms more stable complexes.


Synthesis


The general technique for the synthesis of an aluminum

complex involves the combination of a soluble aluminum salt,

the ligand and a base. When the ligand is deprotonated, a

negatively charged donor atom is created. If the anionic

part of the ligand is a harder Lewis base than water, it is

then capable of displacing the neutral water molecule. If the

ligand can only carry one negative charge and this process is

repeated two more times, a neutral aluminum species is formed.

Such a non-charged species, especially with a shell of

aromatic carbon and hydrogen atoms, will generally have a

relatively low water solubility. Therefore, after a certain

quantity of the complex is formed, it will begin to

precipitate. The solid can then be collected by filtration,

rinsed and dried. Depending upon solubility, the complex may






















Figure 2-1. Representation of a Tris Complex between Aluminum
and a Bidentate Ligand.


be dissolved in an appropriate solvent to be recrystallized.

The specific techniques used to synthesize the complexes

depend in part on the solubility and the acidity of the

particular ligand.

Materials

All materials and solvents used were reagent grade and

used as supplied by the manufacturer.

2-Methyloxine (meox)

Licrand reactivity. 8-Hydroxyquinaldine, represented here

as meox, is soluble in organic solvents such as ethanol and

dimethylsulfoxide (DMSO) but insoluble in water. With a pKa

of 10.1, meox is a rather weak acid that will require a

moderately strong base for deprotonation.

HO

Fu N CH3




Figure 2-2. 2-Methyloxine, meox.








14

Preparation of Al (meox) 3. CH3OH_-H,-2 (I). DMSO (39 mL) was

placed in a 200 mL round bottom flask which was set in a 900C

oil bath to warm. A12(S04)3-18 H20 (3.31 g, 10 mmole Al(H2O))63)

was added and dissolved by stirring. 2-Methyloxine (5.02 g,

32 mmole) was subsequently added to yield a dark amber

solution. The solution was neutralized slowly by the addition

of 0.5 mL portions of diethylamine (7.5 mL, 72 mmol). The

resulting opaque mixture was stirred and heated for an

additional 10 minutes and then cooled to room temperature. A

dark amber solution (30 mL) was obtained by filtration through

a fine glass frit. After two months, large brown crystalline

clumps formed which were then redissolved in 15 mL methanol

and covered to slowly recrystallize. In two months, small

brown needles of diffraction quality were separated from the

solution.

Oxine (ox)

Ligand reactivity. 8-Hydroxyquinoline, commonly referred

to as oxine, has a similar solubility to meox. However, it is

more acidic, with a pKa of 9.0, and therefore, will be easier

to deprotonate the hydroxyl group.


Figure 2-3. Oxine (ox).








15

Preparation of Al(ox) 3. CH30OH (II). To avoid the lengthy

recrystallization required with I, the synthetic scheme was

modified to exclude DMSO. Al(NO3)3-9H20 (0.181 g, 0.5 mmole)

was dissolved in 150 mL of H20. Oxine (0.220 g, 1.5 mmole)

was added as a solid and slowly dissolved in the acidic

aqueous solution to yield a pale yellow solution. The pH of

the mixture was slowly raised by dropwise additions of NaOH

until a very, thick yellow precipitate formed at pH = 5.2.

The solid was collected by filtration and recrystallized from

95% ethanol. Diffraction quality crystals were obtained by

recrystallization of the solid from the solution.

Picolinic Acid (pic)

Ligand reactivity. Picolinic acid is very soluble in

water and ethanol, but insoluble in organic solvents such as

ether. With a pKa of 5.4, it functions as a moderately weak

acid.


HO


0





Figure 2-4. Picolinic acid (pic).


Preparation of Al/pic complex (III). Al(NO3)- 9H20 (1.25

g, 3.33 mmole) was dissolved in 15 mL H20. In a separate

beaker, pic (1.23 g, 10.0 mmole) was dissolved in 20 mL H20.








16

The solutions were combined to give a clear, colorless

solution. NaHCO3 was added slowly as a solid until a thick,

white precipitate formed. The pH of the mixture measured 5.0.

The result was identical for a concentrated solution of NaOH.

The solid was collected by filtration through a glass frit,

washed thoroughly with water and dried for further analysis.

6-Methylpicolinic acid (mpic)

Ligand reactivity. 6-Methylpicolinic acid has a

solubility similar to picolinic acid. With a pKa of 5.8, it

is only a slightly weaker acid the picolinic acid.


HO









Figure 2-5. 6-Methylpicolinic acid (mpic).


Preparation of Al/mpic complex (IV). Al (NO3) 3"9H20 (1.24

g, 3.3 mmole) was dissolved in 15 mL H20. Mpic (1.37 g, 10.0

mmole) was dissolved in 20 mL H20 to produce a pale beige

solution. The solutions were combined to give a clear, almost

colorless solution. NaHC03 was slowly added as a solid until

a thick off-white precipitate formed. The pH of the resulting

solution was 6.0. The solid was collected by filtration

through a glass frit, washed thoroughly with H20 and dried for

further analysis.










Pyrazinoic acid (pza)

Ligand reactivity. Pyrazinoic acid is slightly soluble

in hot water and ethanol and insoluble in organic solvents.



HO







Figure 2-6. Pyrazinoic acid (pza).


Preparation of Al/pza complex (V). Pza (3.00 g, 24.2

mmole) was added to 100 mL H20 but did not dissolve. In a

separate beaker, Al(N03) 39H20 (3.02 g, 8.05 mmole) was

dissolved in 25 mL 95 % ethanol. The solutions were combined

and stirred to yield a 125 mL clear and colorless solution

with a white suspension. As NaHCO3 (2.03 g, 24.2 mmole) was

slowly added as a solid, the suspension disappeared and the

mixture became a clear pale pink solution. When all the

NaHCO3 had been added, the clear pink solution had a pH of

5.0. Additional NaHCO3 was added until a solid white

precipitate formed. The pH of the opaque mixture measured

7.5. The solid was collected by filtration through a medium

glass frit and washed thoroughly with water and hot ethanol.

The solid was dried in a desiccator for further analysis.










Hypoxanthine (hyp)
Ligand reactivity. Hypoxanthine is not appreciably

soluble in any solvent; however, it will react with acid or

basic solutions to dissolve in water. It is a very weak acid

with a pKa of 12.
HO


NNN



Figure 2-7. Hypoxanthine (hyp).

Preparation of Al/hyp complex (VI). Hyp (0.775 g, 5.69

mmole) was added to 80 mL of H20 with stirring and heated to

80C. This produced an opaque white solution in which the

ligand settled quickly as a fine intensely white powder when

not stirring. Al(NO3)3-9H2O (0.712 g, 1.90 mmole) was

dissolved in a separate 5 mL H20. The two solutions were

combined to yield a mixture of pH 4.0. The temperature was

maintained at 800C. NaHCO3 (0.482 g, 5.73 mmole) was slowly

added as a solid. After addition of the base was complete,

the pH of the mixture was 7.5. A large amount of white solid

was still visible but only some settled to the bottom when

stirring was stopped. A fluffy cream white solid remained

suspended above the bottom of the beaker. The temperature was

lowered to 600C and the mixture continued to heat for one

hour. Without stirring, only a small amount of white powder

settled. The unstirred solution carefully filtered through a








19
medium frit. The white powder on the bottom of the beaker was

discarded. The solid collected by filtration was washed

thoroughly with water and dried in a desiccator for further

analysis.

Dipicolinic acid (dipic)

Liqand reactivity. Dipicolinic acid is slightly soluble

in hot water or ethanol and insoluble in all other solvents.

It is a moderately strong acid with a pKa of 2.2 for its first

dissociation.



HO OH


0 0





Figure 2-8. Dipicolinic acid (dipic).

Preparation of Al/dipic (VII). Dipic (4.00 g, 24.0

mmole) was added with stirring to 100 mL of H20 at room

temperature. NaHCO3 (1.00 g, 11.9 mmole) was added as a solid

to partially neutralize the ligand. After the solution was

stirred for 20 minutes, the ligand dissolved to yield a clear,

colorless solution. Al(N03) 3.9H20 (2.99 g, 8.0 mmole) was

added as a solid to the solution. After ten minutes, the pH

measured 2.0 for the clear and colorless solution. Additional

NaHCO3 (3.02 g, 36.0 mmole) was added slowly to the mixture.








20

After addition of the NaHCO3 was complete, the clear,

colorless solution had a pH of 5.0. Within five minutes, the

solution started to cloud. Five minutes later, the mixture

consisted of an opaque white solid that would remain as a

fluffy white suspension when not stirring. The mixture was

allowed to stir at room temperature for three days. The solid

was collected by vacuum filtration through a course glass

frit, rinsed thoroughly with water followed by absolute

ethanol and then dried for further analysis.


Solubility of Aluminum Compounds


After a complex has been synthesized, it can be purified

by recrystallization. A pure compound would yield accurate

and useful information from elemental and spectral analysis.

In addition, with the growth of good quality crystals, the

structure can be determined by x-ray diffraction techniques.

Without the possibility of purifying the synthesized complex,

characterization becomes extremely difficult.

Of the seven compounds synthesized, all are insoluble in

water. Complexes I and II were sufficiently soluble in

ethanol or methanol to be recrystallized. It was determined

that the other compounds must not be the sodium salts of the

ligands. When synthesized, the sodium salts were found to be

very soluble in water. However, since the pure compounds

could not be produced by recrystallization, various crystal

growth techniques were employed to obtain pure compounds and








21
possibly good crystals. The discussion of crystal growth

techniques is presented in detail in Chapter 3.


Methods of Characterization of Aluminum Complexes


There are several techniques that can be utilized to

characterize an aluminum complex that has been synthesized.

These methods include elemental analysis, Infra-red, Al-27 NMR

and ICP emission spectroscopies, Fast Atom Bombardment Mass

Spectrometry (FABMS) and x-ray diffraction techniques. The

first three can be performed upon the insoluble compounds III

through VII. ICP emission spectroscopy, FABMS and x-ray

diffraction techniques require that the samples are soluble.

Elemental Analysis

Elemental analysis can be used to determine the

percentage of all of the elements in a compound. CHN, which

can be performed on solid samples, only determines the

percentages of carbon, hydrogen and nitrogen. From these

percentages, the ratios of the number of carbon to hydrogen to

nitrogen atoms present in the compound can be calculated.

Since hydrogen has a very low atomic weight, the percentages

and ratios for this element have a large relative error.

Therefore, the ratio of carbon atoms to nitrogen atoms

provides the most valid numerical data. Since each ligand has

a specific number of carbon and nitrogen atoms, the presence

of an organic solvent molecule or an ammonium ion in a

synthesized compound can easily be confirmed.








22
By determining the percent of carbon, hydrogen and

nitrogen present, the total percent of the other elements,

oxygen, aluminum and possibly sodium, can be calculated.

Since each ligand has a specific number of oxygen atoms, the

corresponding percentage of ligand oxygen can be calculated

and then subtracted to yield the percentage accounting for the

metal ion and the oxygen present as solvent molecules. The

oxygen associated with water can not be accurately determined

because of the uncertainty in the amount of hydrogen present.

In addition, because the substitution of a sodium and two

hydrogen atoms for an aluminum would only produce an error of

2 g/mole, is difficult to prove of disprove the presence of

aluminum, as opposed to sodium, based on elemental analysis

data.

Infra-red Spectroscopy

IR spectroscopy provides information about the strength,

and therefore the length, of a bond. The C=O group in a

carboxylic acid has a very strong stretch in the region 1760

to 1700 cm-1.52 If the acid is deprotonated to form a

carboxylate anion, the carbonyl bond loses some of its double

bond character due to the delocalization of the electron pair

over both of the carboxylate oxygen atoms. As a result, the

carbonyl bond strength decreases as the bond length increases.

The stretching frequency of a longer bond is slower such that

the stretching band shifts to a range of 1650 to 1550 cm-1.52

If a complex is formed involving the carboxylate group, the








23
bond length for the carbonyl group would probably be between

that for the acid and the anion. Therefore, the carbonyl

stretching frequency should lie between those of the unreacted

ligand and its sodium salt.53

Aluminum-27 NMR Spectroscopy

Al-27 NMR is a technique used to probe into the

environment of aluminum in its compounds. A peak will be

present for each different aluminum atom. The shift of the

peak is indicative of the geometry, symmetry and the type of

atoms surrounding the metal center.

