Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes

Home , Aziridines, Nitrene, Scorpionate ligand, Sulfonamide

A dissertation presented to

the faculty of

the College of Arts and Sciences of Ohio University

In partial fulfillment

of the requirements for the degree

Doctor of Philosophy

Shengwen Liang

August 2012

This dissertation titled

Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes

SHENGWEN LIANG

has been approved for

the Department of Chemistry and Biochemistry

and the College of Arts and Sciences by

Michael P. Jensen

Associate Professor of Chemistry

Howard Dewald

Interim Dean, College of Arts and Sciences 3

ABSTRACT

LIANG, SHENGWEN, Ph.D., August 2012, Chemistry

Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes

Director of Dissertation: Michael P. Jensen

Transition metal catalyzed C=C bond aziridination and C-H bond amination reactions are powerful synthetic methods for forming C-N bonds directly from unfunctionalized hydrocarbons, and have enormous synthetic potential in chemical processes leading to natural products, pharmaceuticals and materials. Catalytic C-H bond amination also offers a way to achieve functionalization with clean and environmentally sustainable atom efficiency.

This work will focus on olefin aziridinations and C-H bond aminations catalyzed by transition metal complexes. We employed N 3-tripod scorpionate ligands to support different transition metal centers. Therefore, complexes [(L)M(NCCH 3)3](BF 4)n (L =

tris{3,5-dimethylpyrazol-1-yl}methane, Tpm Me,Me , M = Mn, Fe, Co, Ni, n = 2; L = tris{3-

phenylpyrazol-1-yl}methane, Tpm Ph , M = Mn, Fe, Co, Ni, n = 2; L = hydrotris{3,5-

dimethylpyrazol-1-yl}borate, Tp Me,Me , M = Fe, Co, Ni, n = 1; L = hydrotris{3-phenyl-5- methylpyrazol-1-yl}borate, Tp Ph,Me , M = Mn, Co, Fe, Ni, n = 1) were prepared and

characterized. These complexes were utilized as metal catalysts for nitrene transfer from

phenyl-N-tosyliminoiodinane (i.e., PhI=NTs) to variety of organic substrates, resulting in

olefin aziridination and C-H bond amination with varying degrees of efficiency. A wide

range of organic products was obtained and fully characterized, and reaction mechanisms

were probed with Hammett and kinetic isotope effects. Meanwhile, a masked Lewis acid 4

[Fe(NCMe) 6](BF 4)2 was found to catalyze [2+1+2] and [3+2] cycloaddition reactions, leading to the formation of various five-membered nitrogen-containing compounds.

Approved: ______

Michael P. Jensen

Associate Professor of Chemistry

To My Parents Xiuzhen Qiu and Guoping Liang

ACKNOWLEDGMENTS

This dissertation, and all of my research work at Ohio University, would not have been possible without the time and support of quite a few people. I need to begin with thanking my advisor Prof. Michael P. Jensen for giving me the opportunity to work in his laboratory on such an interesting research project. He has been a wonderful mentor offering me patience and guidance throughout the past five years. It seems to me that I gain valuable lessons not only on chemistry but also on scientific method, logic, and interpersonal relationships that would be valuable for my future career.

In addition, I would like to thank the members of my committee, Prof. Jeffrey J.

Rack, Prof. Hao Chen and Prof. R. Guy Riefler. Prof. Rack in particular has been a valuable source of knowledge for my research.

I would like to thank Prof. Jeffrey L. Petersen at West Virginia University and Dr.

Victor G. Young, Jr. at University of Minnesota for solving the crystal structures. And I also would like to thank Prof. Stephen C. Bergmeier and his graduate student Fang Fang for the valuable discussion about nitrene chemistry.

Also, I want to thank my labmates, faculty and staff from the Department of

Chemistry and Biochemistry, my research work has become much easier with generous support from these people.

Last but not least, I would like to thank my deeply loved parents Xiuzhen Qiu and

Guoping Liang, who have given me the support and encouragement to complete my

Ph.D. in chemistry. 7

TABLE OF CONTENTS Page

Abstract ...... 3 Dedication ...... 5 Acknowledgments...... 6 List of Tables ...... 10 List of Figures ...... 12 List of Schemes ...... 15 Chapter 1: Introduction ...... 17 General Aspects ...... 17 C-H Bond Amination Reactions ...... 20 Aziridination of C=C Bonds and Applications of Aziridine ...... 26 Structures and Applications of Late Metal Imido Complexes ...... 30 References ...... 43 Chapter 2: Synthesis and Characterization of Transition Metal Scorpionate Complexes 50 Introduction ...... 50 Experimental Details ...... 51 Results and Discussion ...... 61

Characterization of [(L)M(NCMe) 3](BF 4)n ...... 63 A. X-ray Crystallography ...... 63 B. Electronic Spectroscopy ...... 74 C. 1H NMR Spectroscopy ...... 85 D. FT-IR Spectroscopy ...... 93 E. Magnetic Properties ...... 101 References ...... 103 Chapter 3: Nitrene Transfer Catalysis Mediated by Transition Metal Scorpionate Complexes...... 108 Aziridination Reactions of Olefins ...... 110 Aziridination of para -Substituented Styrenes ...... 118 C-H bond Amination of Tetrahydrofuran ...... 121 C-H bond Amination of Aromatic Substrates ...... 127 8

