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Synthesis and Investigation of New Organoplatinum Complexes and Kinetic Isotope Effect in Organoplatinum(II) Oxidative Addition Reactions

Ph. D. DISSERTATION IN

INORGANIC CHEMISTRY

Synthesis and Investigation of New Organoplatinum Complexes

and

Kinetic Isotope Effect in Organoplatinum(II)

Oxidative Addition Reactions

ABSTRACT

In part I, the secondary α-deuterium kinetic isotope effects (KIEs), (k_H/k_D)_α, have been determined, at different temperatures and in solvents having different polarities, for reaction of PhCH₂Br/PhCD₂Br with the dimethylplatinum(II) complexes [PtMe₂(NN)], in which the bidentate NN ligand is bpy (= 2,2′-bipyridine) or bu₂bpy (= 4,4′-di-tert-butyl-2,2′-bipyridine). The values obtained for the secondary α-deuterium KIEs in acetone solution are close to 1 and may be normal or inverse, but much larger values are found for the reactions in benzene. An explanation is presented on the basis of solvent dependence of the degree of looseness of the transition state in the S_N2 mechanism.

In part II, the substitution reactions of the labile SMe₂ ligand in the cycloplatinated(II) complexes [PtR(ppy)(SMe₂)], 1, in which ppy = 2-phenylpyridinate and R = Me, 1A, or p-MeC₆H₄, 1B, by pyridine-2-thione, C₅H₅SN, were studied. When each of the complexes 1 was treated with 1 equiv C₅H₅SN, existing as a mixture of tautomers thiol (N^SH) and thione (HN^S), a mixture containing the S-bound thiol complex [PtR(ppy)(η¹–S-S^NH)] (R = Me, 2A, or R = p-MeC₆H₄, 2B) and the dimeric complex [Pt(ppy)(N^S)]₂, 3, having two bridging deprotonated pyridine-2-thione (N^S) ligands, was observed along with the evolution of free R-H. This mixture was finally led to pure complex 3 after 3 days. Pure samples of the complexes 2A and 3 were obtained from the above mentioned 2A+3 mixtures by using flash chromatography on silica gel. Kinetics of the reactions were investigated by UV-vis spectroscopy (complexes 1 have a MLCT band in the visible region which was used to easily follow the reactions) and ¹H-NMR spectroscopy. On the basis of the results, a mechanism was proposed for the related reactions.

Key words: Oxidative Addition, Kinetic, Isotope Effects, pyridine-2-thione.

دسته: زبان خارجه, زبان خارجه برچسب: Isotope Effects, Key words: Oxidative Addition, Kinetic, pyridine-2-thione.