Most of the research reported for Al-27 NMR refers to

exclusively oxygen atoms bonded to the aluminum and the shifts

are referenced relative to Al(H20)3". Most of the octahedral

A106 groups have shifts very near 0 ppm, whereas the

tetrahedral A104 groups are shifted to near 80 ppm.54 However,

for an aluminophosphate, the shift of 41 ppm was attributed to

the tetrahedral A104 group in the compound.55 Also, the Al-27

NMR shifts reported for the distorted octahedral environments

in tris complexes of 0,0 bidentate ligands range from 36 to 41

ppm.17 18 These shifts are in the same range as reported for

some tetrahedral aluminum centers. Not all of the studies on

coordination compounds have been performed on exclusively

oxygen environments. The shift due to the octahedral

environment in fluoroaluminates was reported to range from

+1.4 to -13.2 ppm.56 In addition, an Al-27 NMR study including

hexacoordinate aluminum complexes formed with








24
aminopolycarboxylic acids reported that the chemical shifts

range from 36.5 to 41.2 ppm.57 For one of the acids, EDTA, the

aluminum ion was determined by x-ray diffraction techniques to

be in a distorted octahedral environment in K[Al(EDTA)]*2H20

coordinated to two nitrogen atoms and four oxygen atoms.58

However, there have been a limited number of studies reported

Al-27 NMR for the A1N303 centers produced by the formation of

a tris complex with a N,O bidentate ligand. The shifts for

the four similar complexes range from 8.1 to 11.4 ppm.27 These

complexes contained an O-C-C-C-N group instead of the O-C-C-N

group present in each of the ligands in this study and had

coordination spheres fairly close to the ideal octahedron.

ICP Emission Spectroscopy

ICP emission spectroscopy depends upon the emission of

light at a specified wavelength after the aluminum ion has

been excited in the plasma. The concentration of aluminum can

be determined by comparing it to a calibration curve. If the

mass of the complex per volume is accurately known for the

test solution, then the molecular weight of the complex can be

determined. All of the emission lines for aluminum are

extremely weak and a rather high detection limit exists.

Therefore, not only is a solution required but it must be

relatively concentrated. This technique was not feasible to

employ due to the very low solubility of the synthesized

complexes.










Fast Atom Bombardment Mass Spectrometry

FABMS, a technique developed in the early 1980s, is used

to study the composition of a compound. The method has proven

useful for compounds of high molecular weight or low

volatility and for polar molecules.59 However, due to beam-

induced reduction or inefficient fragmentation, there is a

limit to its application.60 In FABMS, the sample is excited

by bombardment with high-energy atoms of either xenon or

argon, instead of the more traditional beam of high-energy

electrons.59 The charged molecules and fragments are then

separated by the use of a magnetic field. The data that can

be extracted include the molecular mass, or masses if the

sample is a mixture, and structural hints from the masses of

the fragments. Because of the low solubility of the samples,

the usefulness of this technique is limited.

X-ray Diffraction Techniques

Also known as x-ray crystallography, this method is used

to determine the location and type of each atom present in the

complex. The data required are collected by passing an x-ray

beam through a single crystal and measuring the intensity and

the angle of each diffracted beam relative to the incident

beam. The diffractions are caused by the electrons around

each atom scattering the x-ray beam. After preliminary

calculations, a test structure is proposed. The diffraction

pattern that would be produced by the test structure is








26
compared to the actual pattern and refinements are made to the

test structure until the best match is obtained.61

Since the x-ray beam is diffracted by each atom's

electrons, two atoms with the same number of electrons would

diffract the beam in almost the same manner. For example, an

aluminum ion and a sodium ion would be difficult, but not

impossible, to differentiate. The structure should refine

better with the correct atom.

The greatest disadvantage to x-ray diffraction techniques

is the requirement of a single crystal approximately 0.1 to

0.3 mm in each dimension. In the absence of a suitable

crystal, this technique cannot be employed to determine the

structure of a complex.














CHAPTER 3
CRYSTAL GROWTH TECHNIQUES UTILIZED TO PRODUCE SINGLE
CRYSTALS SUITABLE FOR USE IN X-RAY DIFFRACTION STUDIES


Introduction


In order to characterize a compound by x-ray

crystallography, a single good crystal approximately 0.2 mm in

a dimension is required.61 When a suitable solvent is

available, crystals can be grown by slow evaporation of a

saturated solution of the compound. If a complex is not

soluble, a variety of crystal growth techniques can be

employed.61 The concept used in many methods involves

controlling the rate of reaction so that suitable crystals are

produced as the compound is formed. In this study, the rate

of reaction depends upon the availability of the aluminum ion,

the ligand and the base and the strength of the base. The

techniques discussed in this chapter include urea

decomposition, vapor and aqueous gel diffusion, variation of

the solvent system and the base strength.


Urea Decomposition


Theory

Urea decomposes into two molecules of ammonia and one

carbon dioxide when it reacts with water. The relatively slow

27








28
reaction rate is increased by heat or a large concentration of

acid or base. Since urea is very water soluble, it is easily

dissolved in a dilute aqueous solution of an aluminum salt and

the ligand.

Experimental

Solutions with a three-to-one molar ratio of ligand to

aluminum ion were prepared by dissolving the 1.0 and 0.3

mmoles of the ligand and Al(NO3) 3.9H20, respectively, in 30 mL

of water. The ligands tested were pic, mpic, dipic, pza and

hyp. Upon gentle heating, 43 to 450C, ammonia, as well as

carbon dioxide bubbles, was gradually produced throughout the

solution and the compound was formed.

Results

For each ligand, the crystals that formed were neither

large nor of high quality. There was a very large incidence

of twinned crystals and inseparable clusters of crystalline

product, possibly as a result of the higher temperature.


Vapor Diffusion


Theory

One common technique to control the availability of the

reactants is through diffusion.61'62 By allowing the reactants

to only slowly combine, the reaction proceeds at a slower rate

than the formal concentrations would normally predict. As a

result larger crystals are generally produced. For vapor

phase diffusion, a gaseous reactant is slowly incorporated








29
into the other reactants, usually confined to an aqueous

phase.

Experimental

Ammonia is a fairly volatile gas as well as a moderate

base. Because of its volatility, it can slowly be absorbed

into a solution of the aluminum ion and the ligand. An

ammonia chamber was created by sealing a large beaker

containing two small beakers or vials. One of the beakers

contains an aqueous ammonia solution and the other contains

the rest of the reactants. After sealing, the chamber becomes

saturated with ammonia vapor which diffuses into the acidic

aluminum ion and ligand solution. The solutions for the vapor

diffusion experiments were prepared by dissolving the ligand

and Al(N03)39H20O in water as depicted in Table 3-1.

Results

After several days, a crystalline product began to form

in each experiment indicated. However, either the crystals

were too small or in inseparable clusters. The ammonia

reacted immediately upon contact with the surface of the

solution. Instead of single large crystals growing, clusters

formed and clung to the surface. The only single crystals

discovered were on the bottom of the beaker. Apparently, as

these single crystals grew, they became too heavy to be

supported by the surface tension of the solution and sank to

the bottom of the beaker. The clusters which continued to

grow on the surface probably did not sink to the bottom of the










Table 3-1.
Results.


Vapor Diffusion Experimental


30

Conditions and


Ligand [ligand], M [Al3] M Result

pic 0.010 0.010 no solid
0.020 0.010 crystalline
0.030 0.010 crystalline
0.045 0.015 crystalline
mpic 0.010 0.010 no solid

0.020 0.010 no solid
0.030 0.010 crystalline
0.045 0.015 crystalline
dipic 0.016 0.008 crystalline
pza 0.010 0.033 crystalline


beaker because of the increased surface tension created by the

irregular surface. Once a single crystal sank to the bottom,

it did not grow any larger because the crystal growth only

occurred at the interface. Because of these limitations,

vapor diffusion is not an effective crystal growth technique

for the compounds under investigation.


Gel Diffusion

Theory

Vapor diffusion is limited because the reaction is

dependent upon the diffusion in only one direction. In

addition, the rates of diffusion through air and aqueous

solutions are fairly rapid. Diffusion of water soluble

compounds through an aqueous gel matrix is much slower.








31
Because diffusion is slower, a concentration gradient is

produced over the distance from the interface.62 Also, the

semisolid gel is strong enough to support the crystals once

they form and flexible enough to not restrict growth as the

crystals enlarge. Aqueous gel diffusion is particularly

suited for these syntheses because the reactants are water

soluble and the products are insoluble. In addition, the

technique is regarded as a good method for the production of

large single crystals.62

Experimental

The agar gel used in the experiments was prepared by

dissolving the prescribed percentage of agar by weight in

water and heating to 980C. The solution was allowed to boil

at this temperature for 5 minutes and then cooled. Reagents

added to the agar were first dissolved in the minimum amount

of water and then completely mixed into the agar solution

before it hardened. The agar was poured into a large vial

with a screw top to ensure minimal solvent loss. To provide

a consistent reaction interface, any air bubbles were removed

using a disposable pipette before the agar set. Experiments

performed and results obtained are summarized in Table 3-2.

Results

A crystalline product was produced in most of the

experiments. The exceptions were when a white band was

produced in every case using hyp and twice with mpic. The

white band indicates that either very fine crystals formed or










Table 3-2.
Results.


Gel Diffusion Experimental


Conditions and


Bottom layer Top layer JLigand Results

0.010 M A13+ 0.030 M solution pic twins
in 1% agar of the sodium mpic white band

salt of the dipic small crystals
ligand pza fine crystals

___hyp white band
0.010 M sodium Single mpic white band
salt of ligand Al(NO3)3.9H20 pza flower-like
in 0.5% agar crystal hyp white band
0.1 mM NaOH in Aqueous solution pic twinned
1% agar and a of 0.03 M Al3+ mpic small crystals
thin layer of and 0.10 M of dipic small crystals
pure agar on the ligand pza flower-like
top hyp white band
1.0 mM NaHCO3 Aqueous solution pic small crystals
in 0.5% agar of 0.006 M A13+ mpic small crystals

and 0.020 M of dipic good crystals*
the ligand pza flower-like
0.10 M pic and 0.10 M solution pic twinned and
0.03 M Al3 in sodium acetate double-twinned
1% agar crystals
0.10 M pic and 0.10 M solution pic twinned and
0.03 M Al3" in sodium acetate double-twinned
1% agar crystals

* See Chapter 8 for structure








33
only Al(OH)3 was produced. Although most of the products were

crystalline, only one experiment yielded single crystals of

the size and quality required for x-ray diffraction studies.

The structure for this compound is presented in Chapter 6.

All of the trials with picolinic acid gave similar

results. Large crystals were produced, however, all of these

were either twinned or double-twinned. Twinned crystals are

formed when two crystals grow together along a common face,

frequently producing a mirrored effect. Because the lattice

pattern in a twin may not be constant throughout the sample,

the x-rays would probably be diffracted differently than they

would in a single crystal of the same compound. As a result,

twinned crystals are not usually suitable for x-ray

diffraction studies.61 Pyrazinoic acid consistently produced

fairly large crystalline structures that were flower-like in

appearance. Examination with a microscope revealed that each

had the four striated branches arranged in a tetrahedral

orientation around a central point. Although they were large

enough, the crystalline products were not single crystals.

The other crystals formed in the experiments were too small to

be useful for x-ray crystallography.


Base Strength


Theory

The syntheses discussed utilized moderately strong bases

that are stronger than needed to deprotonate the ligands. In








34
the presence of either a weak base or a low concentration of

a moderate base, the reaction should proceed slowly. In

addition, if the conjugate acid formed from the base is

volatile, the equilibrium will constantly shift towards the

products as the gaseous product evaporates. Furthermore,

because the chemical species present can alter crystal growth,

the production of twinned crystals and flower-like clusters

might not occur.

Experimental

Unless otherwise specified, the aluminum salt used was

Al(N03)3-9HO2. All reactions were performed in aqueous systems

and the ligand to aluminum ion ratio was three-to-one. The

specific quantities and compounds used in the reaction are

shown in Table 3-3.

Results

No suitable crystals were formed except for the

KAl(S04)2*12H20 reactant. However, the reactivity of the

ligands can be studied. The sulfate ion, with Kb of 8.3x10-13,

is too weakly basic to react to produce an aluminum compound.

The acetate ion, with a Kb of 5.6x10-10, was basic enough to

produce a crystalline product except for hypoxanthine, which

is a very weak acid. Although the reactions did proceed

slower than with the concentrated bicarbonate ion as the base,

single large crystals were not produced. The brown solution

produced in the reaction with hypoxanthine was probably due to

the ligand decomposing into a mixture of smaller amines.










Table 3-3. Base Variation Experimental Conditions and Results.