References ...... 131

Chapter 4: Masked Lewis Acid [Fe(NCMe) 6](BF 4)2 Catalyzed Cycloaddition Reactions ...... 134 [2+1+2] Cycloaddition of Alkenes with PhI=NTs ...... 139 [3+2] Cycloadditon of Aziridine with Alkenes, Aldehydes, Ketones and Alkynes ... 144 Experimental Procedures for Chapter 3 and Chapter 4 ...... 151 References ...... 154 Chapter 5: Oxene and Nitrene Chemistry of Ni(0) Mediated by Tris(3,5-dimethylpyrazol- 1-yl)methane ...... 156 Experimental ...... 157 Results and Discussion ...... 163 References ...... 179 Appendix 1: NMR Spectrum of 2 ...... 184 Appendix 2: NMR Spectrum of 52 ...... 185 Appendix 3: NMR Spectrum of 53 ...... 186 Appendix 4: NMR Spectrum of 17 ...... 187 Appendix 5: NMR Spectrum of 15 ...... 188 Appendix 6: NMR Spectra of 16 ...... 189 Appendix 7: NMR Spectrum of 12 ...... 192 Appendix 8: NMR Spectrum of 13 ...... 193 Appendix 9: NMR Spectrum of 14 ...... 194 Appendix 10: NMR Spectrum of 32 ...... 195 Appendix 11: NMR Spectra of 45 ...... 196 Appendix 12: NMR Spectrum of 39 and 40 ...... 198 Appendix 13: NMR Spectrum of 43 and 44 ...... 200 Appendix 14: NMR Spectrum of 41 and 42 ...... 202 Appendix 15: NMR Spectrum of 37 and 38 ...... 204 Appendix 16: NMR Spectrum of 35 and 36 ...... 206 Appendix 17: NMR Spectrum of 34 and 35 ...... 208 Appendix 18: NMR Spectrum of 22 ...... 210 Appendix 19: NMR Spectrum of 23 ...... 211 Appendix 20: NMR Spectrum of 19 ...... 212 9

Appendix 21: NMR Spectra of 3 ...... 213 Appendix 22: NMR Spectra of 50 ...... 215 Appendix 23: NMR spectrum of 51 ...... 217 Appendix 24: NMR Spectra of 60 ...... 219 Appendix 25: NMR Spectra of 62 ...... 221 Appendix 26: NMR Spectra of 63 ...... 223 Appendix 27: NMR Spectra of 64 ...... 225 Appendix 28: NMR Spectrum of 69 ...... 227 Appendix 29: NMR Spectra of 65 and 66 ...... 229 Appendix 30: NMR Spectra of 67 ...... 231 Appendix 31: X-ray Crystallographic Data for Complex 2Mn ...... 233 Appendix 32: X-ray Crystallographic Data for Complex 2Ni ...... 238 Appendix 33: X-ray Crystallographic Data for Complex 3Fe ...... 243 Appendix 34: X-ray Crystallographic Data for Complex 3Co ...... 247 Appendix 35: X-ray Crystallographic Data for Complex 4Fe ...... 251 Appendix 36: X-ray Crystallographic Data for Complex 5Ni ...... 256 Appendix 37: X-ray Crystallographic Data for Complex 6Ni ...... 262 Appendix 38: X-ray Crystallographic Data for Complex 7Ni ...... 268

LIST OF TABLES

Page

Table 2.1: Selected bond distances (Å) and angles (deg) of 2Mn ...... 66

Table 2.2: Selected bond distances (Å) and angles (deg) of 2Ni ...... 67

Table 2.3: Selected bond distances (Å) and angles (deg) of 3Fe ...... 68

Table 2.4: Selected bond distances (Å) and angles (deg) of 3Co ...... 69

Table 2.5: Selected bond distances (Å) and angles (deg) of 4Fe ...... 70

Table 2.6: Selected average bond distances (Å) and angles (deg) for tris-acetonitrile complexes ...... 71

2+ Table 2.7: Average M-N bond distances (Å) of metal salts [M(NCCH 3)6] ...... 71

Table 2.8: Fe-N≡C angles (deg) of complexes 3Fe and 4Fe ...... 73

Table 2.9: UV-Vis spectra data for Fe(II) complexes 1Fe -4Fe ...... 77

Table 2.10: UV-Vis spectra data for Co(II) complexes 1Co -4Co ...... 82

Table 2.11: UV-Vis spectra data for Ni(II) complexes 1Ni -4Ni ...... 84

Table 2.12: Chemical shifts for Tpm Me,Me and Tp Me,Me -supported complexes 1M and 3M (M = Fe, Co, Ni) ...... 87

Table 2.13: Chemical shifts for Tpm Ph and Tp Ph,Me -supported complexes 2M and 4M

(M = Fe, Co, Ni) ...... 87

M M Table 2.14: FT-IR νCN absorption bands of [(L)M(NCMe)3](BF 4)2 (1 -2 ) ...... 95

M M Table 2.15: FT-IR νCN and νB-H absorption bands of [(L)M(NCMe)3]BF 4 (3 -4 ) ...... 95

M M Table 2.16: Effective magnetic moments (µ eff ) of complexes 1 -4 in CD 3CN at 295 K by Evans NMR method ...... 102

II Table 2.17: UV-Vis, Magnetic Moments and FT-IR data for [M (NCMe) n](BF 4)2 ....103 11

M M Table 3.1: Complexes 1 -4 and [Fe(CH 3CN) 6](BF 4)2 catalyzed aziridination reactions of styrene with PhI=NTs ...... 111

Table 3.2: 1Fe catalyzed aziridinations of styrene with PhI=NTs ...... 114

Table 3.3: Olefin aziridinations mediated by 1Fe with PhI=NTs ...... 117

Table 3.4: Experimental kY/kH and log(kY/kH) values ...... 119

Table 3.5: Complexes 1M-4M catalyzed amination of THF with PhI=NTs ...... 123

Me,Me Fe Table 3.6: [Tpm Fe(CH 3CN) 3] (BF 4)2 (1 ) catalyzed amination of cyclic alkane substrates with PhI=NTs ...... 126

Table 3.7: Intermolecular C-H bond amination of aromatic substrates mediated by 1Fe with PhI=NTs ...... 130

Table 4.1: [2+1+2] cycloaddition of olefins with PhI=NTs in the presence of unmasked