توضیحات

LIST OF CONTENTS

Content Page

Chapter One:Introduction and Literature Review

1.1. General Survey on Organometallic Chemistry. 1

1.2. Organoplatinum Complexes. 3

1.3. Fundamental Organometallic Reactions. 3

1.3.1. Oxidative Addition: General Considerations. 4

1.3.1.1. Mechanisms of Oxidative Addition. 5

1.3.1.1.1. Three-center Concerted Additions. 5

1.3.1.1.2. Nucleophilic (SN2) Reactions. 6

1.3.1.1.3. Radical Mechanisms. 7

1.3.1.1.4. Ionic Mechanisms. 8

1.3.1.1.5. Sigma-bond Metathesis Mechanisms. 9

1.4. Kinetic Isotope Effect 10

1.4.1. Basis of KIE.. 11

1.4.2. Origin of Isotope Effects. 12

1.4.3. Magnitude of the Observed KIEs. 14

1.4.3.1. Primary Isotope Effects. 15

1.4.3.2. Secondary Isotope Effects. 16

1.4.3.2.1. α-Secondary Kinetic Isotope Effects. 16

1.4.3.2.2. β-Secondary Kinetic Isotope Effects. 21

1.4.4. Equilibrium Isotope Effects. 22

1.4.5. Solvent Isotope Effects. 23

1.5. Substitution Reactions. 24

1.6. Hemilabile Ligands. 26

1.7. Complexes of Hetrocyclic Thione Donors. 27

1.7.1. General Aspects of Heterocyclic Thione Donors. 28

1.7.1.1. Heterocyclic Thionates as Monodentate Ligands. 30

1.7.1.2. Heterocyclic Thionates as Chelating Ligands. 32

1.7.1.3. Heterocyclic Thionates as Bridging Ligands. 34

1.7.2. Binuclear Complexes Containing Heteroyclic Thionates. 37

Chapter Two: Experimental

2.1. Source of Chemicals. 42

2.2. Techniques and Methods. 42

2.2.1. Inert Atmosphere Techniques. 42

2.2.2. ¹H-NMR Spectroscopy. 42

2.2.3. ¹³C{¹H}-NMR Spectroscopy. 43

2.2.4. Microanalysis. 43

2.2.5. IR Spectroscopy. 43

2.2.6. UV-Visible Spectroscopy. 43

2.2.7. Determination of Melting Points. 43

2.2.8. Preparation of Dry Ether 44

2.3. Preparation of Starting Compounds. 44

2.3.1. Preparation of K₂PtCl₆ 44

2.3.1.1. Preparation of K₂PtCl₆ from Laboratory Platinum Residual 44

2.3.1.2. Preparation of K₂PtCl₆ from Pure Platinum Metal 45

2.3.2. Preparation of K₂PtCl₄ 45

2.3.3. Preparation of cis/trans-[PtCl₂(SMe₂)₂] 46

2.3.4. Preparation of [Me₂Pt(µ-SMe₂)₂PtMe₂] 46

2.3.5. Preparation of para-Tolyllithium Solution. 47

2.3.6. Preparation of cis-[Pt(p-MeC₆H₄)₂(SMe₂)₂] 47

2.3.7. Preparation of cis-[Pt(Cl)₂(dmso)₂] 48

2.4. Synthesis of Platinum(II) Complexes Containing Aromatic Nitrogen-Donor Ligands 48

2.4.1. Preparation of [PtMe₂(bpy)], 1a. 48

2.4.2. Preparation of [PtMe₂(bu₂bpy)], 1b. 49

2.4.3. Preparation of [PtMe₂(Me₂bpy)], 1c. 49

2.5. Synthesis of Platinum(IV) Complexes Containing Aromatic Nitrogen-Donor Ligands 50

2.5.1. Preparation of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a. 50

2.5.2. Preparation of trans-[PtBr(CD₂Ph)Me₂(bpy)], 2a*. 50

2.5.3. Preparation of trans-[PtBr(CH₂Ph)Me₂(bu₂bpy)], 2b. 51

2.5.4. Preparation of trans-[PtBr(CD₂Ph)Me₂(bu₂bpy)], 2b*. 51

2.5.5. Preparation of trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c. 52

2.5.6. Preparation of trans-[PtBr(CD₂Ph)Me₂(Me₂bpy)], 2c*. 52

2.6. Kinetic Study. 53

2.7. KIEs by Competition Experiments. 53

2.8. Synthesis of Platinum(II) Complexes Containing Cyclometalated 2-Phenylpyridine, (ppy), Ligand. 54

2.8.1. Preparation of [PtMe(ppy)(SMe₂)], 1A.. 54

2.8.2. Preparation of [Pt(p-MeC₆H₄)(ppy)(SMe₂)], 1B.. 54

2.8.3. Preparation of [Pt(dmso)(ppy)(Cl)], 1C.. 55

2.9. Synthesis of Platinum(II) Complexes Containing Pyridine-2-thione (S^NH) and Cyclometalated 2-Phenylpyridine, (ppy), Ligands. 55