Ligand Base Time Results

0.40 M pic 0.27 M S042 from overnight KAl (SO04) 2- 12H20
KAl (SO4)2 crystals formed
0.10 M pic 0.10 M NaC2H302 10 min fine crystals
0.10 M pic 0.077 M NaC2H302 20 min fine crystals
0.10 M pic 0.070 M NaC2H302 30 min small crystals
7.5 mM pic 7.5 mM NaC2H3O2 1 week no solid product
50 mM pic 2 M NaC2H302 and no solid product
9 M HC2H302
14 mM pic 14 mM NH4C2H302 overnight twinned crystals
11 mM pic 0.44 M NH4C2H302 no solid product
and .07 M HC2H302
in 50 % acetone
20 mM pic 20 mM NaHCO3 30 min twinned crystals
14 mM pic 14 mM NaHCO3 2 hours twinned crystals
7.5 mM pic 7.5 mM NaHCO3 overnight powdery solid
0.30 M pic 0.30 M pyridine 2 min powdery solid
0.15 M pic 0.018 M pyridine overnight crystalline
15 mM dipic 7.5 mM SO42- from no solid product
Al2 (SO4)3" 18H20 pH rose from 1.5
to 4.5 overnight
8.3 mM 8.3 mM NaC2H302 3 days small crystals
dipic
15 mM pza 7.5 mM S042- from no solid product
Al2 (SO4) 2- 18H20
6.4 mM pza 7.7 mM NaC2H302 overnight flower-like
clusters
11 mM hyp 0.44 M NH4C2H302 2 weeks brown solution,
and .07 M HC2H302 no solid product
in 50 % acetone










Solvent System


Theory

When a crystal forms, occasionally solvent molecules are

incorporated to fill a space produced by the packing

arrangement. When a different solvent is used, the size and

shape of the new solvent may cause the molecules to pack in a

different manner. A possible result would be for the crystals

to grow differently. Crystallization in a series of solvents

is a common technique for the production of diffraction

quality crystals."61

Experimental

All syntheses were performed with a three-to-one ligand

to aluminum ion ratio. Unless otherwise noted, the

concentration of the ligand is equivalent to the concentration

of the base. The source of the aluminum ion was Al(N03)3-9H20.

The experimental conditions and results are presented in Table

3-4.

Results

Experiments performed in methyl or ethyl alcohol did not

produce a compound other than the sodium salt of the ligand

unless a substantial amount of water was present. However, in

the presence of water, pic and pza produce characteristic

unsuitable crystal forms. In DMSO, pic and pza both produced

a white solid that when heated to 1000C to remove water, a

clear but brightly colored solution was formed. It is

possible that the solution's color was due to a decomposition










Table 3-4. Experimental Conditions
Various Solvents and Results.


for Crystal Growth in


Solvent Base Ligand Notes
CH30H 0.10 M NaOH pic 65C, no solid product
CH30H 0.10 M NaHCO3 pic 500C, no solid product
C2H5OH 0.15 M NaOH pic 60C, no solid product
C2HgOH 0.030 M NaHCO3 pic 40C, no solid product
C2H5OH 0.033 M NaHCO3 pic 500C, sodium picolinate
precipitated
75% C2H5OH 0.15 M NaHCO3 pic overnight, twinned
crystals at room temp
50% C2H50H 0.15 M NaHCO3 pic opaque solution within
30 minutes at room temp
25% C2H5OH 0.15 M NaHCO3 pic opaque solution within
5 minutes at room temp
C2HsOH 7 mM NH4C2H302 pic room temp, no solid
HOCH2CH20H 0.15 M NaHCO3 pic 45C, no solid product
DMSO 0.53 M NaHCO3 pic white solid formed;
when heated to 1000C,
formed a clear peach
solution, no solid ppt
C2H5OH 0.045 M NaOH pza 600C, no solid product
C2HsOH 0.034 M NaOH pza 40C, no solid product
C2HsOH 5 mM NaHCO3 pza overnight at 500C,
flower-like clusters
DMSO 0.53 M NaHC03 pza white solid formed;
when heated to 1000C,
formed a clear bright
yellow solution, no
solid remained
C2HsOH 0.093 M NaOH 4.7 mM 450C, sodium salt of
_______dipic dipicolinic acid formed








38

product because the sodium salts of pic and pza produced the

same results when heated to 100C in DMSO. In addition, no

solid remained after the evaporation of the heated DMSO

reaction mixture.


Aluminum Isopropoxide


Theory

Used in the Meerwein-Ponndorf-Verley reduction, aluminum

isopropoxide, Al (OC3H,) 3, could provide an alternative aluminum

reagent for a synthesis in a non-aqueous environment.63 In

theory, in the presence of a ligand with a hydroxyl group, one

of the isopropoxide groups could exchange with the ligand to

form free isopropyl alcohol. Removal of the isopropanol by

evaporation or distillation should drive the reaction towards

completion. This would produce a coordination compound

synthesized in the absence of water.

Experimental

In a glove bag flushed with nitrogen gas, aluminum

isopropoxide (0.80 g, 3.9 mmole) was transferred to a dried

weighing bottle. Pyrazinoic acid (0.52 g, 4.2 mmole) was

added as a solid. Isopropyl alcohol was dried over anhydrous

CaS04 and 20 mL was added to the solids. The bottle was

capped and transferred to a desiccator. After five days, a

white solid, which had formed on the bottom of the bottle, was

collected by filtration. Comparable experiments were









39
performed for pic and mpic, however, no solid was produced in

either experiment.

With no effort to exclude atmospheric water, preweighed

aluminum isopropoxide (2.6 g, 12 mmole) was stirred in 30 mL

of isopropyl alcohol. Approximately 25 mL of a viscous

solution was collected after the mixture was centrifuged to

remove any solid. Picolinic acid (1.3 g, 11 mmole) was

dissolved in 20 mL of isopropyl alcohol. The solutions were

combined and within 30 minutes, the mixture began to cloud.

After 24 hours, the solution was filtered, the solid washed

with isopropanol and tested for solubility. A similar

experiment was performed for pza with solid formation being

instantaneous.

Results

The solids formed using aluminum isopropoxide were non-

crystalline. Furthermore, the products were not soluble in

any solvent and therefore could not be recrystallized.


Summary of Results


Although crystalline solids of the various complexes can

be readily formed using a variety of techniques, good single

crystals are very difficult to produce. Since the compounds

with pic and pza formed the same crystal forms under a variety

of conditions, it seems that packing of the molecules within

the crystal could be the cause. A probable conclusion would









40

be that x-ray quality crystals may never be grown for these

compounds.













CHAPTER 4
SYNTHESIS, STRUCTURE AND AL-27 NMR STUDIES OF COMPLEXES
WITH OXINE AND 2-METHYLOXINE


Introduction

Oxine(ox) and 2-methyloxine(meox), shown in Figure 4-1,

contain the same N,O donor group. Oxine has been extensively


HO HO

N N CH3





Figure 4-1. Oxine, left; 2-Methyloxine, right.


studied for uses as a completing agent for the quantitative

analysis of metal ions."4 The crystal structure of the

tris(oxinato)aluminum(III) with an occluded acetonylacetone

molecule was reported in a 1980 abstract as a distorted

octahedron with a meridional conformation.30 Two more recent

investigations confirm the structure of a tris complex between

the Al(III) ion and oxine.25'31 A drawing of the complex is

given in Figure 4-2.31 2-Methyloxine differs from oxine by the

substitution of a methyl group for the hydrogen alpha to the

nitrogen atom. The location of the methyl group could produce

















H25


Figure 4-2. ORTEP Drawing of the Tris(oxinato)aluminum(III)
without the Occluded Acetonylacetone. Ul-Haque, Horne, and
Lyle, J. Cryst. Spec. Res., 1991, 21, 411-417.








43
steric strain and interfere with the nitrogen coordination to

a metal ion. The only complex involving aluminum(III) and 2-

methyloxine that has been characterized by x-ray

crystallography seems to reinforce the steric argument. As








C38
C4 C46 C37, )"C39









C44 0 O C42






03






C29





Figure 4-3. PLUTO Line Drawing of the A-Oxo-di(bis(2-
methyloxinato)aluminum(III) Complex. Kushi and Fernando,
Journal of the American Chemical Society, 1970, 92, 91-95.








44

shown in Figure 4-3, the aluminum ion in u-oxo-di(bis(2-

methyloxinato) -aluminum(III)) is five coordinate with only two

2-methyloxine ligands each.3

The synthesis and characterization using x-ray

diffraction techniques of the tris complex Al(meox)3, as well

as Al(ox)3, are presented in this chapter. An ORTEP drawing

of each is included to display the distorted octahedral

environment around each aluminum ion. In addition, the

results of the Al-27 NMR analysis, including spectra, are

discussed for each complex.


Experimental


Synthesis

Materials. All materials and solvents were reagent grade

and used as supplied from manufacturer.

Preparation of Al(meox)3, CH3OH-H20 (I). DMSO (39 mL) was

placed in a 200 mL round bottom flask which was set in a 900C

oil bath to warm. A12(SO4)3 18 H20 (3.31 g, 10 mmole Al(H20)63)

was added and dissolved by stirring. 2-Methyloxine (5.02 g,

32 mmole) was subsequently added to yield a dark amber

solution. The solution was neutralized slowly by the addition

of 0.5 mL portions of diethylamine (7.5 mL, 72 mmol). The

resulting opaque mixture was stirred and heated for an

additional 10 minutes and then cooled to room temperature. A

dark amber solution (30 mL) was obtained by filtration through

a fine glass frit. After two months, large brown crystalline








45
clumps formed which were then redissolved in 15 mL methanol

and covered to slowly recrystallize. In two months, small

brown needles of diffraction quality were separated from the

solution.

Preparation of Al(ox)3-CH30H (II). To avoid the lengthy

recrystallization required with I, the synthetic scheme was

modified to exclude DMSO. Al(N03)3-9H20 (0.181 g, 0.5 mmole)

was dissolved in 150 mL of H20. Oxine (0.220 g, 1.5 mmole)

was added as a solid and slowly dissolved in the acidic

aqueous solution to yield a pale yellow solution. The pH of

the mixture was slowly raised by dropwise additions of NaOH

until a very, thick yellow precipitate formed at pH = 5.2.

The solid was collected by filtration and recrystallized from

95% ethanol. Diffraction quality crystals were obtained by

recrystallization of the solid from the solution.

Aluminum-27 NMR Spectroscopy

Preparation of Al(meox)3 (Ia). 2-Methyloxine (4.81 g,

30.2 mmole) was added to 200 mL H20. NaOH (1.21 g, 30.2

mmole) was added to dissolve the ligand. Al(N03)3-9H20 (3.79

g, 10.1 mmole) was dissolved in 50 mL H20 and added dropwise

to the clear brown solution to form a thick yellow

precipitate. After complete addition, the mixture was stirred

for 10 minutes. The solid was collected by filtration through

a glass frit, washed thoroughly with H20 and absolute C2HSOH

and dried. Elemental analysis: 69.79 % C, 4.70 % H, 8.12 % N








46

for Ia. 69.36 % C, 5.04 % H, 8.09 % N for Al(meox)3-H20.

Submitted for Al-27 NMR analysis.

Preparation of Al(ox)3 (IIa). Oxine (4.51 g, 31.1 mmole)

dissolved in 50 mL 100% C2HsOH to give dark amber solution.

Al(N03)3-9H20 (3.81 g, 10.2 mmole) was added to mixture with

stirring and a thick yellow precipitate formed. NaOH solution

was added until reaction cleared and then reformed a

precipitate. The bright yellow solid was collected by

filtration, washed thoroughly with H20 and C2HsOH, and dried.

Elemental analysis: 68.02 % C, 4.62 % H, 8.06 % N for IIa.

68.91 % C, 4.79 % H, 8.31 % N for Al(ox)3HC2HsOH. Submitted

for Al-27 NMR analysis.

Preparation of saturated Al (ox) 3-CHOH solution (IIb).

IIa (0.5 g, 1 mmole) was added to 350 mL 100% C2HsOH and

stirred at room temperature for 1 hour. A bright yellow

solution was collected by filtration through a glass frit and

evaporated slowly to yield 50 mL of a dark orange solution.

Recrystallization of a small fraction yielded exclusively one

crystal form of fluorescent yellow crystals, confirmed by X-

ray crystallography to be Al(ox)3"C2Hs5H. The solution was

submitted for Al-27 NMR analysis.

Al-27 NMR spectral analysis. Al-27 NMR spectra were

collected on a NT-300 NMR spectrometer with spectrometer

frequency 78.176839 MHz. The samples were spun at the magic

angle at rates of 1.4 and 2.05 kHz for Ia and IIa,

respectively.