Lewis acid [Fe(NCMe) 6](BF 4)2 in CH 2Cl 2 ...... 142

Table 4.2: [3+2] cycloaddition of 2-phenyl-N-tosylaziridine with various dipolarophiles in the presence of unmasked Lewis acid [Fe(NCMe) 6](BF 4)2 in CH 2Cl 2 ...... 149

LIST OF FIGURES

Page

Figure 1.1: Jacobsen’s proposed redox mechanism of copper catalyzed aziridination ..29

Figure 1.2: Molecular orbital diagram of a tetragonal metal-imido complex depicting the π bonding interaction ...... 31

Figure 1.3: Isolated and structurally characterized iron-imido complexes ...... 34

Ar t Figure 1.4: Reactions of [( L)Fe(N( p- BuC 6H4)Cl] with toluene and styrene ...... 39

Ad Figure 1.5: Proposed catalytic cycle of the amination of toluene by [( L)FeCl(OEt 2)]39

Figure 2.1: Thermal ellipsoid plot of the cationic part of 2Mn ...... 66

Figure 2.2: Thermal ellipsoid plot of the cationic part of 2Ni ...... 67

Figure 2.3: Thermal ellipsoid plot of the cationic part of 3Fe ...... 68

Figure 2.4: Thermal ellipsoid plot of the cationic part of 3Co ...... 69

Figure 2.5: Thermal ellipsoid plot of the cationic part of 4Fe ...... 70

Figure 2.6: Effects of scorpionate ligands on metal to nitrogen bond lengths ...... 72

Figure 2.7: Space-filling overlay plot of 3Fe and 4Fe ...... 73

Figure 2.8: UV-Vis spectra of Mn(II) complexes 1Mn , 2Mn and 4Mn ...... 76

Figure 2.9: UV-Vis spectra of Fe(II) complexes 1Fe , 2Fe , 3Fe and 4Fe ...... 77

Figure 2.10: UV-Vis spectra of 3Fe showing the onset of spin crossover behavior ...... 78

Figure 2.11: UV-Vis spectra of Co(II) complexes 1Co , 2Co , 3Co and 4Co ...... 81

Figure 2.12: UV-Vis spectrum of 3Co ...... 81

Figure 2.13: UV-Vis spectra of Ni(II) complexes 1Ni , 2Ni , 3Ni and 4Ni ...... 83

Figure 2.14: UV-Vis spectrum of 3Ni showing the absorption band assignments ...... 83

Figure 2.15: 1H NMR spectra of Tpm Me,Me -supported complexes 1Fe , 1Co and 1Ni ...... 88 13

Figure 2.16: 1H NMR spectra of Tp Me,Me -supported complexes 3Fe , 3Co and 3Ni ...... 89

Figure 2.17: 1H NMR spectra of Tpm Ph -supported complexes 2Fe , 2Co and 2Ni ...... 90

Figure 2.18: 1H NMR spectra of Tp Ph,Me -supported complexes 4Fe , 4Co and 4Ni ...... 91

Figure 2.19: Graphical representation of complex 1Co in a dipolar double cone ...... 92

Me,Me M Figure 2.20: FT-IR spectra of [Tpm M(NCMe)3](BF 4)2 (1 ) ...... 96

Ph M Figure 2.21: FT-IR spectra of [Tpm M(NCMe)3](BF 4)2 (2 ) ...... 97

Me,Me M Figure 2.22: FT-IR spectra of [Tp M(NCMe)3]BF 4 (3 ) ...... 98

Ph,Me M Figure 2.23: FT-IR spectra of [Tp M(NCMe)3]BF 4 (4 ) ...... 99

Ni Ni Figure 2.24: FT-IR spectra of 2 and 4 , emphasizing the effect of ligand on the νCN absorption bands ...... 100

Figure 3.1: 1H NMR spectra of aziridination of styrene with PhI=NTs ...... 113

Figure 3.2: Hammett plot of experimentally determined log(kY/kH) value vs . Hammett para -substituent constant σp ...... 119

Figure 3.3: 1H NMR spectrum: Competition reaction of styrene and p-nitrostyrene mediated by 1Fe with PhI=NTs ...... 120

Figure 3.4: 1H NMR spectrum: C-H bond amination products of competition reaction

Fe of THF and THF-d8 catalyzed by 1 with PhI=NTs ...... 125

Figure 5.1: Thermal ellipsoid plot of 5Ni ...... 173

1 Me,Me 0 Me,Me Figure 5.2: H NMR spectra: A, 1:1 Tpm and [Ni (COD) 2]; B, free Tpm ; C, free COD ...... 174

Figure 5.3: Thermal ellipsoid plot of 6Ni ...... 175

1 Ni Ni Ni Figure 5.4: H NMR spectra: A, solvated 5 in wet CD 3CN; B, 6 in CD 3CN; C, 6 in Ni Ni CD 2Cl 2; D, 7 in CD 3CN; E, crude products including 8 from reaction of 1:1:1 0 Me,Me t [Ni (COD) 2]:Tpm :2- BuSO 2C6H4IO in THF, extracted into CDCl 3 ...... 176 14

Ni Ni Ni Figure 5.5: UV-Vis-NIR spectra of solvated 5 in CH 3OH, 6 in CH 2Cl 2 and 7 in

CH 3CN ...... 177

Figure 5.6: Thermal ellipsoid plot of 7Ni ...... 178

LIST OF SCHEMES

Page

Scheme 1.1: Transition metal catalyzed reactions of nitrene ...... 19

Scheme 1.2: Proposed mechanism for transition metal mediated aziridination of olefins, amination of sp 3 C-H bonds and aromatic C-H bonds ...... 19

Scheme 1.3: Schematic representation of the rebound mechanism of cytochrome P450

...... 21

Scheme 1.4: Copper(0) catalyzed reaction of benzenesulfonyl azide and cyclohexene .21