2.9.1. Reaction of [PtMe(ppy)(SMe₂)], 1A, with C₅H₅SN.. 55

2.9.1.1. [PtMe(ppy)(η¹–S-S^NH)], 2A.. 56

2.9.1.2. [Pt(ppy)(N^S)]₂, 3. 56

2.9.2. Reaction of [Pt(p-MeC₆H₄)(ppy)(SMe₂)], 1B, with C₅H₅SN.. 57

2.9.3. Direct Preparation of [Pt(ppy)(N^S)]₂, 3. 58

2.9.4. Monitoring the Reaction of 1A with C₅H₅SN by ¹H-NMR Spectroscopy. 58

2.9.5. Monitoring the Reaction of 1B with C₅H₅SN by ¹H-NMR Spectroscopy. 59

2.9.6. Kinetic Study (Part II) 59

2.9.7. Theoretical Methods. 59

2.9.8. X-Ray Crystal Structure Determination. 59

Chapter Three:Results and Discussion

3.1.1. General Remarks about NMR Spectroscopy of Organoplatinum Complexes. 62

3.1.2. Part I: Secondary Kinetic Isotope Effects in Oxidative Addition of Benzyl 65

3.1.3. Synthesis and Characterization of Precursor Complexes. 65

3.1.3.1. cis/trans– [PtCl₂(SMe₂)₂] 65

3.1.3.1.1. ¹H-NMR spectrum of cis/trans-[PtCl₂(SMe₂)₂] 66

3.1.3.2. [Me₂Pt(µ-SMe₂)₂PtMe₂] 68

3.1.3.2.1.¹H-NMR spectrum of [Me₂Pt(µ-SMe₂)₂PtMe₂] 68

3.1.3.3. [PtMe₂(bpy)], 1a. 70

3.1.3.3.1.¹H-NMR spectrum of [PtMe₂(bpy)], 1a. 70

3.1.3.4. [PtMe₂(bu₂bpy)], 1b. 72

3.1.3.4.1.¹H-NMR spectrum of [PtMe₂(bu₂bpy)], 1b. 72

3.1.3.5. [PtMe₂(Me₂bpy)], 1c. 74

3.1.3.5.1.¹H-NMR spectrum of [PtMe₂(Me₂bpy)], 1c. 74

3.1.4. Synthesis and Characterization of Platinum(IV) Complexes Containing Aromatic Nitrogen-Donor Ligands. 76

3.1.4.1. trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a. 76

3.1.4.1.2. ¹H-NMR Spectrum of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a. 77

3.1.4.1.3. ¹³C{¹H}-NMR Spectrum of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a. 79

3.1.4.1.4. ¹³C{¹H}-DEPT-NMR Spectrum of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a. 81

3.1.4.2. [PtBr(CD₂Ph)Me₂(bpy)], 2a*. 82

3.1.4.2.1. ¹H- NMR Spectrum of trans-[PtBr(CD₂Ph)Me₂(bpy)], 2a*. 82

3.1.4.3. trans-[PtBr(CH₂Ph)Me₂(bu₂bpy)], 2b. 84

3.1.4.3.1. Elemental Analysis of trans-[PtBr(CH₂Ph)Me₂(bu₂bpy)], 2b. 84

3.1.4.3.2. ¹H-NMR Spectrum of [PtBr(CH₂Ph)Me₂(bu₂bpy)], 2b. 85

3.1.4.3.3. ¹³C{¹H}-NMR Spectrum of [PtBr(CH₂Ph)Me₂(bu₂bpy)], 2b. 87

3.1.4.4. trans-[PtBr(CD₂Ph)Me₂(bu₂bpy)], 2b*. 89

3.1.4.4.1. ¹H- NMR Spectrum of trans-[PtBr(CD₂Ph)Me₂(bu₂bpy)], 2b*. 89

3.1.4.5. trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c. 90

3.1.4.5.1 Elemental Analysis of trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c. 90

3.1.4.5.2. ¹H-NMR spectrum of trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c. 91

3.1.4.5.3. ¹³C{¹H}-NMR Spectrum of trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c. 93

3.1.4.5.4. ¹³C{¹H}-DEPT-NMR Spectrum of trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c 93

3.1.4.6. trans-[PtBr(CD₂Ph)Me₂(Me₂bpy)], 2c*. 93

3.1.5. Kinetic and Mechanistic Studies of Oxidative Addition Reaction of Benzyl 96

3.1.5.1. General Remarks. 96

3.1.5.2. Second Order Reactions. 96

3.1.6. KIEs by Competition Experiments. 103

3.1.7. DFT calculations. 108

3.1.8. Conclusions. 112

3.2. Part II: C-H Reductive Elimination During the Reaction of Cycloplatinated(II) Complexes with Pyridine-2-thione: Kinetic Follow up. 114