X-ray Crystallocrraphic Analysis

X-ray diffraction study of I. A needle shaped crystal

having the dimensions 0.22 x 0.16 x 0.14 mm was mounted on a

glass fiber for diffraction studies. All subsequent data were

collected on a Nicolet P3 Diffractometer, using filter-

monochromated Cu Ka radiation for I. The unit cell dimensions

were determined for 25 automatically centered reflections;

space group tetragonal P4/n by intensity statistics and

satisfactory structure solution and refinement; 2020 unique

reflections, 1945 with I>3a(I); 0shs10, 0sksl0, Oslsl0. Two

intensity standards, which were measured every 98 reflections,

showed no change during data collection. The program used for

Foba refinement was SHELXTL Revision 5.1 (Sheldrick, 1985) All

non-hydrogen atoms were located from an E-map. Twenty of the

thirty hydrogen atoms were located using a difference Fourier

map. Final refinement values for 361 parameters were R =

8.67, wR = 10.67 and w = 9.07. Calculations and figures were

performed on an Eclipse Model 30 desktop computer. Atomic

scattering factors used in the SHELXTL program are the

analytical form given in International Tables for X-ray

Crystallography (1974).

X-ray diffraction study of II. Method and

instrumentation used to solve the X-ray structure of II were

the same as above with the following exceptions. A tabular

crystal having the dimensions 0.32 x 0.32 x 0.10 mm was

mounted. The data were collected using graphite-monochromated








48
Mo Ka radiation. The unit cell dimensions were determined for

17 automatically center reflections, 1.00s28e30.0; space

group monoclinic P21/n; 1421 unique reflections, 1062 with

I>3a(I), 0shs8, OskslO, -13sls13. Eighteen of the twenty-two

hydrogen atoms were located using a difference Fourier map.

Final refinement values for 325 parameters were R = 9.18, wR

= 7.15 and w = 7.13.


Discussion

X-ray diffraction analysis

Crystallographic data for each complex is summarized in

Table 4-1.

Al(meox)3 COH_ HO (I). An ORTEP drawing of the

Al(meox)3 molecule is given in Figure 4-4. Final atomic

coordinates for all non-hydrogen atoms and all hydrogen atoms

found, bond lengths and bond angles appear in Tables 4-2

through 4-5, respectively. The anisotropic thermal parameters

are listed in Table 4-6.

Despite the presence of the sterically hindering methyl

group adjacent to the nitrogen atom, the aluminum ion is

definitely coordinated to the nitrogen and oxygen atoms of

three 2-methyloxine ligands. The Al-N bond distances in I,

ranging from 2.122 to 2.179 A, correspond well with the

relatively long Al-N bond distance of 2.18 A reported for

H3A12N(CH3)3.65 However, the Al-N bonds in I are significantly

longer than the Al-N bonds in /-oxo-di(bis(2-methyloxinato)











Table 4-1. Crystallographic Data for I and II.


Complex

Formula

MW

Crystal system

Space Group

a, A

b, A

c, A

3, o

Vc, A3

z

Dcaic, g/cm3

Radiation

X, A

A cm-1

F(000)

Crystal
dimensions
28

Observed
reflections
Collected
reflections
Number of
parameters
Final R


Al (meox) 3- CH3OH- H20

AlC31H3oN30s

551.55

Tetragonal

P4/n

22.1970

22.1970

11.1804

90.000

5508.6

8

1.33

Cu Kae

1.54178

8.95

2095.61

0.22 x 0.16 x 0.14

0.0, 100.0

2020

1945

361

0.0867

0.1067


II

Al (ox) 3" CH3OH

AlC2,H22N304

491.48

Monoclinic

P21/n

10.8620

13.2381

16.8528

97.511

2402.5

4

1.36

Mo Ka

0.71069

4.49

951.81

0.32 x 0.32 x 0.10

1.0, 30.0

1421

1062

325

0.0918

0.0715













C(25)


C(35)


C(37)


Figure 4-4. ORTEP Drawing of the Al(meox)3
the Atomic Numbering Scheme and the Thermal


Molecule Showing
Ellipsoids.









Table 4-2. Final Atomic Coordinates (xl04) and Isotopic
Thermal Parameters (A2X103) for I. Estimated Standard
Deviations are given in Parentheses.


x y z U
Al 0.8192 (1) 0.4832 (1) 0.1185 (2) 46 (1)
0(1) 0.8291 (2) 0.5569 (2) 0.0533 (5) 57 (2)
N(1) 0.7596 (3) 0.4725 (3) -0.0348 (5) 48 (2)
C(11) 0.7611 (4) 0.5262 (4) -0.0956 (7) 50 (3)
C(12) 0.7996 (3) 0.5700 (4) -0.0488 (8) 52 (3)
C(13) 0.8048 (4) 0.6254 (4) -0.1064 (8) 60 (4)
C(14) 0.7716 (4) 0.6351 (5) -0.2123 (8) 75 (4)
C(15) 0.7360 (4) 0.5926 (4) -0.2612 (8) 72 (4)
C(16) 0.7295 (4) 0.5362 (4) -0.2054 (7) 56 (3)
C(17) 0.6956 (4) 0.4883 (5) -0.2484 (8) 68 (4)
C(18) 0.6939 (4) 0.4347 (4) -0.1891 (8) 58 (3)
C(19) 0.7251 (3) 0.4276 (4) -0.0781 (7) 50 (3)
C(10) 0.7220 (4) 0.3667 (4) -0.0192 (8) 78 (4)
0(2) 0.8687 (2) 0.5023 (2) 0.2471 (4) 51 (2)
N(2) 0.9011 (3) 0.4510 (3) 0.0434 (5) 44 (2)
C(21) 0.9443 (3) 0.4564 (3) 0.1302 (6) 44 (3)
C(22) 0.9263 (4) 0.4830 (4) 0.2399 (7) 54 (3)
C(23) 0.9659 (3) 0.4875 (4) 0.3339 (7) 55 (3)
C(24) 1.0262 (4) 0.4667 (4) 0.3176 (7) 63 (4)
C(25) 1.0447 (4) 0.4420 (4) 0.2131 (8) 60 (3)
C(26) 1.0040 (4) 0.4367 (4) 0.1162 (7) 50 (3)
C(27) 1.0201 (4) 0.4124 (4) 0.0016 (7) 53 (3)
C(28) 0.9774 (3) 0.4079 (3) -0.0848 (7) 50 (3)
C(29) 0.9172 (4) 0.4273 (3) -0.1629 (7) 57 (3)
C(20) 0.8725 (4) 0.4221 (4) -0.1629 (7) 57 (3)
0(3) 0.8059 (2) 0.4060 (2) 0.1692 (4) 51 (3)
N(3) 0.7455 (3) 0.5022 (3) 0.2332 (5) 49 (2)
C(31) 0.7314 (3) 0.4496 (4) 0.2893 (7) 51 (3)
C(32) 0.7656 (4) 0.3987 (4) 0.2537 (7) 53 (3)
C(33) 0.7542 (4) 0.3423 (4) 0.3063 (8) 71 (4)
C(34) 0.7092 (5) 0.3378 (5) 0.3980 (9) 83 (4)
C(35) 0.6764 (4) 0.3870 (6) 0.4337 (8) 85 (5)
C(36) 0.6866 (4) 0.4447 (5) 0.3822 (7) 64 (4)
C(37) 0.6561 (4) 0.5004 (5) 0.4062 (7) 73 (4)
C(38) 0.6687 (4) 0.5510 (5) 0.3514 (9) 71 (4)
C(39) 0.7148 (4) 0.5521 (4) 0.2593 (7) 66 (3)
C(30) 0.7277 (4) 0.6110 (4) 0.1977 (10) 90 (4)
0(4) 0.8433 (3) 0.5559 (3) 0.4583 (6) 94 (3)
C(4) 0.8249 (5) 0.5063 (6) 0.5319 (10) 112 (6)
0(5) 0.6755 (3) 0.7031 (3) 0.4787 (7) 117 (4)

Equivalent isotropic U defined as one third of the trace of
the orthogonalized Uj tensor










Table 4-3. Hydrogen Atom Coordinates (x104) for I.


H(13)
H(14)
H(15)
H(17)
H(18)
H(101)
H(24)
H(25)
H(27)
H(28)
H(201)
H(202)
H(33)
H(34)
H(35)
H(37)
H(38)
H(301)
H(302)
H(5)


x

0.8434
0.7812
0.7028
0.6493
0.6544
0.7131
1.0569
1.0875
1.0614
0.9869
0.8500
0.8388
0.7949
0.7034
0.6609
0.6266
0.6482
0.7000
0.7772
0.6325


y

0.6558
0.6715
0.6083
0.4771
0.4089
0.3604
0.4653
0.4191
0.3915
0.3763
0.4616
0.3809
0.3076
0.2863
0.3839
0.4813
0.6029
0.6511
0.6173
0.7075


x

-0.0747
-0.2853
-0.3354
-0.3092
-0.2414
0.0660
0.4023
0.1925
-0.0093
-0.1527
-0.1594
-0.1610
0.3074
0.4238
0.5353
0.4740
0.3477
0.2198
0.2270
0.4869


aluminum(III)) which range from 2.054 to 2.110 A.32 In

addition, they are even longer when compared to the Al-N bond

lengths of 2.028 to 2.073 A in tris(oxinato)aluminum(III).31

The steric interaction of the methyl groups with the aromatic

rings is probably responsible for the lengthening of the Al-N

bonds in the tris(2-methyloxinato)aluminum(III) complex. The

longest Al-N bond length and shortest Al-0 bond length are to

ring 1. A potential cause may be that the molecule is

twisting outward to allow more space between the methyl group

on ring 2 and ring 1.










Table 4-4. Bond Lengths (A) for I.
Deviations are given in Parentheses.


Estimated Standard


Al-O(1)
Al-0(2)
Al-O(3)
0(1) -C(12)
N(1) -C(19)
C(11)-C(16)
C(13) -C(14)
C(14)-C(15)
C(15)-C(16)
C(16)-C(17)
C(17)-H(17)
C(18)-H(18)
C(10)-H(11)
N(2) -C(21)
C(21) -C(22)
C(22) -C(23)
C(24) -C(25)
C(25) -C(26)
C(26) -C(27)
C(27) -H(27)
C(28) -H(28)
C(20) -H(21)
0(3) -C(32)
N(3) -C(39)
C(31) -C(36)
C(33) -C(34)
C(34) -C(35)
C(35)-C(36)
C(36) -C(37)
C(37) -H(37)
C(38) -H(38)
C(30) -H(31)
0(4) -C(4)


1.805(6)
1.858(5)
1.829(5)
1.347(10)
1.347(10)
1.430(11)
1.412(13)
1.347(14)
1.407(13)
1.389(13)
1.257(9)
1.200(8)
0.983 (9)
1.369(9)
1.418(11)
1.374(11)
1.354(12)
1.415(12)
1.435(11)
1.035(8)
1.055(7)
1.010(8)
1.311(9)
1.332(11)
1.441(11)
1.435(14)
1.371(16)
1.423 (16)
1.436(15)
1.087(9)
1.239(10)
1.111(10)
1.432(15)


Al-N(1)
Al-N(2)
Al -N(3)
N(1) -C(11)
C(11)-C(12)
C(12)-C(13)
C(13)-H(13)
C(14)-H(14)
C(15)-H(15)
C(17)-C(18)
C(18)-C(19)
C(19) -C(10)
0(2) -C(22)
N(2) -C(29)
C(21) -C(26)
C(23) -C(24)
C(24) -H(24)
C(25) -H(25)
C(27) -C(28)
C(28) -C(29)
C(29) -C(20)
C(20) -H(22)
N(3) -C(31)
C(31) -C(32)
C(32)-C(33)
C(33)-H(33)
C(34) -H(34)
C(35)-H(35)
C(37) -C(38)
C(38) -C(39)
C(39) -C(30)
C(30) -H(32)
0(5) -H(5)


2.179(6)
2.127(6)
2.122(6)
1.372(10)
1.398(12)
1.393 (12)
1.146(8)
1.168(10)
1.163(9)
1.361(14)
1.431(11)
1.504(12)
1.351(10)
1.362(9)
1.406(11)
1.429(12)
1.167(8)
1.102(8)
1.356(11)
1.422(11)
1.488(11)
1.181(8)
1.361(11)
1.419(12)
1.407(13)
1.186(9)
1.186(11)
1.190 ((9)
1.310(15)
1.452 (13)
1.505(13)
1.154(10)
0.964(7)


Table 4-5. Bond Angles (0) for I.
Deviations are given in Parentheses.


0(1) -Al-N(1)
0(1) -Al-0(2)
N(1) -Al-0(2)
0(1) -Al-N(2)
N(1) -Al-N(2)
0(2) -Al-N(2)
0(1) -Al-0(3)
N(1) -A-O0(3)


81.7(3)
92.0(3)
173.1(3)
92.4(2)
99.9(2)
83.0(2)
173.9(3)
92.5(2)


Estimated Standard


C(22) -C(23) -C(24)
C(23) -C(24) -C(25)
C(23) -C(24) -H(24)
C(25)-C(24) -H(24)
C(24) -C(25) -C(26)
C(24) -C(25) -H(25)
C(26) -C(25) -H(25)
C(21) -C(26) -C(25)


118.6(7)
121.7(8)
116.9(7)
120.9(8)
120.1(8)
128.9(8)
110.6(7)
119.4(7)










Table 4-5 -- Continued.