Scheme 1.5: Metal catalyzed intermolecular amination of cyclohexane ...... 23

Scheme 1.6: Metal catalyzed intramolecular amination ...... 23

Scheme 1.7: Proposed mechanism for nitrene insertion into C–H bond of cyclohexane mediated by a Mn catalyst ...... 23

Scheme 1.8: Tp Br 3Cu(NCMe) catalyzed aromatic and benzylic C-H bond aminations ..25

Scheme 1.9: AuCl 3 catalyzed aromatic and benzylic C-H bond aminations ...... 25

Scheme 1.10: Aziridination of cyclooctene with [(TMP)Mn ≡N] ...... 29

Scheme 1.11: Phenylaziridine as a masked 1,3-dipole in reaction with alkene ...... 29

Scheme 1.12: Reactions of isolated iron-imido species...... 34

Scheme 1.13: Intramolecular and intermolecular Hydrogen Atom Transfer (HAT) reactivity of an isolable iron(III)-imido complex [( Me L)Fe(NAd)( tBupy)] ...... 37

Scheme 1.14: HAT reaction of a putative iron(IV)-imido species ...... 37

2+ Scheme 1.15: Aromatic C-H bond functionalizations by [(6-PhTPA)Fe(NCMe) 2] ....37

Ar t Scheme 1.16: Synthesis of iron(III)-imido complex [( L)Fe(N( p- BuC 6H4)Cl] ...... 39

Scheme 1.17: Reaction of [(PhBP 3)Co ≡N-p-tolyl] with CO, and intramolecular C-H bond insertion of [(Tp tBu,Me )Co=NAd] ...... 41 16

Scheme 1.18: Reactivity of terminal Ni-imido complex [(Me 3NN)Ni=NAd] ...... 42

Scheme 1.19: Nitrene, phosphinidene and carbene transfer reactivities of diphosphine ligand supported Ni(II) complexes ...... 42

Scheme 2.1: Synthesis of complexes 1M-4M (M = Mn, Fe, Co, Ni) ...... 62

Scheme 3.1: Azirdination of styrene using TsNH 2 and PhI(OAc) 2 as nitrene source Me,Me Fe catalyzed by [Tpm Fe(CH 3CN) 3](BF 4)2 (1 ) ...... 115

Scheme 3.2: Competition reaction of styrene and para -substituted styrene mediated by 1Fe with PhI=NTs ...... 119

Scheme 4.1: [2+1+2] cycloaddition reaction of styrene with PhI=NTs in CH 2Cl 2 catalyzed by [Fe(NCMe) 6](BF 4)2 ...... 138

Scheme 4.2: [2+1+2] cycloaddition reaction of para -substituted styrene in CH 2Cl 2

mediated by unmasked Lewis acid [Fe(NCMe) 6](BF 4)2 with PhI=NTs ...... 143

Scheme 4.3: Formal [3+2] cycloaddition of aziridine 2 with various dipolarophiles mediated by [Fe(NCMe) 6](BF 4)2 ...... 145

Scheme 4.4: Hydrolysis of 1,3-oxazolidine derivative 64 to 1,2-amino alcohol 69 .....145

Scheme 4.5: Proposed mechanism showing the formation of 2-pyrroline derivatives by the cycloaddition of aziridine 2 and phenylacetylene 57 with [Fe(NCMe) 6](BF 4)2 .....150

CHAPTER 1: INTRODUCTION

General Aspects

C-C, C=C and C-H bonds are ubiquitous in organic molecules, pharmaceuticals and biological compounds. 1 Thus, the range of substrates for bond functionalization is virtually unlimited. Development of transition metal catalyzed bond formation reactions is fundamentally important, and the nitrene transfer reaction has great synthetic promise. 2-9 This process generally involves the generation of a metal-imido intermediate

in the presence of a nitrene precursor and a transition metal catalyst [L nM]. This metal-

imido intermediate then undergoes reaction with an organic substrate (Scheme 1.1), 3,10,11 typically more selectively than the free nitrene. Two major modes of reactivity have been observed for metal-imido intermediates. Addition of the nitrene fragment to a C=C bond in an unsaturated organic substrate such as olefin gives rise to an aziridine product. This process produces a valuable strained three-membered ring containing one nitrogen atom, which is an important moiety found in many bioactive natural products, and also serves as a significant synthetic intermediate in organic synthesis and in pharmaceuticals, owing to facile ring opening of the strained ring. 12-14 The aziridination reaction is usually postulated to proceed via a mechanism with the formation of a radical intermediate (route

A in Scheme 1.2). 15 The other reaction mode of a metal-imido intermediate is C-H bond

amination. This reactivity, which sometimes accompanies aziridination reactions, is the

insertion of the nitrene fragment into a C-H bond of the organic substrate, generating an

amine product. 3 The amination of an sp 3 C-H bond is usually proposed to proceed via a

stepwise hydrogen atom abstraction and radical rebound mechanism, with the formation 18 of a carboradical intermediate, as illustrated in route B in Scheme 1.2.15,16 On the other

hand, the direct amination of an aromatic (sp 2) C-H bond is quite different. An

electrophilic addition mechanism is usually involved in this amination process, where the

amination product is formed by electrophilic addition of nitrene radical to a phenyl C=C

bond (route C in Scheme 1.2). Therefore, both C-H bond amination and C=C bond

azridination offer a way to introduce a nitrogen atom into an organic compound. Owing

to the ubiquitous nature of C-H bonds in most organic molecules, C-H bond amination

reactions would allow for the insertion of nitrene group into many organic compounds.

On the other hand, traditional synthetic approaches of constructing C-N bonds generally

rely on the addition or substitution of a nitrogen nucleophile to a carbon electrophile.

These reactions often require the presence of polarized double bonds such as C=O, or the

presence of reactive functional groups such as a C-X bond (X = halogen, OSO 2CF 3, OTs, etc). 1 The consequences of these reaction conditions include increasing the number of steps, formation of byproducts and poor atom economy. Hence, transition metal catalyzed

C-H amination reactions would be of great synthetic value, as this method directly constructs C-N bonds, thereby shortening multi-step synthesis.