3.2.1. Synthesis of Precursor Complexes. 115

3.2.1.1. cis-[Pt(p-MeC₆H₄)₂(SMe₂)₂] 115

3.2.1.1.1. ¹H-NMR of cis-[Pt(p-MeC₆H₄)₂(SMe₂)₂] 115

3.2.1.2. [PtCl₂(dmso)₂] 117

3.2.2. Synthesis of Platinum(II) Complexes Containing Cyclometalated 2-Phenylpyridine Ligand 119

3.2.2.1. [Pt(Me)(ppy)(SMe₂)], 1A.. 119

3.2.2.1.1. ¹H-NMR of [Pt(Me)(ppy)(SMe₂)], 1A.. 119

3.2.2.2. [Pt(p-MeC₆H₄)(ppy)(SMe₂)], 1B.. 121

3.2.2.2.1. ¹H-NMR of [Pt(p-MeC₆H₄)(ppy)(SMe₂)], 1B.. 121

3.2.2.3. [Pt(ppy)Cl(dmso)], 1C.. 123

3.2.3. Synthesis of Platinum(II) Complexes Containing Pyridine-2-thione and Cyclometalated 2-Phenylpyridine Ligands. 125

3.2.3.1. Reaction of [PtMe(ppy)(SMe₂)], 1A, with C₅H₅SN.. 125

3.2.3.2. [PtMe(ppy)(η¹–S-S^NH)], 2A.. 126

3.2.3.2.2. ¹H-NMR Spectrum of [PtMe(ppy)(η¹–S-S^NH)], 2A.. 127

3.2.3.2.3. IR Spectrum of [PtMe(ppy)(η¹–S-S^NH)], 2A.. 129

3.2.3.3. [Pt(ppy)(N^S)]₂, 3. 130

3.2.3.3.1. Elemental Analysis of [Pt(ppy)(N^S)]₂, 3. 130

3.2.3.3.2. ¹H -NMR Spectrum of [Pt(ppy)(N^S)]₂, 3. 130

3.2.3.3.3. Crystal Structure of [Pt(ppy)(N^S)]₂, 3. 131

3.2.3.4. Reaction of [Pt(p-MeC₆H₄)(ppy)(SMe₂)], 1B, with C₅H₅SN.. 133

3.2.3.4.1. ¹H-NMR Spectrum of the Mixture of [Pt(p-MeC₆H₄)(ppy)(η¹–S-S^NH)], 2B and [Pt(ppy)(N^S)]₂, 3. 133

3.2.3.5. Direct Preparation of [Pt(ppy)(N^S)]₂, 3. 136

3.2.3.5.1. ¹H-NMR Spectrum of [Pt(ppy)(N^S)]₂, 3. 136

3.2.4. Kinetics and Mechanism of the Reactions. 138

3.2.4.1. Kinetic studies by UV-vis Spectroscopy. 139

3.2.5. Monitoring the Reactions of [PtMe(ppy)(SMe₂)], 1A with Pyridine-2-thione by ¹H-NMR Spectroscopy. 145

3.2.6. Monitoring the Reactions of [Pt(p-MeC₆H₄)(ppy)(SMe₂)], 1B with Pyridine-2-thione by ¹H-NMR Spectroscopy. 148

3.2.7. Geometry Optimizations. 150

3.2.7.1. Energy Profile for the Product Formation. 152

References. 157

LIST OF FIGURE

Content Page

Figure 1-1. Morse potential diagram for C-H and C-D bonds. 13

Figure 1-2. The reaction coordinate diagram for a typical primary H/D KIE. 14

Figure 1-3. Some examples of primary kinetic isotope effects. 15

Figure 1-4: The reaction coordinate diagram for the secondary α-deuterium KIE. (C-H/C-D bonds are not being broken during the process, but the carbon atoms experience an sp³ to sp² hybridization change.)⁵⁸ 17

Figure 1-5. The reaction coordinate diagram for the secondary α-deuterium KIE. (C-H/C-D bonds are not being broken during the process, but the carbon atoms experience an sp² to sp³ hybridization change.)⁵⁸ 18

Figure 1-6. The C-H(D) out-of-plane bending vibrations in the substrate and in the S_N1 and S_N2 transition states. 19

Figure1-7. The relationship between the looseness (the nucleophile-leaving group distance) of the S_N2 transition state and the magnitude of the secondary α-deuterium KIE as determined by the C_α-H(D) out-of-plane bending vibtrations in the transition state. 20