0(2) -Al-O0(3)
N(2) -Al-0(3)
0(1) -Al-N(3)
N(1) -Al-N(3)
0(2) -Al-N(3)
N(2) -Al-N(3)
0(3) -Al-N(3)
Al-O(1) -C(12)
Al-N(l)-C(11)
Al-N(1) -C(19)
C(11) -N(1) -C(19)
N(1) -C(11) -C(12)
N(1)-C(11)-C(16)
C(12)-C(11)-C(16)
0(1) -C(12) -C(11)
0(1) -C(12) -C(13)
C(11) -C(12) -C(13)
C(12)-C(13)-C(14)
C(12)-C(13)-H(13)
C(14) -C(13) -H (13)
C(13) -C(14) -C(15)
C(13) -C(14) -H(14)
C(15) -C(14) -H (14)
C(14)-C(15)-C(16)
C(14) -C(15) -H (15)
C(16)-C(15)-H(15)
C(11) -C(16) -C(15)
C(11)-C(16)-C(17)
C(15)-C(16)-C(17)
C(16) -C(17) -C(18)
C(16)-C(17)-H(17)
C(18)-C(17)-H(17)
C(17) -C(18) -C(19)
C(17)-C(18) -H(18)
C(19) -C(18) -H(18)
N(1)-C(19)-C(18)
N(1)-C(19) -C(10)
C(18)-C(19) -C(10)
C(19)-C(10)-H(101)
Al-0(2) -C(22)
Al-N(2) -C(21)
Al-N(2) -C(29)
C(21) -N(2) -C(29)
N(2) -C(21) -C(22)
N(2) -C(21) -C(26)
C(22) -C(21) -C(26)
0(2) -C(22) -C(21)
0(2) -C(22) -C(23)
C(21) -C(22) -C(23)


94.0(2)
86.8(2)
99.1(3)
91.6(2)
86.7(2)
164.8(3)
82.8(2)
118.6(5)
106.3(5)
135.1(5)
118.5(6)
115.7(7)
123.3(7)
120.9(8)
117.7(7)
122.8(7)
119.5(8)
118.6(8)
116.0(8)
124.1(8)
122.7(9)
126.6(9)
107.9(8)
120.2 (9)
116.8(9)
121.3 (8)
118.0(8)
116.3(8)
125.7(8)
121.0(8)
141.4(9)
93.9(7)
120.4(8)
101.5(7)
136.4 (8)
120.3 (7)
122.3(7)
117.2(7)
124.2(8)
116.1(5)
106.8(4)
134.7(5)
118.5(6)
116.9(7)
123.6(7)
119.5(7)
116.8(7)
122.4(7)
120.8(8)


C(21) -C(26) -C(27)
C(25) -C(26) -C(27)
C(26) -C(27) -C(28)
C(26) -C(27) -H(27)
C(28) -C(27) -H(27)
C(27) -C(28) -C(29)
C(27) -C(28) -H (28)
C(29) -C(28) -H(28)
N(2) -C(29) -C(28)
N(2) -C(29) -C(20)
C(28) -C(29) -C(20)
C(29) -C(20) -H(201)
C(29) -C(20) -H(202)
H(201) -C(20) -H(202)
Al-0(3) -C(32)
A1-N(3) -C(31)
A1-N(3) -C(39)
C(31) -N(3) -C(39)
N(3) -C(31) -C(32)
N(3) -C(31) -C(36)
C(32) -C(31) -C(36)
0(3) -C(32) -C(31)
0(3) -C(32) -C(33)
C(31) -C(32) -C(33)
C(32) -C(33) -C(34)
C(32) -C(33) -H(33)
C(34) -C(33) -H (33)
C(33) -C(34) -C(35)
C(33) -C(34) -H(34)
C(35) -C(34) -H (34)
C(34) -C(35) -C(36)
C(34) -C(35) -H(35)
C(36) -C(35) -H(35)
C(31) -C(36) -C(35)
C(31)-C(36)-C(37)
C(35) -C(36) -C(37)
C(36) -C(37) -C(38)
C(36) -C(37) -H(37)
C(38) -C(37) -H (37)
C(37) -C(38) -C(39)
C(37) -C(38) -H(38)
C(39) -C(38) -H(38)
N(3) -C(39) -C(38)
N(3) -C(39) -C(30)
C(38) -C(39) -C(30)
C(39) -C(30) -H(301)
C (39) -C(30) -H (302)
H(301) -C(30) -H(302)


116.8(7)
123.8(7)
119.4(7)
119.6(7)
120.1(7)
121.3(7)
114.9(7)
120.3(7)
120.4(7)
120.7(7)
118.9(7)
103.5(7)
118.0(6)
111.0(7)
116.6(5)
106.6(5)
133.8(6)
119.6(7)
115.5(7)
123.8(8)
120.7(8)
118.0(7)
122.2(8)
119.7(7)
119.0(9)
116.5(7)
118.5(8)
121.4(10)
108.5(9)
129.7(9)
121.0(9)
112.7(10)
119.0(10)
118.0(9)
113.3 (8)
128.7(8)
123.4(8)
94.5(9)
142.1(11)
119.8(9)
137.2(9)
102.7(8)
120.1 (8)
121.6(8)
118.2(8)
119.3(9)
99.0(8)
111.5(8)











Table 4-6. Anisotropic Temperature Parameters (A2 x 10') for
Non-Hydrogen Atoms for I. Estimated Standard Deviations are
given in Parentheses.


Atom

Al
0(1)
N(1)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(10)
0(2)
N(2)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(20)
0(3)
N(3)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(30)
0(4)
C(4)
0(5)


U11

41(1)
49(4)
39(4)
45(5)
35(5)
50(6)
80(8)
77(7)
45(5)
61(7)
45(6)
34(5)
107(8)
41(3)
47(4)
42(5)
57(6)
39(5)
56(6)
47(5)
41(5)
45(5)
54(5)
58(6)
61(6)
49(3)
42(4)
34(5)
44(5)
53(6)
79(8)
65(7)
39(5)
41(6)
71(7)
48(5)
80(7)
113(6)
94(9)
84(5)


U22

52(2)
61(4)
56(4)
51(5)
57(6)
51(6)
91(8)
74(7)
73(6)
86(8)
75(7)
64(6)
59(6)
72(4)
41(4)
48(5)
55(6)
78(6)
84(7)
72(6)
49(5)
50(5)
42(5)
36(5)
58(6)
55(3)
55(5)
72(6)
69(7)
86(7)
100(9)
148(11)
118(9)
133(10)
82 (7)
92 (7)
63(7)
94(5)
163(12)
129(7)


U33

47(1)
61(3)
47(4)
55(5)
63(3)
80(7)
54(6)
64(6)
51(5)
57(6)
54(5)
53(5)
70(6)
41(3)
44(4)
41(4)
51(5)
47(5)
49(5)
61(6)
61(5)
65(5)
55(5)
45(4)
51(5)
51(3)
51(4)
46(5)
47(5)
74(6)
71(7)
40(5)
37(5)
46(6)
61(6)
59(6)
126 (9)
75(4)
79(8)
136(7)


U23

-5(1)
-5(3)
-1(4)
-4(5)
-0(5)
2(5)
22(6)
15(6)
7(5)
-2(6)
-18(5)
-7(4)
10(5)
-15(3)
3(3)
4(4)
-5(5)
4(5)
-1(5)
-6(5)
4(5)
-1(5)
-15(4)
4(4)
-28(4)
-3(3)
-15(4)
-6(5)
9(5)
22 (6)
19(7)
6(6)
-20(6)
-18(6)
-17(6)
-21(5)
-28(7)
-30(4)
-5(8)
-8(5)


U13

-2(1)
-8(3)
7(3)
6(4)
9(5)
9(5)
8(6)
-17(6)
5(4)
-14(5)
-10(4)
7(4)
-9(6)
-6(3)
3(3)
4(4)
18(5)
-8(4)
-15(5)
-5(5)
7(5)
21(5)
-3(4)
6(4)
-4(5)
12(3)
-3(3)
-2(4)
-6(5)
6(5)
5(6)
-8(5)
-2(4)
13(5)
-12(6)
3 (4)
-0(7)
11(4)
19(7)
21(5)


The form of the thermal ellipsoid is exp[-27r2(h2a*2Un1
U22 + 12c*2 U33 + 2klb*c*U23 + 2hla*c*U,1 + 2hka*b*U12)]


U12

1(1)
-1(3)
2(3)
4(4)
1(4)
-5(4)
5(7)
14(6)
9(5)
-1(6)
-1(5)
-6(4)
-16(6)
4(3)
-8(3)
-8(4)
5(5)
-9(4)
-12(5)
7(5)
-2(4)
2(4)
6(4)
1(4)
9(5)
6(3)
5(3)
-6(4)
-2(5)
4(5)
-8(6)
-30(7)
-6(5)
-15(6)
12(6)
4(5)
27(6)
10(4)
-30(8)
6(5)

+ k2b*2








56

Al(ox) 3*CH30H (II). The ORTEP drawing of II is given in

Figure 4-5. Atomic coordinates for all non-hydrogen atoms and

hydrogen atoms found, bond lengths and bond angles are given

in Tables 4-7 through 4-10, respectively. The anisotropic

thermal parameters appear in Table 4-11.

As expected, the aluminum ion is in a distorted

octahedral environment created by three oxine ligands. The

three nitrogen and three oxygen atoms are arranged in the

meridional as opposed to the facial conformation. The complex

is isostructural with the Al(ox)3 molecule in a compound

previously reported.3

Although II is quite similar to I, there are notable

differences between the bond lengths and angles between the

aluminum, nitrogen and oxygen atoms for the two complexes. In

Al(meox)3, the Al-O bond lengths are 1.805, 1.829 and 1.858 A.

On the average, these are slightly shorter than the Al-O bond

distances in Al(ox)3 of 1.842, 1.845 and 1.884 A. In

addition, the Al-N bond lengths for Al-N bonds are longer for

Al(meox)3. The Al-N bond distances in I range from 2.122 to

2.179 A. In II, the Al-N bonds, which range from 2.026 to

2.077 A, are an average difference of 0.100 A shorter than for

the Al(meox)3 complex. As the bond to the oxygen gets

shorter, the ligand molecule pivots to also provide a longer

Al-N bond distance. As a result, the Al(meox)3 is distorted

farther from the ideal octahedron than Al(ox)3.




















0(3)


(17) C(16)


C(271


C(12) C(1


Figure 4-5. ORTEP of Al(ox)3 Molecule Showing the Atomic
Numbering Scheme and Thermal Ellipsoids.











Table 4-7. Final Atomic Coordinates (xl04) and Isotropic
Thermal Parameters (A2x10) for II. Estimated Standard
Deviations are given in Parentheses.


Atom

Al
0(1)
N(1)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
0(2)
N(2)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
0(3)
N(3)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
0(4)
C(4)


0.4265(3)
0.2599(5)
0.4464 (7)
0.5443(10)
0.5401(13)
0.4303 (16)
0.3236(12)
0.2008(12)
0.1072(11)
0.1220(9)
0.2367(8)
0.3355(8)
0.5956(5)
0.4551(6)
0.3771(9)
0.4186(11)
0.5385(12)
0.6254(9)
0.7559(11)
0.8301(10)
0.7783(9)
0.6537(8)
0.5780(7)
0.4114 (5)
0.3811(6)
0.3649(9)
0.3391(10)
0.3278(9)
0.3404(8)
0.3336(10)
0.3520(9)
0.3796(8)
0.3880(8)
0.3694(7)
0.9547(8)
0.9648(14)


0.0274(2)
0.0105(4)
0.0749(5)
0.1074(8)
0.1397(9)
0.1354(9)
0.1046(7)
0.0982(9)
0.0649(9)
0.0336(8)
0.0374(7)
0.0739(6)
0.0229(5)
-0.1228(5)
-0.1959(9)
-0.2922(9)
-0.3132(8)
-0.2414 (7)
-0.2558(7)
-0.1776(9)
-0.0833 (8)
-0.0632(7)
-0.1459(6)
0.1581(4)
-0.0107(5)
-0.0989(7)
-0.1056(9)
-0.0196(11)
0.0749(9)
0.1669(9)
0.2581(8)
0.2577(7)
0.1655(7)
0.0745(7)
0.0461(7)
0.1254 (13)


0.7389(2)
0.7561(3)
0.8542(4)
0.9009(7)
0.9793(8)
1.0089(7)
0.9626(6)
0.9863(7)
0.9317(9)
0.8527(6)
0.8287(6)
0.8841(5)
0.7371(3)
0.7720(4)
0.7901(5)
0.8134 (6)
0.8134(6)
0.7930(5)
0.7925(6)
0.7751(6)
0.7574(6)
0.7555(5)
0.7751(4)
0.7009(3)
0.6223(4)
0.5836(6)
0.5010(7)
0.4552(6)
0.4916(6)
0.4531(6)
0.4940(7)
0.5800(6)
0.6218(6)
0.5755(5)
0.3444(7)
0.3919(11)


* Equivalent isotropic U defined as one third of the trace of
the orthogonalized Upj tensor


38(1)*
42 (2)*
38(3)*
54 (5)*
66(6)*
77(6)*
51(5)*
76(5)*
71(6)*
50(4)*
39(4)*
40(4)*
33(2)*
30(3)*
43(4)*
55(5)*
57(5)*
37(4)*
52 (5)*
47(4)*
44(4) *
31(4) *
26(3)*
36(2)*
31(3)*
44 (4)*
59(5)*
56(5)*
44 (4)*
59(5)*
49(5)*
45(4)*
36(4)*
30(3)*
137 (5)*
178 (10)*










Table 4-8. Hydrogen Atom Coordinates (xl04) for II.