However, despite the ubiquity of C-H bonds, they are rarely considered as synthons in the scope of organic chemistry. There are two major challenges associated with C-H functionalization reactions. First, unfunctionalized C-H bonds are nonpolar, with bond dissociation energies typically between 88 – 113 kcal/mol; such strong σ bonds suppress the reactivity of C-H bonds compared to relatively more reactive C-X bonds.4 Furthermore, the chemical similarity of C-H bonds means the ability to 19 regioselectively activate a single given C-H bond within a complex organic molecule is problematic. 1 For these reasons, the successful development of a practical and efficient

C-N bond-forming reaction through direct C-H bond functionalization would be of

fundamental importance for the synthesis of natural products, pharmaceuticals and other

relevant targets.

Scheme 1.1. Transition metal catalyzed reactions of nitrene. 3

Scheme 1.2. Proposed mechanism for transition metal mediated aziridination of olefins (route A), amination of sp 3 C-H bonds (route B) and aromatic C-H bonds (route C) 20

C-H Bond Amination Reactions

As mentioned above, functionalization of unactivated C-H bonds represents a significant challenge in synthetic chemistry. 1,17 In nature, oxidation reactions such as C-H bond functionalization generally involve enzymes as catalysts. 17 This is primarily

achieved by utilizing iron-containing enzymes such as cytochrome P450 as the catalyst

and dioxygen as the terminal oxidant. Many studies have provided insight into the

mechanism of C-H functionalization reactions catalyzed by the cytochrome P450 family.

The consensus mechanism for the oxidation reaction, suggested by Groves and co-

workers, is the rebound mechanism, shown in Scheme 1.3.18-20 A transient terminal

iron(IV)-oxo porphyrin radical species (compound I), which is formally oxidized by two

electrons relative to the ferric resting state, is the key intermediate in the C-H

functionalization process. 20-22 An alkyl radical and an iron(IV)-hydroxo intermediate

(compound II) are formed from the initial hydrogen atom abstraction from an alkane

(RH) substrate by the active iron(IV)-oxo species, then the alkyl radical combines with the iron(IV)-hydroxo intermediate to generate an iron(III)-alcohol complex, which then

20 releases the alcohol and restores the resting state, an iron(III)-OH 2 complex.

Scheme 1.3. Schematic representation of the rebound mechanism of cytochrome P450 20

Scheme 1.4. Copper(0) catalyzed reaction of benzenesulfonyl azide and cyclohexene. 23

Inspired by biological C-H bond functionalization reactions, especially heme iron catalyzed C-H bond hydroxylation reactions, C-H bond amination reactions utilizing transition metal complexes as catalysts have received a lot of attention from many workers. 4,5,16 In 1967, Kwart and Khan first proposed a copper-imido species obtained

from the decomposition of benzenesulfonyl azide in the presence of powdered copper

metal in cyclohexene. This reaction gave numerous products (Scheme 1.4), most of

which were consistent with the formation of a copper-imido species as a reactive

intermediate. 23 In 1982, Breslow and co-workers first reported the catalytic transfer of nitrene to alkanes (Scheme 1.5). 24 Intermolecular amination of cyclohexane was achieved by using ( p-toluenesulfonyl)iminophenyliodinane (PhI=NTs, Ts = p-toluenesulfonyl) as nitrene source in the presence of either [Mn(TPP)Cl] or [Fe(TPP)Cl] (TPP = 5, 10, 15,

20-tetraphenylporphyrin) as metal catalyst, although the yields of cyclohexane sulfonamides were not synthetically useful (3.1- 6.5%). Intramolecular benzylic C-H bond nitrene insertion of N-(2,5-diisopropylbenzenesulfonyl)iminophenyliodinane was reported by the same group in 1983, with a variety of catalysts (Scheme 1.6). 25 The intramolecular amination reaction turned out to be much more efficient, achieving the cyclic sulfonamide product with up to 86% yield. Then Breslow and co-workers also reported the insertion of a nitrene fragment into a C-H bond of cyclohexane, with cytochrome P450 as the catalyst. It is noteworthy that a high-valent iron-imido complex was proposed as the key intermediate. 26

Scheme 1.5. Metal catalyzed intermolecular amination of cyclohexane. 24

Scheme 1.6. Metal catalyzed intramolecular amination. 25

Scheme 1.7. Proposed mechanism for nitrene insertion into C–H bond of cyclohexane mediated by a Mn catalyst. 27 24

Following the seminal work of Breslow and co-workers, Mansuy and co-workers achieved the amination of saturated C-H bonds of cyclohexane and adamantane in the presence of PhI=NTs as a nitrene precursor and a series of iron and manganese porphyrin complexes as the catalyst, with 3.1-15% yields for amination of cyclohexane and 19-56% yields for adamantane, respectively. Notably, an H-atom abstraction and radical rebound mechanism involving a reactive high valent Mn-imido intermediate was proposed for the

[Mn(TDCPP)(CF 3SO 3)] (TDCPP = 5, 10, 15, 20-tetrakis{2,6-dichlorophenyl}porphyrin) catalyzed amination reaction (Scheme 1.7). 27,28

Besides the C-H bond amination reactions mentioned above, other impressive

reactivity using Mn, 29 Co, 30 Cu 31,32 and Ag 33 complexes have also been demonstrated to

induce similar nitrene insertion to C-H bonds. However, many of the C-H bond

amination reactions reported were achieved by insertion of a nitrene group into allylic or

benzylic C-H bonds, or through intramolecular C-H bond amination processes, 34 while

the analogous amination of aromatic C-H bonds is less well explored. 2

Pérez and co-workers recently demonstrated the catalytic nitrene insertion into C-