Figure 1-8. Some examples of α-secondary kinetic isotope effects.^63-64 21

Figure 1-9. Some examples of β-secondary kinetic isotope effects. 21

Figure 1-10. The reactions coordinate diagrams for typical EIEs. 23

Figure 1-11. Heterocyclic thionates that most frequently involved as bridging ligands. 35

Figure 1-12. (a) µ₂-S(η²-S), (b) µ₂-S,N(η¹-S; η¹-N), (c) µ₂-S,N(η²-S; η¹-N), (d) µ₃-S,N(η¹-S; η¹-N), (d) µ₃-S,N(η²-S; η¹-N), (e) µ₄-S,N(η³-S; η¹-N), (f) µ₃(η³-S). 36

Figure 1-13. Conversion between µ₂-S,N (a) and µ₂-S(η²-S) (b) bridging modes, Among binuclear heterocyclic thionate containing complexes. 37

Figure 3-1. ¹H-NMR spectrum (250 MHz) of a mixture of cis/trans-[PtCl₂(SMe₂)₂] in CDCl₃. 67

Figure 3-2. ¹H-NMR spectrum (250 MHz) of [Me₂Pt(µ-SMe₂)₂PtMe₂] in CDCl₃. 69

Figure 3-3. ¹H-NMR spectrum (250 MHz) of [PtMe₂(bpy)], 1a, in CDCl₃. 71

Figure 3-4. ¹H-NMR spectrum (250 MHz) of [PtMe₂(bu₂bpy)], 1b, in CDCl₃. 73

Figure 3-5. ¹H-NMR spectrum (250 MHz) of [PtMe₂(Me₂bpy)],1c, in CDCl₃. 75

Figure 3-6. ¹H-NMR spectrum (400 MHz) of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a, in CDCl₃. 78

Figure 3-7. Expansion of aromatic region between 6.0- 8.8 ppm of the ¹H-NMR spectrum (400 MHz) of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a, in CDCl₃. 79

Figure 3-8. ¹³C{¹H}-NMR spectrum (201 MHz) of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a, in CDCl₃. 80

Figure 3-9.¹³C{¹H}-DEPT-NMR spectrum (201 MHz) of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a, in CDCl₃. 81

Figure 3-10. ¹H-NMR spectrum (250 MHz) of [PtBr(CD₂Ph)Me₂(bpy)], 2a*, in CDCl₃. 83

Figure 3-11.¹H-NMR spectrum (400 MHz) of trans-[PtBr(CH₂Ph)Me₂(bu₂bpy)], 2b, in CDCl₃. 86

Figure 3-12. Expansion of aromatic region between 6.0- 8.8 ppm of the ¹H-NMR spectrum (400 MHz) of trans-[PtBr(CH₂Ph)Me₂(bu₂bpy)], 2b, in CDCl₃. 87

Figure 3-13. ¹³C{H}-NMR spectrum (201 MHz) of trans-[PtBr(CH₂Ph)Me₂(bu₂bpy)], 2b, in CDCl₃. 88

Figure 3-14.¹H-NMR spectrum (400 MHz) of trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c, in CDCl₃. 92

Figure 3-15: ¹³C{¹H}-NMR spectrum (202 MHz) of trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c, in CDCl₃. 94

Figure 3-16:¹³C{¹H}-DEPT-NMR spectrum (202 MHz) of trans-[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c, in CDCl₃. 95

Figure 3-17. Changes in the UV-visible spectrum during the reaction of [PtMe₂(bpy)], 1a (3 mL of 3×10^-4 M solution), with PhCH₂Br, under second-order 1:1 stoichiometric conditions, in acetone at 25°C: (a) initial spectrum (before adding PhCH₂Br); (b) spectrum at t = 0; successive spectra recorded at intervals of 30 s. 99

Figure 3-18. Changes in the UV-visible spectrum during the reaction of [PtMe₂(bpy)], 1a (3 mL of 3×10^-4 M solution), with PhCH₂Br, under second-order 1:1 stoichiometric conditions, in benzene at 25°C: (a) initial spectrum (before adding PhCH₂Br); (b) spectrum at t = 0; successive spectra recorded at intervals of 1 min. 99

Figure 3-19. Absorbance-time curves for the reaction of [PtMe₂(bpy)] with PhCH₂Br, in 1:1 stoichiometric condition, in acetone at different temperatures 15, 20, 25, 30, 35 ºC (increases reading downward) . 100