Atom

H(11)
H(12)
H(13)
H(15)
H(16)
H(17)
H(21)
H(22)
H(23)
H(25)
H(26)
H(27)
H(31)
H(32)
H(33)
H(35)
H(36)
H(37)


x

0.6093
0.6192
0.4324
0.2114
0.0293
0.0521
0.2834
0.3567
0.5486
0.7843
0.9172
0.8209
0.3750
0.3176
0.3096
0.3219
0.3406
0.3823


y

0.1143
0.1599
0.1558
0.1052
0.0557
0.0261
-0.1815
-0.3365
-0.3627
-0.3126
-0.1800
-0.0347
-0.1579
-0.1677
-0.0363
0.1658
0.3349
0.3264


z

0.8760
1.0192
1.0513
1.0335
0.9408
0.8154
0.7796
0.8245
0.8086
0.8011
0.7650
0.7443
0.6148
0.4742
0.4026
0.3898
0.4728
0.6163


The average intraligand O-Al-N bond angle for I is 82.50

which is slightly more acute than the average of 82.90 for II.

The interligand bond angles around aluminum range from 86.70

to 99.90 with an average of 92.80 for Al(meox)3. For Al(ox)3,

these bond angles, varying from 87.60 to 96.9, average to

92.50. The average of the bond angles for Al(ox)3 correspond

more closely to the 900 angles present in an ideal octahedron.

The comparison of the bond angles for the oxygen and

nitrogen atoms trans to each other corroborates that the

Al(ox)3 is closer to the ideal octahedral environment than

Al(meox)3. In I, the trans bond angles range from 164.80 to

173.90 for an average deviation 9.40 from an ideal 1800 angle.










Table 4-9. Bond Lengths (A) for II.
Deviations are given in Parentheses.


Estimated Standard


Al-O (1)
Al-0 (2)
Al-O(3)
N(1) -C(11)
C(11)-C(12)
C(12)-C(13)
C(13)-C(14)
C(14)-C(15)
C(15) -C(16)
C(16)-C(17)
C(17) -C(18)
C(18)-C(19)
N(2) -C(21)
C(21) -C(22)
C(22) -C(23)
C(23) -C(24)
C(24) -C(25)
C(25)-C(26)
C(26) -C(27)
C(27) -C(28)
C(28)-C(29)
N(3) -C(31)
N(3) -C(31)
C(31)-C(32)
C(32) -C(33)
C(33)-C(34)
C(34)-C(35)
C(35) -C(36)
C(36) -C(37)
C(37)-C(38)
C(38) -C(39)


1.884 (6)
1.842 (6)
1.845(6)
1.310(13)
1.395(18)
1.352(22)
1.372(19)
1.445(19)
1.353(17)
1.423(19)
1.360(14)
1.413 (12)
1.347(13)
1.393(16)
1.332(17)
1.413 (16)
1.431(16)
1.367(16)
1.387(15)
1.375(14)
1.434 (13)
1.339(12)
1.339(12)
1.385(15)
1.372(18)
1.392(19)
1.413(17)
1.357(16)
1.441(15)
1.406(14)
1.435(13)


Al -N(1)
Al -N (2)
Al -N (3)
0(1)-C(18)
N(1) -C(19)
C(11)-H(11)
C(12) -H(12)
C(13) -H(13)
C(14)-C(19)
C(15)-H(15)
C(16) -H(16)
C(17) -H(17)
0(2) -C(28)
N(2) -C(29)
C(21) -H(21)
C(22) -H(22)
C(23)-H(23)
C(24) -C(29)
C(25) -H(25)
C(26) -H(26)
C(27) -H(27)
0(3) -C(38)
N(3) -C(39)
C(31) -H(31)
C(32) -H(32)
C(33)-H(33)
C(34) -C(39)
C(35)-H(35)
C(36) -H(36)
C(37) -H(37)
0(4) -C(4)


2.026(8)
2.077(8)
2.026(7)
1.329(12)
1.365(12)
0.872(12)
1.054(13)
0.761(12)
1.407(14)
0.793(11)
0.888(12)
0.926(10)
1.320(11)
1.363(10)
1.028(10)
0.930(12)
0.670(10)
1.383(12)
0.818(10)
0.983 (10)
0.839(11)
1.328(11)
1.372(11)
0.940(10)
0.953(12)
0.910(11)
1.409(12)
1.059(10)
1.080(11)
1.094(10)
1.316(21)


Table 4-10. Bond Angles (o) for II.
Deviations are given in Parentheses.


Estimated Standard


0(1) -Al-N(1)
0(1) -Al-0(2)
N(1) -Al-0(2)
0(1) -Al-N(2)
N(1) -Al-N(2)
0(2) -Al-N(2)


82.8(3)
168.3 (3)
92.5(3)
87.6(3)
92.7(3)
81.9(3)


C(21) -C(22) -H (22)
C(23) -C(22) -H(22)
C(22) -C(23) -C(24)
C(22) -C(23) -H (23)
C(24) -C(23) -H (23)
C(23) -C(24) -C(25)


114.7(11)
127.0(12)
122.9(10)
112.3(15)
120.2(15)
127.2 (9)










-- continued.


0(1) -Al-0(3)
N(1) -Al-0(3)
0(2) -Al-0(3)
N(2) -Al-0(3)
0(1) -Al-N(3)
N(1) -Al-N(3)
0(2) -Al-N(3)
N(2) -Al-N(3)
0(3) -Al-N(3)
Al-O(1) -C(18)
Al-N (1) -C (11)
Al-N(1) -C(19)
C(11) -N(1) -C(19)
N(1)-C(i1)-C(12)
N(1)-C(11)-H(11)
C(12)-C (11) -H (11)
C(11) -C(12) -C(13)
C(11) -C(12) -H(12)
C(13) -C(12) -H(12)
C(12) -C(13) -C(14)
C(12)-C(13) -H(13)
C(14) -C(13) -H (13)
C(13)-C(14)-C(15)
C(13) -C(14) -C(19)
C(15) -C(14) -C(19)
C(14) -C(15) -C(16)
C(14) -C(15) -H(15)
C(16) -C(15) -H(15)
C(15)-C(16) -C(17)
C(15)-C(16)-H(16)
C(17) -C(16) -H (16)
C(16) -C(17)-C(18)
C(16) -C(17) -H (17)
C(18) -C(17) -H(17)
0(1)-C(18) -C(17)
0(1)-C(18)-C(19)
C(17)-C(18) -C(19)
N(1) -C(19) -C(14)
N(1) -C(19) -C(18)
C(14) -C(19) -C(18)
Al-0(2) -C(28)
A1-N(2) -C(21)
A1-N(2) -C(29)
C(21) -N(2) -C(29)
N(2) -C(21) -C(22)
N(2) -C(21) -H(21)
C(22) -C(21) -H(21)
C(21)-C(22) -C(23)


96.9(3)
92.0(3)
93.9(3)
173.9(3)
90.1(3)
171.5(3)
95.3(3)
91.8(3)
84.1(3)
114.3(5)
130.9(8)
111.2(5)
117.9(8)
123.0(11)
112.9(11)
123.6(11)
118.5(11)
123.9(13)
117.3 (12)
121.5(11)
114.4(17)
123.9(19)
127.0(11)
116.5(12)
116.5(9)
118.0(11)
104.6(12)
135.8(15)
124.4 (12)
125.2(16)
110.3 (12)
119.2(9)
118.9(11)
120.2(11)
123.8(8)
118.7(8)
117.5(9)
122.6(8)
113.0(8)
124.4(9)
118.1(6)
132.2(6)
109.7(5)
118.2(7)
122.1(9)
117.9(10)
119.6(10)
118.2(11)


C(23) -C(24) -C(29)
C(25) -C(24) -C(29)
C(24) -C(25) -C(26)
C(24) -C(25) -H(25)
C(26) -C(25)-H(25)
C(25) -C(26) -C(27)
C(25) -C(26) -H(26)
C(27) -C(26) -H(26)
C(26) -C(27)-C(28)
C(26) -C(27) -H(27)
C(28) -C(27) -H(27)
0(2) -C(28) -C(27)
0(2) -C(28) -C(29)
C(27) -C(28) -C(29)
N(2) -C(29) -C(24)
N(2) -C(29) -C(28)
C(24) -C(29) -C(28)
Al-0(3) -C(38)
A1-N(3) -C(31)
A1-N(3) -C(39)
C(31) -N(3) -C(39)
N(3)-C(31) -C(32)
N(3) -C(31) -H(31)
C(32) -C (31) -H(31)
C(31) -C(32) -C(33)
C(31) -C(32) -H(32)
C(33) -C(32) -H(32)
C(32) -C(33) -C(34)
C(32) -C(33) -H (33)
C(34)-C(33) -H(33)
C(33) -C(34) -C(35)
C(33) -C(34) -C(39)
C(35) -C(34) -C(39)
C(34) -C(35) -C(36)
C(34) -C(35) -H(35)
C(36) -C(35) -C(35)
C(35) -C(36) -C(37)
C(35) -C(36) -H(36)
C(37) -C(36)-H(36)
C(36) -C(37) -C(38)
C(36) -C(37) -H(37)
C(38) -C(37) -H(37)
0(3)-C(38)-C(37)
0(3) -C(38) -C(39)
C(37)-C(38) -C(39)
N(3) -C(39) -C(34)
N(3) -C(39)-C(38)
C(34)-C(39)-C(38)


115.2(9)
117.5(9)
120.9(9)
118.2(11)
120.9(13)
119.6(10)
128.4(11)
111.3 (10)
123.4(10)
121.7(11)
114.9(10)
127.7(9)
116.3(8)
116.1(9)
123.3 (8)
114.1(7)
122.7(8)
122.7(8)
133.6(6)
110.2(5)
116.1(7)
122.8(9)
116.9(9)
120.2(10)
102.2(11)
122.5(11)
116.8(11)
120.1(10)
109.8(14)
130.0(14)
127.1(10)
115.8(10)
117.1(10)
122.6(10)
114.0(10)
123.1(11)
120.3 (10)
129.7(10)
109.7(9)
119.9(9)
123.1(9)
116.5(9)
123.9(9)
118.6(8)
117.5(8)
124.9(8)
112.4(7)
122.7(9)


Table 4-10










Table 4-11. Anisotropic Thermal Parameters
Estimated Standard Deviations are given in


Atom U11 U22 U33 U23

Al 41(2) 41(2) 31(2) -3(2)
0(1) 30(4) 59(5) 37(4) 0(3)
N(1) 43(5) 35(5) 34(5) -14(4)
C(11) 62(9) 55(8) 48(8) 11(6)
C(12) 77(10) 59(9) 58(10) -8(7)
C(13) 127(13) 56(9) 41(8) -24(7)
C(14) 99(10) 27(7) 31(7) 2(5)
C(15) 101(10) 70(9) 65(8) 18(7)
C(16) 46(8) 77(10) 100(12) 13(9)
C(17) 51(8) 49(7) 49(8) 16(6)
C(18) 30(7) 41(7) 51(8) 11(6)
C(19) 52(7) 27(6) 43(6) -1(5)
0(2) 27(4) 29(4) 42(4) 8(3)
N(2) 22(5) 33(5) 33(5) 6(4)
C(21) 51(8) 41(8) 36(7) 4(6)
C(22) 46(8) 64(9) 63(8) 6(7)
C(23) 87(10) 30(7) 62(8) -23(6)
C(24) 27(7) 41(7) 43(7) 4(6)
C(25) 71(9) 18(7) 61(8) 4(6)
C(26) 47(7) 46(8) 48(7) -4(7)
C(27) 42(8) 48(8) 41(7) 7(6)
C(28) 25(6) 44(7) 22(6) 10(5)
C(29) 27(5) 32(6) 17(5) 1(4)
0(3) 50(4) 29(4) 28(4) -8(3)
N(3) 41(5) 28(5) 27(5) 3(4)
C(31) 54(8) 45(8) 33(7) -10(6)
C(32) 77(10) 70(10) 35(8) -32(7)
C(33) 34(7) 98(11) 39(7) -24(8)
C(34) 32(7) 53(8) 44(7) -11(7)
C(35) 81(10) 44(8) 49(8) 16(7)
C(36) 55(8) 38(8) 54(8) 24(6)
C(37) 44(7) 35(7) 55(8) 5(6)
C(38) 26(6) 50(8) 31(7) -10(6)
C(39) 21(5) 39(6) 31(6) 1(5)
0(4) 84(7) 93(8) 229(12) -59(8)
C(4) 120(14) 61(16) 270(21) -171(16)


The form or the thermal
U22 + 12c*2U33 + 2klb*c*U23


(A2 x 103) for II.
Parentheses.