H bonds of cyclohexane, toluene, mesitylene and benzene using a Cu(I) complex

Br Br 35 [Tp 3Cu(NCMe)] (Tp 3 = hydrotris{3,4,5-tribromopyrazolyl}borate) as catalyst. The

Cu(I) catalyst successfully promoted the nitrene insertion into a C-H bond of benzene

with 40% yield at room temperature (eq. 1 in Scheme 1.8). However, when toluene and

mesitylene were used as the reaction substrates, the functionalization reactions

exclusively took place onto benzylic C-H bonds, with yields up to 95% (eqs. 2, 3 in

Scheme 1.8). 25

NHTs PhI=NTs (eq. 1) TpBr3Cu(NCMe) (5 mol%), rt 40% yield

Me PhI=NTs NHTs (eq. 2) TpBr3Cu(NCMe) (5 mol%), rt > 95% yield

Me Me Me PhI=NTs NHTs (eq. 3) TpBr3Cu(NCMe) (5 mol%), rt Me Me > 95% yield Scheme 1.8. [Tp Br 3Cu(NCMe)] catalyzed aromatic and benzylic C-H bond aminations. 35

AuCl (2 mol%) 3 (eq. 1) PhI=NNs NHNs

HCl AuCl3 AuCl3 (2 mol%) PhI=NNs

HCl AuCl NHNs AuCl2 2

for weaker PhI=NNs benzylic C-H

NHNs

PhI=NNs HCl

AuCl2

36 Scheme 1.9. AuCl 3 catalyzed aromatic and benzylic C-H bond aminations.

The direct insertions of the nitrene fragment (NNs, Ns = p-nitrobenzenesulfonyl)

into the C-H bonds of several alkyl substituted aromatic substrates were carried out by He

36 and co-workers with AuCl 3 as the catalyst. This was the first example introducing a gold complex as a catalyst to induce the transformation of C-H bonds into C-N bonds.

Surprisingly, amination of methyl-substituted aromatics such as 1,3,5-trimethylbenzene gave solely the aromatic C-H bond insertion products (eq. 1 in Scheme 1.9), without any observation of benzylic C-H bond functionalization products. Only when isopropyl groups with weaker benzylic C-H bonds were present, these were functionalized as well as aromatic C-H bonds. With isotope labeling studies, they proposed that the unique chemoselectivity toward aromatic C-H bond functionalization was due to the formation of arylgold(III) species. This unique mechanism is different from those mentioned above, where high valent metal-imido species were proposed to be key intermediates. In this catalytic cycle, the aromatic C-H bond is activated by the gold center, to form an arylgold(III) intermediate, along with elimination of HCl. The nitrene precursor

(PhI=NNs) is then activated through the interaction with the arylgold(III) intermediate.

Finally, HCl reacts with the adduct, giving amine product and regenerating the AuCl 3 catalyst (Scheme 1.9).

Aziridination of C=C Bonds and Applications of Aziridine

Since Gabriel first discovered the smallest nitrogen-containing heterocyle in 1888, aziridines have gained considerable attention as synthetic targets as well as useful synthetic building blocks in organic synthesis and pharmaceutical chemistry. 37 Attracted by the unique reactivity and high chemical and biological activity of the three-membered 27 ring, synthetic chemists have extensively explored the various strategies for aziridine ring formation. 12,14 Although myriad achievements have been made on transition metal

catalyzed oxygen atom transfer reactions to C=C bonds to form epoxides, 38,39 the analogous nitrene transfer reactions to form aziridines have been less well developed. All this was changed with the significant discovery of PhI=NTs ({ p-toluenesulfonyl}- iminophenyliodinane) and its analogues by Yamada and co-workers in 1975. 40 Since intense efforts have been contributed to the advancement of transition metal mediated aziridination reactions. 2

In 1984, Mansuy and co-workers reported the first example of an iron complex catalyzed azirdination reaction, using [Fe(TTP)Cl] (TTP = 5,10,15,20-tetrakis{4- methylphenyl}porphyrin). 10 A significant advance in this area was the seminal work achieved by Evans and co-workers in 1994: nitrene transfer to a wide variety of olefins was obtained using Cu(I) or Cu(II) salts as catalyst and PhI=NTs as nitrene precursor. 41

Moreover, Evans and co-workers achieved the asymmetric aziridination of trans - cinnamate esters catalyzed by CuOTf with the chiral ligand PhBOX ({S,S}-2,2’- isopropylidene-bis{4-phenyl-2-oxozoline}) as a supporting ligand and PhI=NTs as nitrene precursor. 42 Jacobsen and co-workers also achieved the asymmetric aziridination of various alkenes with chiral diimine ligand supported Cu(I) catalysts. Notably, mechanistic studies suggested that the (diimine)copper(I) catalyzed aziridination reactions proceed through a high-valent Cu(III)-imido intermediate (Figure 1.1). 43,44

Recently, Abu-Omar and co-workers reported nitrene transfer from ArI=NTs (Ar = 2-

{tert -butylsulfonyl}benzene, Ts = p-toluenesulfonyl) to styrene substrates catalyzed by a 28

Mn(III) corrole complex [(TPFC)Mn] (TPFC = 5,10,15-tris{pentafluorophenyl}corrole).

Significantly, they revealed that the high-valent Mn(V)-imido species [(TPFC)Mn=NTs] is not the nitrene transfer reagent; double-labeling experiments suggested that the oxidant in this aziridination reaction is an iminoiodinane (ArI=NTs) adduct of a pre-formed imido

Mn(V) species, [(TPFC)Mn(NTs tBu )(ArINTs)]. 45

Groves and co-workers reported a Mn(V)-nitrido porphyrin complex

[(TMP)Mn ≡N] (TMP = 5,10,15,20-tetramesityl-porphyrin), which forms a Mn(V)-

acylimido trifluoroacetate complex when reacted with trifluoroacetic anhydride. Notably,

this Mn(V)-acylimido species exhibited stoichiometric transfer of the nitrene moiety

CF 3CON to cis -cyclooctene to furnish the N-trifluoroacetyl-protected aziridine (Scheme

1.10). 46 Various other transition metals have also been employed in olefin aziridination

reactions including Fe, 47-51 Co, 52 Ag, 6,53 Au, 54 Ru 15 and Re 55 .