Figure 3-20. Absorbance-time curves for the reaction of [PtMe₂(bu₂bpy)] with PhCH₂Br, in 1:1 stoichiometric condition, in acetone at different temperatures 15, 20, 25, 30ºC (increases reading downward) . 100

Figure 3-21. Eyring plots for the reactions with PhCH₂Br in acetone: (a) for complex 1a; (b) for complex 1b. 101

Figure 3-22. Eyring plots for the reactions with PhCD₂Br in acetone: (a) for complex 1a; (b) for complex 1b. 101

Figure 3-23. ¹H-NMR spectra in CDCl₃ of (A) trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a, (B) mixture of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a, and trans-[PtBr(CD₂Ph)Me₂(bpy)], 2a, (C) trans-[PtBr(CD₂Ph)Me₂(bpy)], 2a. 105

Figure 3-24. Proposed initiation of the S_N2 oxidative addition. 108

Figure 3-25. Calculated structures and relative energies (kJ mol^-1) for product 2a, intermediate A1 and transition states B1 and C1, arising from the reaction of 1a + PhCH₂Br + acetone (E = 0) in acetone solution. 110

Figure 3-26. ¹H-NMR spectrum (250 MHz) of cis-[Pt(p-MeC₆H₄)₂(SMe₂)₂] in CDCl₃. 116

Figure 3-27. ¹H-NMR spectrum (400 MHz) of cis-[PtCl₂(dmso)₂] in acetone-d₆. 118

Figure 3-28. ¹H-NMR spectrum (250MHz), of [Pt(Me)(ppy)(SMe₂)], 1A, in CD₂Cl₂. 120

Figure 3-29. ¹H-NMR spectrum of [Pt(p-MeC₆H₄)(ppy)(SMe₂)], 1B, in CD₂Cl₂. 122

Figure 3-30. ¹H-NMR (250 MHz) spectrum of [Pt(ppy)Cl(dmso)], 1C, in CDCl₃. 124

Figure 3-31. ¹H-NMR spectrum (250 MHz) of [PtMe(ppy)(η¹–S-S^NH)], 2A, in CDCl₃. 128

Figure 3-33. Crystal structure of complex 3 from crystallization of the product obtained from mixing of complex 1A and C₅H₅SN. The H atoms are omitted for clarity. 131

Figure 3-34. ¹H-NMR spectrum (250 MHz), of [Pt(ppy)(N^S)]_2,3, in CDCl₃. 132

Figure 3-35. ¹H-NMR spectrum of the mixture of [Pt(p-MeC₆H₄)(ppy)(η¹–S-S^NH)], 2B, and [Pt(ppy)(N^S)]₂, 3, in CDCl₃. 135

Figure 3-36. ¹H-NMR spectrum (400 MHz), of [Pt(ppy)(N^S)]₂,in DMSO-d₆. 137

Figure 3-37. Absorbance-wave lenght curve for complex 3. 140

Figure 3-38. The changes in the UV-vis spectrum during the reaction of [Pt(p-MeC₆H₄)(ppy)(SMe₂)], 1B, with pyridine-2-thione (each 3 × 10^-4 M) in CH₂Cl₂at 25 °C: (a) pure 1B; (b) pure pyridine-2-thione; (c) spectrum at t = 0; successive spectra recorded at intervals of 1 min. 141

Figure 3-39.The changes in the UV-vis spectrum during the reaction of [Pt(Me)(ppy)(SMe₂)], 1A, with 2-mercaptopyridine. (a) pure 1A; (b) spectrum at = 0; successive spectra recorded at intervals of 1 min. 141

Figure 3-40. Absorbance (at 500 nm)-time curves for the reaction of [Pt(p- MeC₆H₄)(ppy)(SMe₂)], 1B, with pyridine-2-thione, using 1:1 stoichiometry, in CH₂Cl₂at temperatures of 15, 20, 25, 30 and 35 °C (temperature increases reading upward). 142

Figure 3-41. Absorbance (at 500 nm)-time curves for the reaction of [Pt(Me)(ppy)(SMe₂)], 1A, with pyridine-2-thione, using 1:1 stoichiometry, in CH₂Cl₂at temperatures of 10, 20, 25, 30 and 35 °C (temperature increases reading upward). 142