U13

5(1)
7(3)
4(4)
15(7)
-7(8)
-16(9)
27(7)
45(8)
48(8)
4(6)
22(5)
15(5)
8(3)
-3(4)
2(6)
33(7)
35(7)
2(5)
-11(7)
13(6)
2(6)
-2(4)
1(4)
1(3)
8(4)
13(6)
22(7)
11(5)
-7(5)
-4(7)
9(6)
2(6)
-4(5)
2(4)
8(7)
85(14)


U12

-1(2)
2(4)
-7(5)
-13(7)
-16(8)
-6(9)
7(7)
-2(8)
13(7)
10(6)
11(6)
3(5)
5(4)
2(4)
-22(7)
-2(7)
0(8)
6(6)
12(7)
12(7)
7(6)
10(6)
-11(5)
-8(4)
10(4)
5(6)
-22(8)
-22(8)
-2(6)
10(8)
5(7)
-14(6)
-1(6)
-5(5)
-6(6)
-71(13)


ellipsoid is exp[-27r2 (h2a*2U1 + k'b*2
+ 2hla*c*U13 + 2hka*b*U12)]









63

angle. For Al(ox)3, the trans bond angles range from 168.30

to 173.90 for an average deviation from ideality of 8.80.

Aluminum-27 NMR Spectroscopy

The Al-27 NMR spectrum for Ia is shown in Figure 4-6.

Two different aluminum environments are present as exhibited

by the two wide peaks on the Al-27 NMR. The first peak is

centered around 54 ppm with a height of 580. The second,

smaller peak is centered around 221 ppm with a height of 160.

An Al-27 NMR study including hexacoordinate aluminum complexes

with aminopolycarboxylic acids reported that chemical shifts

range from 36.5 to 41.2 ppm.57 The complex with one of the

acids investigated by Iyer et al., has been characterized by
























800 600 400 200 0 -200 -400 -600 -800


Figure 4-6. Al-27 NMR Spectrum of the Solid Ia.








64

x-ray crystallography. The aluminum ion in K[Al(EDTA)]*2H20

has been shown to be in a distorted octahedral environment

coordinated to two nitrogen and four oxygen atoms."5 The Al-27

NMR shifts reported for tris complexes of 0,0 bidentate

ligands range from 36 to 41 ppm.17'18 The peak at 54 ppm is

probably due to the aluminum ion surrounded by three nitrogen

and three oxygen atoms in a rather distorted octahedral

environment. Two structures, with the A1N303 confirmed by x-

ray studies, had chemical shifts of 8.1 and 8.2 ppm.27 The

chemical shifts for I and II should be larger than these two

reported studies because environments around the aluminum in

I and II are much more distorted from the ideal octahedral

coordination27. The distorted octahedral environment could be

viewed as approaching a pentacoordinate geometry, which is

generally indicated with chemical shifts near 60 ppm. To

date, there has not been an aluminum complex reported with a

chemical shift near 220 ppm.

The Al-27 NMR spectrum of the solid IIa is shown in

Figure 4-7. There are three different aluminum environments

in the solid sample, as evidenced by the three peaks in the

Al-27 NMR spectrum. Two peaks of almost equal height, 587 and

601, are centered around 5 ppm and 73 ppm, respectively. A

third smaller peak appears centered at -120 ppm.

Solution lib was prepared to separate the mixture. The

Al-27 NMR spectrum of the solution, shown in Figure 4-8, has

only one rather broad peak (W. = 5400 Hz) centered at 54 ppm.





































800 600 o10 200 0 -200 -400 -600 -800


Figure 4-7. Al-27 NMR Spectrum of the Solid IIa.


3SO 300 250 200 1SO 100 50 0 -50 -100 -150


Figure 4-8. Al-27 NMR Spectrum of Al(ox)3 in C2HsOH Solution.









66
Because the structure was confirmed by a second x-ray

analysis, the environment of the aluminum complex in solution

is known to be Al(ox)3 -- a distorted octahedral environment

with three nitrogen and three oxygen atoms. P o s s i b 1 e

explanations for the intermediate peak at 73 ppm in the solid

not directly corresponding to the 54 ppm peak in the solution

include the presence of the solvent molecules and other

complex molecules in the crystal lattice, steric strains due

to packing or solvent effects. Since the location of each

nitrogen and oxygen atom around the aluminum atom has been

verified using x-ray diffraction techniques, the relatively

large value of 54 ppm should be added to the range of chemical

shifts reported for a distorted octahedral environment around

an aluminum ion.

Relatively few compounds with an A1N303 center have been

studied with both x-ray crystallography and Al-27 NMR

spectroscopy. Al (meox) 3 and Al(ox)3 seem to be the least ideal

octahedral aluminum complexes with three nitrogen and three

oxygen atoms to be studied thus far.














CHAPTER 5

ALUMINUM-27 NMR, INFRARED, MASS SPECTROMETRIC AND ELEMENTAL
ANALYSIS OF ALUMINUM COMPLEXES OF N,O DONOR LIGANDS


Introduction


The techniques for the characterization of aluminum

complexes were discussed in Chapter 2. Because suitable

crystals were not produced for compounds III through VII, x-

ray crystallography could not be employed. Therefore, the

remaining methods discussed in Chapter 2 were used to

characterize the synthesized compounds.


Aluminum-27 NMR


Theory

A limited number of aluminum coordination compounds with

nitrogen as a donor atom have been analyzed by Al-27 NMR. The

Al-27 chemical shift is determined by the number and types of

atoms and the symmetry around the aluminum atom.54 The

chemical shifts as well as the donor atoms for some octahedral

environments in aluminum complexes are presented in Table 5-1.

All of the chemical shifts shown are relative to Al(H20)63.

Although shifts near 0 ppm and 80 ppm are generally

produced by octahedral and tetrahedral environments,

respectively, the peaks due to the hexavalent coordination

67










Table 5-1. Al-27 NMR Data and Aluminum Coordination.

Compound 6, ppm N atoms 0 atoms H20 Ref
A1 (H20) 3 (IDA)a 18.2 1 2 3 57
Al(IDA) 2a 36.5 2 4 0 57
A1 (H20) 2 (NTA) b 25.4 1 3 2 57
Al (H20) (HEDTA)c 32.8 2 3 1 57
Al(EDTA)d 41.2 2 4 0 57
A1(PDTA)e 40.7 2 4 0 57
Al(DCTA)f 40.5 2 4 0 57
Al(oz)3g 8.2 3 3 0 27
Al (BrOz) 3 11.4 3 3 0 27
Al(moz) 3 8.1 3 3 0 27
Al(aloz)3j 9.0 3 3 0 27
Al(DTPA) 2-k 37.5 1 5 0 57
Al (pa) 3 39 0 6 0 18
Al(ma)3"' 40 0 6 0 18
Al(mpp)3n 37 0 6 0 17
Al(dpp) 3 36 0 6 0 17

Notes: Ligands are shown in Figure 5-1 a) Iminodiacetic acid,
b)Nitrilotriacetic acid, c) N-(Hydroxyethyl)ethylenediamine-
triacetic acid, d) Ethylenediaminetetraacetic acid, e) 1,2-
Propylenediaminetetraacetic acid, f) trans-1,2-Diamino-
cyclohexanetetraacetic acid, g) 2-(2'-Hydroxyphenyl)-2-
oxazoline, h) 2-(5'-Bromo-2'-hydroxyphenyl)-2-oxazoline,
i) 2-(2'-Hydroxy-3'-methylphenyl)-2-oxazoline, j) 2-(2'-
Hydroxy-3' -allylphenyl)-2-oxazoline, k) Diethylenetriamine-
pentaacetic acid, 1) Pyromeconic acid, m) Maltol, n) 3-
Hydroxy-2-methyl-4-pyridinone, o) 3-Hydroxy-1,2-dimethyl-4-
pyridinone


compounds shown here lie about midway between the two. Also,

the compounds with one or more nitrogen atoms coordinated to

the aluminum are shifted farther than the similar complexes

that contain only oxygen donor atoms. In addition, the more









/CH2COOH
HN\
CH2COOH


CH2COOH
HOOCCH2-N
CH2COOH


HOOCCH2

HNCH2CH2N

HOOCCH2


CH2CH20H



CH2COOH


HOOCCH2

NCH2CH2N
HOOCCH2


CH2COOH


CH2COOH


HOOCCH2 CH2COOH

N-CH-CH2-N

HOOCCH2 CH3 CH2COOH


H --

HO


HOOCCHz /CH2COOH
/N N.
HOOCCH2 CH2COOH


(f)


Br




N

HO


Figure 5-1. Structures of Ligands in Table 5-1.









CHa


(j)

(j)


HOOCCH2


NCH2CH2N


HOOCCH2


HOZ'
CH3
(n)


N
H


CH2COOH

CH2COOH

CH2CH2N

CH2COOH
(k)



0H

HO 0
CH3


HO N" CH3
CH3
(o)


Figure 5-1 -- Continued.








71
water molecules are present in the place of chelating ligands,

the smaller the chemical shift. Because some of the data

reported were for aqueous species without x-ray data, the

precise symmetry of several of the compounds can not be known.

However, it has been reported that the chemical shift for a

distorted octahedral compound will be larger than for one with

an ideal geometry.39 This could explain the smaller chemical

shift when more water molecules are present.

Although not included in this table, the results of the

Al-27 NMR spectra for Al(meox)3 (Ia) and Al(ox)3 (IIa) are

summarized below. In the solid Ia, the main peak appeared at

54 ppm, but there was also a smaller peak at 221 ppm. For the

solid IIa, there were three peaks present. The two larger

peaks, of almost equal height, occurred at 5 and 73 ppm. A

much smaller peak was present at -120 ppm. After IIa was

dissolved in ethanol and left to concentrate by evaporation

(IIb), only one large peak was present at 54 ppm. It should

be noted that the crystals formed from this solution were

characterized by x-ray crystallography and the Al(ox)3

structure confirmed.

Experimental

Compounds III through VII were analyzed in the solid and

solution state using a NT-300 Al-27 NMR spectrophotometer with

spectrometer frequency 78.176839 MHz. The magic-angle

spinning frequency was between 1.1 and 2.4 kHz.









72
Table 5-2. Al-27 NMR Peak Data for Compounds III through VII.


Ligand Compound 6, ppm for solid 6, ppm for
solution
pic III 94 65

-198 15
mpic IV 167 68

-202
-317
pza V 0 70
hyp VI 7 68

74 80
dipic VII 85 68

162
-236


The solutions were prepared by heating the solid in d6-DMSO at

400C to produce clear colorless solutions. The peak data are

summarized in Table 5-2. The spectra are shown in Figures 5-2

through 5-6.

During the synthesis of compound V, the solution

containing pza and the aluminum ion began to turn a pale pink

color as the pH was raised, however, the solid formed is

white. Solutions containing varying aluminum ion to ligand

ratios were prepared by dissolving the appropriate amounts of

pza and Al(N03)3-9H20, followed by the slow addition of solid

NaHCO3 to raise the pH to 5. The solutions were submitted for

Al-27 NMR spectral analysis under the same experimental








































100 ZOO 0 --iOO0 -gO


900


100 0 -100


-so


(b)



Figure 5-2. Al-27 NMR Spectra of III, a) Solid, b) in d6-
DMSO.


am am















































-200 -100


-600 -aOO


200 100 0 -100 -ZOO -S00 PPM


Figure 5-3. Al-27 NMR Spectra of IV, a) Solid, b) in d6-DMSO.