Aziridines exhibit a wide range of useful reactivities including regioselective

nucleophilic ring opening, which harnesses the release of ring strain. 13,14 Recently, transformations of aziridines to five-membered nitrogen-containing heterocycles through formal [3+2] cycloaddition reactions have been described. 56 Cycloaddition reactions of aziridines with CO 2 and CS 2 forming 1,3-oxazolidine-2-ones and urethanes, respectively, have been reported by Endo and co-workers. 57 Alkenes, 58-60 alkynes, 61,62 carbonyls and nitriles 63-65 have also been employed as dipolarophiles leading to the formation of valuable five-membered nitrogen-containing heterocycles.

Figure 1.1. Jacobsen’s proposed redox mechanism for copper catalyzed aziridination (Adapted with permission from ref. 43, Copyright [1995] American Chemical Society)

Scheme 1.10. Aziridination of cyclooctene with [(TMP)Mn ≡N] (Adapted with permission from ref. 46, Copyright [1983] American Chemical Society).

Scheme 1.11. Phenylaziridine as a masked 1,3-dipole in reaction with alkene (Adapted with permission from ref. 59, copyright [2000] John Wiley and Sons).

Mann and co-workers first reported the formation of a unique 1,3-dipole generated from 2-phenyl-N-tosylaziridine through C-N bond breaking in the presence of

Lewis acid. 59 The conversion of 2-phenyl-N-tosylaziridine into substituted pyrrolidines

have been achieved through the formal [3+2] cycloaddition reactions of 2-phenyl-N-

tosylaziridine with inactivated alkene substrates, in the presence of a stoichiometric

amount of BF 3·Et 2O (Scheme 1.11). Singh and co-workers have demonstrated analogous

[3+2] cycloaddition reactions of aryl substituted N-tosylaziridines with carbonyls

(aldehydes or ketones) and nitriles as dipolarophiles, in the presence of a stoichiometric

63 amount of BF 3·Et 2O or a catalytic amount of Zn(OTf) 2. The [3+2] cycloaddition reactions proceeded smoothly in CH 2Cl 2, converting carbonyls or nitriles into

oxazolidines or imidazolines with moderate to good yields. Nguyen and co-workers also

achieved the analogous conversion of carbonyls into 5-alkyl-1,3-oxazolidines through

cycloaddition reactions of carbonyls with less reactive 2-alkyl substituted-N-

66 tosylaziridines in the presence of 20 mol% of Sc(OTf) 3. Cycloadditions of alkynes with aziridines affording 2-pyrroline derivatives were also reported by Wender 62 and Wang

61 groups with AgSbF 6 and FeCl 3 as catalysts, respectively. For a general review of π- nucleophiles, see Krake and Bergmeier. 12

Structures and Applications of Late Metal Imido Complexes

Terminal imido complexes of the late first row transition metals are usually

implicated as intermediates in transition metal catalyzed nitrene transfer reactions. 67,68

However, little was known about the structure of the presumed metal-imido

This is typically ascribed to the lack of empty d orbitals of late transition metals available 31 to accept π donation from an imido moiety (NR). 68,69 The bonding of the imido ligand with metal d orbitals can be explained by molecular orbital theory in a tetragonal geometry as depicted in Figure 1.2. 68 Considering the principal axis (z) to lie along the

M-N bond, the π bonds of metal-imido species are formed by the interaction of the metal dxz , d yz orbitals and the N atom p x, p y orbitals. Therefore, for productive π bonding to occur, the metal must have empty d orbitals of π symmetry to accept donation from the

imido moiety, This is true for early and middle transition metals, since most of the d

orbitals of these metals are empty; therefore, it is not surprising that high-valent early

transition metal-imido species are stable and well explored. 68,69

Figure 1.2. Molecular orbital diagram of a tetragonal metal imido complex depicting the π bonding interaction (Adapted with permission from ref. 68, copyright [2003] Elsevier)

Although iron-imido species were implicated as nitrene transfer intermediates, 25 it

was not until the year 2000 that Lee and co-workers isolated the first stable and

structurally characterized terminal iron(IV)-imido complex. 70 The reaction of ferric chloride and lithium t-butylamide gave rise to a tetranuclear iron cluster in very low yield. This tetranuclear iron cluster contains three iron(III) and one iron(IV) centers.

These four iron centers are bridged by four t-butylimide ligands and the iron(IV) center has a terminally bonded t-butylimide ligand (Figure 1.3).

Since then, several stable, structurally characterized examples of terminal iron- imido complexes have been reported (Figure 1.3). 71 Similar to the synthesis of mononuclear cobalt-imido species, 72 Peters and co-workers reported the first example of a mononuclear iron(III)-imido complex, featuring a tetrahedral iron center supported by bulky tris(phosphino)borate ligand. 73 This iron(III)-imido complex was prepared via two- electron oxidative nitrene group transfer from an aryl azide, using a low-valent iron(I) complex. Subsequently, the Peters group and the Smith group reported mononuclear iron(IV)-imido complexes, featuring tetrahedral iron centers supported by bis(phosphine)-pyrazolylborate 74 and tris(carbene)borate ligands,75 respectively. These

two iron complexes were prepared in a fashion similar to Peters’ iron(III)-imido complex.