Figure 3-42. Eyring plots for reductive elimination of R-H and formation of dimer 3 from (a) complex 2A’ (R = Me) and (b) 2B’ (R = p-MeC₆H₄) in CH₂Cl₂. 143

Table 3-13. Rate constants^a and activation parameters for R-H reductive elimination from the complexes 2A’ or 2B’ to give dimer 3 in CH₂Cl₂ solution. 144

Figure 3-43. ¹H-NMR spectra of reaction of complex 1A, with pyridine-2-thione at 27 °C in C₆D₆; (a) pure 1A, (b) immediately after addition of pyridine-2-thione to 1A, (c) 5 min after addition, (d) 10 min after addition, (e) 15 min after addition, (f) 20 min after addition, (g) 30 min after addition, (h) 60 min after addition, (i) 90 min after addition, (j) 120 min after addition, (k) 150 min after addition, (l) 180 min after addition, (m) 300 min after addition , (n) 330 min after addition, (o) 24 h after addition . Signals with satellites are assigned to complex 1A, 2A’ and complex 2A. 147

Figure 3-44. ¹H-NMR spectra (aliphatic region) of reaction of complex 1B, with pyridine-2-thione at 27 °C in CD₂Cl₂; (a) pure 1B, (b) immediately after addition of pyridine-2-thione to 1B, (c) 20 min after addition, (d) 60 min after addition, (e) 120 min after addition, (f) 5h after addition,. 149

Figure 3-45. DFT optimized structures of complexes 2A, 2B and 3. The H atoms (except H of S^NH ligand) are omitted for clarity. 150

Figure 3-46. Calculated structures and relative energies of species involved in the reaction of complex 1A with pyridine-2-thione. 153

Figure 3-47. Calculated structures and relative energies of species involved in the reaction of complex 1B with pyridine-2-thione. 154

LIST OF TABLE

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Table 2-1. λ_max’s of [PtMe₂(NN)] complexes in acetone and benzene. 53

Table 2-2. Crystal data and structure refinement for [Pt(ppy)(N^S)]₂, 3. 60

Table 3-1: Elemental Analysis of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2a. 76

Table 3-2. Elemental Analysis of trans-[PtBr(CH₂Ph)Me₂(bpy)], 2b. 84

Table 3-3. Elemental Analysis of trans –[PtBr(CH₂Ph)Me₂(Me₂bpy)], 2c. 90

Table 3-4. λ_max’s of [PtMe₂(NN)] complexes in acetone or benzene. 98

Table 3-5. Rate constants, activation parameters, and kinetic α-deuterium isotope effects for the reaction of complex [PtMe₂(bpy)], 1a, with C₇H₇Br /C₇H₅D₂Br in acetone or benzene. 102

Table 3-6. Rate constants, activation parameters, and kinetic α-deuterium isotope effects for the reaction of complex [PtMe₂(bu₂bpy)], 2b, with C₇H₇Br /C₇H₅D₂Br in acetone or benzene. 103

Table 3-7. Kinetic α-deuterium isotope effects from Uv-vis spectroscopy and kinetic α-deuterium isotope effects from NMR product analysis, for the reaction of complexes [PtMe₂(bpy)] (1a) or [PtMe₂(bu₂bpy)] (1b) with PhCH₂Br/PhCD₂Br in acetone or benzene. 104

Table 3-8. Secondary α-deuterium kinetic isotope effects for the reaction of complex [PtMe₂(bpy)], 1a, in acetone or benzene. 106

Table 3-9. Secondary α-deuterium kinetic ksotope effects for nucleophilic substitution reactions of benzyl derivatives. 107

Table 3-10. Calculated Hirshfeld atomic charges and selected distances (Å) for the compounds of Scheme 3-4. 112

Table 3-11: Elemental Analysis of [PtMe(ppy)(η¹–S-S^NH)], 2A. 126

Figure 3-32. IR Spectrum of [PtMe(ppy)(η¹–S-S^NH)], 2A. 129

Table 3-12. Elemental Analysis of [Pt(ppy)(N^S)]₂, 3. 130

Table 3-14. Selected calculated bond distance (Å) and angle () for complexes 2, and 3. 152

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