Boo
































o00 600 100 200 0 -20 -100 -600 -o00



(a)























00 1o0 100 0 -'" -s00 -"on nt



(b)


FiQure 5-4. Al-27 NMR Spectra of V, a) Solid, b) in d6-DMSO.






































"00 I 00 I 00 -
600 ;00 qlOg o* 0 -200 -"00 -a,00


Figure 5-5. Al-27 NMR Spectra of VI, a) Solid, b) in d6-DMSO.
































o BOO 100 ZOO 0 -10'0 -C OO -aOm



(a)






















.o0 s 1s00 0a -1o0 -s" o -so


(b)


Figure 5-6. Al-27 NMR Spectra of VII, a) Solid, b) in d.-
DMSO.










Table 5-3. Al-27 NMR Data for Solutions Containing 0.30
and the Tabulated Concentration of pza at pH 5.


78

M A13+


[pza], M shift, ppm rel. ht.
0 M 0 21.8

2 0.3

63 1.0
0.30 M 0 21.7

18 0.3
28 0.1
60 0.1
0.60 M 0 21.8

8 1.3
17 0.5
60 0.1
0.90 M 0 21.8

7 5.6
16 3.6
60 0.1


conditions as all other samples. The data are summarized in

Table 5-3. The spectra are shown in Figures 5-7 through 5-10.

Results

Most of the solid and solution samples produced more than

one peak using Al-27 NMR. It is clear that each of these

contains a mixture of aluminum environments. However, in each

solution, there is a peak near 68 ppm which is rather close to

one of the large peaks, at 73 ppm, in the spectrum of the

solid IIa. This could confirm the presence of a tris aluminum
































140 I2 100 t 0 s 0 o 0 ZO 0 -t -g0 -60



Figure 5-7. Al-27 NMR Spectrum of an
Containing 0.30 M Al3+ at pH 5.


Aqueous Solution


110 IZO 100 sO 80 10 20 0 -20 -to10 -60 -00 -100 -120 PPm


Figure 5-8. Al-27 NMR Spectrum of an Aqueous Solution
Containing 0.30 M A3l and 0.30 M pza at pH 5.



































120 too 00 00 0' 20 0 -20 -o -ma -t -oo -sOG oPI





Figure 5-9. Al-27 NMR Spectrum of an Aqueous Solution
Containing 0.30 M A13+ and 0.60 M pza at pH 5.























S
11 120 100 too 0 10 20 0 -20 -10 -50 -50 -100 -t0 P




Figure 5-10. Al-27 NMR Spectrum of an Aqueous Solution
Containing 0.30 M A3l and 0.90 M pza at pH 5.








81
complex experiencing the same effects as Al(ox)3 between solid

and solution phases. It should be noted that when IIa was

dissolved to form IIb, the only peak present in the Al-27 NMR

spectrum was at 54 ppm. Also, there are no peaks near 70 for

any of the solid samples except for VI with hypoxanthine. It

does not seem likely for the ion [Al(DMSO)6] 3 to be

responsible for these peaks since its chemical shift has been

reported as near 3 ppm.40 The peak at 7 ppm for the solid

sample VI could be a DMSO complex of aluminum.

The Al-27 NMR data confirms the presence of aluminum in

each sample but also suggests the existence of more than one

product for all of the samples except V. Furthermore, since

no coordination compounds have been assigned to the myriad of

chemical shifts present in the spectra, little information can

be gained about the environment of the aluminum ions in the

compounds that have been analyzed.

Compound V, with pyrazinoic acid, has only one peak in

both the solid and solution phases, but these occur at

distinctly different chemical shifts. The solution peak is at

70 ppm similar to the other solutions. The solid, however,

has one peak at 0 ppm, characteristic of Al(H20) 63 or a

perfect octahedral environment. The series of solutions

containing aluminum ion and varying amounts of pza show that

in the absence of the ligand, there are no peaks between

approximately 2 and 60 ppm. The main peak in each spectra is

at 0 ppm, which is most probably due to a large amount of








82
unreacted Al(H2O)63. However, in the spectra for solutions

with the ligand present, peaks near 7, 17 and 28 ppm are

present. These are possibly due to species formed from the

hydrated aluminum ion being involved in a series of pH

dependent equilibria. These equations seem to represent a


A13" + Hpza Al(pza)2' + H+ (1)

Al(pza)2 + Hpza Al(pza)2+ + H (2)

Al(pza) 2 + H20 Al(pza)2(OH) + H+ (3)

Al(pza)2 + Hpza Al(pza)3(s) + H+ (4)


reasonable set of chemical reactions possible in an aqueous

solution with a ligand such as pza. Once the tris complex is

formed, it precipitates and, as a result, only three peaks

other than the hexaaquaaluminum(III) ion should be present.

The series is similar to that proposed for aluminum and

picolinic acid, a ligand of similar reactivity.34 Further

tests or x-ray studies to confirm the structure of the

complexes.


Elemental Analysis

Each of the solid samples were submitted for elemental

analysis. The results are summarized in Table 5-4 as

percentages of carbon, hydrogen and nitrogen present. Also

included are mole ratios, scaled to the number of nitrogen

atoms per ligand molecule, and, at the bottom of the table,








83
Table 5-4. Elemental Analysis Data for Compounds III through
VII and Pure Tris Complexes of the Ligands.


Compound Data type Carbon Hydrogen Nitrogen
III % comp. 48.06 3.08 9.34

ratio 6.00 4.58 1.00
IV % comp. 38.38 3.85 6.90
ratio 6.49 7.75 1.00
V % comp. 26.12 4.30 11.85
ratio 5.15 10.18 2.00
VI % comp. 32.74 3.03 30.90
ratio 4.94 5.49 4.00
VII % comp. 33.84 3.57 5.40

ratio 7.31 9.25 1.00

Al(pic)3 % comp. 54.96 3.08 10.73
Al(mpic)3 % comp. 57.93 4.17 9.65
Al(pza)3 % comp. 45.46 2.29 21.21
Al(hyp)3 % comp. 41.67 2.08 38.89
Al(dipic)3 % comp. 48.01 2.30 8.00


the percentages that would be present if the samples were

unsolvated tris complexes of the ligand.

The data confirms the presence of the ligand in each of

the compounds because the molar ratios of carbon to nitrogen

are, for the most part, very close to those of the ligands.

However, because the amount of hydrogen is high, most likely

due to the presence of water molecules, the molar ratios

involving hydrogen do not correspond to those of the

deprotonated ligands. The percentages for the tris complexes

were included to illustrate the amount of error that would








84

exist due to impurities if the synthesized compounds were the

tris complexes. Furthermore, the Al-27 NMR confirmed the

presence of more than one aluminum environment in all of the

samples except for V. As a result, the elemental percentages

would not match those of any particular compound.


Infrared Spectroscopy


The IR spectra for pic, mpic, pza and dipic and the

sodium salts were prepared on a Perkin-Elmer Fourier Transform

Infrared Spectrophotometer. IR spectra were also taken for

compounds III, IV, V and VII. The data for the carbonyl

stretching frequency in each compound is summarized in Table

5-5. Hypoxanthine was not included because it has no

carboxylic acid group.


Table 5-5. FTIR Carbonyl Peak Data, cm-1.


Unreacted Sodium Disodium Aluminum
Ligand ligand salt salt compound Compound

pic 1715 1584 1672 III
mpic 1677 1587 1683 IV
pza 1713 1612 1678 V
dipic 1693 1634 1618 1610 VII
1731 1666

Each aluminum compound has a carbonyl stretching

frequency between 1660 and 1690 cm-1, between characteristic

carboxylic acid and carboxylate ion regions.52 For III and V,

the single peak occurs between the peaks for the sodium salt








85
and the ligand. This would indicate that in the aluminum

compound, the coordination of the ligand to the metal ion

produces a change in the double bond character that is

distinct from the perturbation caused by the presence of the

sodium near the carboxylate ion. For mpic, the ligand

stretching frequency is lower, probably due to the formation

of an acid dimer.52 However, the peak for IV is near those for

III and V, and, as such, has the ligand coordinated to the

aluminum ion. For VII, there are two peaks present. The peak

at 1666 cm-1 is in the region of the other aluminum compounds

and is, therefore, probably due to a coordinated carboxylate

group. The other peak is close to the one peak for the

disodium dipicolinate salt. The presence of two peaks could

indicate two differently reacting carboxylate groups in one

compound or two compounds with different carboxylate groups.

For the other aluminum compounds, it should be noted that,

despite the presence of more than one aluminum environment,

there is only one visible carbonyl stretching band. Either,

the ligand is coordinated by the same strength bond in every

compound in the mixture or the coordination is so similar that

there is not a distinguishable difference in the carbonyl

stretching frequency.











Fast Atom Bombardment Mass Spectrometry


FABMS were prepared for III, IV, V and VI. Data from

these are given in Table 5-6. Most peaks smaller than ten

percent relative abundance have been omitted.

For III, the sample containing pic, the peak at m/z=204

is possibly due to AlL(H20)3'. There was no peak corresponding

to one ligand molecule, but a peak m/z=79 is probably due to

the ligand fragment left after the loss of carbon dioxide. In

addition, small peaks due to combinations of aluminum, the

ligand and hydroxide were present. The peaks for AlL(OH)2-2

(m/z=181), AlL2(OH)+3 (m/z=291), and AlL3-3(OH) (m/z=342)

appear with m/z=291 being the weakest. Furthermore, a small

peak is present for AlL3+1. It seems likely that the free

ligand would more easily decarboxylate than a coordinated

ligand. Instead the coordinated ligand seems to lose a

hydroxyl group, leaving the coordination sphere intact.

Although the spectrum does support the presence of a tris

complex, the actual proportions of the complexes originally

present would be difficult to determine due to the extensive

fragmentation of the complexes and ligand molecules.

For sample IV, the largest peak corresponds to L+1, with

a decent size fragment due to the decarboxylation of the

ligand. Other prevalent peaks, m/z=166, m/z=299 and m/z=436

are most likely due to complexes such as AlL+3, AlL2, and

A1L3+1, respectively. Although there are many fragments

produced, with the ligand being the greatest in abundance,










Table 5-6. FABMS Peak Data.

Sample III Sample IV Sample V Sample VII

m/z RA* m/z RA* m/z RA* m/z RA*

50 11.14 94 22.08 69 10.06 137 100.0
51 39.43 120 28.28 81 2.44 138 16.75
52 12.82 138 100.0 107 21.99 165 25.96
63 11.26 139 40.00 125 100.0 177 19.65
77 26.99 166 51.92 138 33.78 273 32.53
78 14.36 167 15.72 153 11.64 301 1.95
79 24.66 178 46.24 165 13.03 313 1.41
130 11.53 213 52.48 187 13.34 391 0.04
131 16.82 214 11.52 397 1.06
159 36.97 257 43.12
181 57.88 299 10.64
203 29.60 436 15.16
204 100.0
291 0.15
326 61.85
327 46.16
342 59.59
343 17.48
362 70.88
363 16.01
394 0.11

* RA stands for the percent relative abundance.


the original sample contained a fair percentage of the tris

complex.

With only a few peaks at large masses, the spectrum for

compound V, containing pza, does not provide much detail about

the ratios of complexes present in the original sample.

Although the ligand was the most prevalent ion, it is apparent

by the peaks at m/z=107 and m/z=81 that the ligand decomposed

by losing small fragments such as H20 and C02. The small peak

at m/z=397 is most probably due to AlL3+1. One other small

peak at m/z=187, which could be due to AlL(OH)2+3 or A1L2-2CO2,

seems to be the only other indication of an aluminum complex.








88

The spectrum of VI, with the largest peak (m/z=137)

corresponding to L+1, does not provide much information on the

relative amounts of complexes present in the sample. The

remaining large peaks, m/z=165, m/z=177, and m/z=273, are

probably due to AlL+3, AIL(OH)-2 and 2HL+1, respectively. Two

of the smaller peaks, m/z=301 and m/z=313, are probably due to

AlL2+4 and AlL2(OH)-1. There is no peak present near m/z=432,

where AlL3 would be. The nearest peak, m/z=391, is smaller by

41 units. It seems reasonable that one ring is a complex

could have fragmented. The small peak at M-43 could be due to

the loss of part of one of the rings. By a similar

fragmentation, any AlL3 that could have been present may have

been responsible for this peak.


Conclusion


The structure of the compounds III through VII can not be

determined from the data provided by the three techniques

discussed in this chapter. Without more thorough calibration

of the Al-27 NMR scale, the available data merely confirms the

presence of the aluminum ion in more than one possible

environment in a single sample. In addition, without a pure

sample, elemental analysis provides little information beyond

the confirmation of the ligand's presence. Finally, the

carbonyl stretching frequency data confirms the coordination

of the aluminum ion to the ligand yet does not provide any

further information. Without the use of x-ray




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