The iron(I) precursors were treated with aryl azides to give the corresponding iron(III)-

imido complexes, which were further oxidized to give iron(IV)-imido complexes. A

highly distorted square planar terminal iron(III)-imido complex [( iPr PDI)Fe=NAr] ( iPr PDI

i 76 = {2,6- Pr 2C6H3N=CMe} 2C5H3N) was reported by Chirik and co-workers. And then

Power and co-workers reported a bis(imido)iron(V) complex with trigonal planar 33 geometry via the reaction of a sterically encumbered iron(I) precursor and aryl azide

77 N3(1-Ad).

The iron(III)-imido complexes have been demonstrated to be able to undergo nitrene transfer reactions and hydrogenation reactions, but no aziridination or C-H bond amination reactivity. Treatment of the iron(III)-imido complex [(PhBP 3)Fe ≡N-p-tolyl]

with carbon monoxide (CO) at room temperature immediately and quantitatively gave p- tolyl isocyanate O=C=N-p-tolyl and iron(I) byproduct [(PhBP 3)Fe(CO) 2] (eq. 1 in

73 Scheme 1.12). [(PhBP 3)Fe ≡N-p-tolyl] also represents the first example of a metal-imido complex that can undergo hydrogenation reactions. 78 It was found that the exposure of

[PhBP 3]Fe ≡N-p-tolyl to one atmosphere of hydrogen gas in benzene for three hours gave an iron(II)-amido complex [PhBP 3]Fe(NH-p-tolyl) as the major product at room temperature. Prolonged hydrogenation of [PhBP 3]Fe ≡N-p-tolyl in benzene for three days

led to the formation of a new diamagnetic compound through the partial hydrogenation of

the benzene solvent (eq. 2 in Scheme 1.12). The iron(III)-imido complex ( iPr PDI)Fe=NAr

was also found to react with hydrogen gas to give an iron-dihydrogen species

iPr 76 ( PDI)Fe(H 2), with aniline as organic product (eq. 3 in Scheme 1.12).

tBu 0 or + N Ar Ad N N t Fe Bu t tBu Bu Fe Fe t tBu Bu N N N Ph Ph R tBu P P PPh N P t Ph2P 2 Bu Fe Fe Fe N Cl Cl B Cl B N R Ph Ph tBu Ar = p-tolyl R = H, Me Lee's iron-imido cubane Peters' iron(III)-imido Peters' iron(III)- and iron(IV)-imido

0 or + Ad Ad Ad N N N Ar Ar Fe Ar N Fe N N N Ar N Fe N Ar Ar Ar N N N N B Ar iPr iPr Ph

Ar = Mes Ar = 2, 6-iPr2C6H3 Ar = 2, 4, 6-iPr2C6H3

Chirik's iron(III)-imido Smith's iron(III)- and iron(IV)-imido Power's bis(imido)iron(V) (iPrPDI)Fe=NAr

Figure 1.3. Isolated and structurally characterized iron-imido complexes. 70,71,73-77

Ar N OC CO Fe Fe Ph Ph CO(g) Ph Ph P PPh P PPh Ph2P 2 Ph2P 2 ArNCO (eq. 1) p-TsN3 B B Ar = p-tolyl Ph Ph H Ar Ar H N NH Fe Fe Fe Ph Ph Ph Ph Ph Ph P 1 atm. H P 1 atm. H Ph P PPh2 2 PPh 2 P PPh 2 Ph2P 2 Ph2P 2 ArNH2 rt, 3h rt, 3d benzene benzene B B B (eq. 2) Ph Ar = p-tolyl Ph Ph

NH2

N 1 atm. H2 N Ar N Fe N Ar Ar N Fe N Ar (eq. 3) Rn NAr HH Scheme 1.12. Reactions of isolated iron-imido species (Adapted with permission from ref. 71, copyright [2011] Springer).71,73,76,78 35

The hydrogen atom transfer (HAT) reactivity of iron-imido complexes has been less well investigated than their oxo counterparts.79 Recently, Holland and co-workers reported the first isolated iron(III)-imido complex that was able to accomplish both intramolecular and intermolecular HAT reactions, suggested by large substrate kinetic isotope effects. 80 The terminal iron(III)-imido species [( Me L)Fe(NAd)( tBupy)] ( Me L = β-

diketiminate ligand, 2,4-bis{2,6-diisopropylphenylimido}pentyl) was decomposed to

form an iron(III)-amido species [( Me* L)Fe(NHAd)( tBupy)] within a few hours at room

temperature. The ligand was proposed to undergo intramolecular C-C bond coupling via

HAT reaction (eq. 1 in Scheme 1.13). Treatment of [( Me L)Fe(NAd)( tBupy)] with 1,4- cyclohexadiene rapidly afforded an iron(II)-amido species [( Me L)Fe(NHAd)( tBupy)] and benzene at -51 oC (eq. 2 in Scheme 1.13). The intermolecular HAT reaction of

[( Me L)Fe(NAd)( tBupy)] was limited to those substrates that contain weak C-H bonds.

When hydrocarbons with stronger C-H bonds such as toluene (benzylic C-H BDE ~89 kcal/mol) were present, intramolecular HAT reactivity was observed instead of an intermolecular reaction.

Borovik and co-workers isolated an iron(III)-amido species, formed from the reaction of an iron(II) complex with p-tolyl azide ( p-tolN 3) in dimethylacetamide (DMA).

This iron(III)-amido species was proposed to form from the intermolecular hydrogen

atom abstraction of DMA solvent with the putative iron(IV)-imido intermediate (Scheme

1.14). 81 Although iron-imido complexes mentioned above displayed reactivities toward

hydrogen atom transfer and/or nitrene group transfer, the studies of iron-imido

intermediates involved in iron catalyzed C-N bond formation reactions are rare. Que and 36 co-workers reported an aromatic amination reaction on the ligand when they treated tridentate iron(II) complex [(6-PhTPA)Fe(NCMe) 2](ClO 4)2 (TPA = tris{2- pyridylmethyl}amine) with solid PhI=NTs. 82 The amination reaction was proposed to

proceed via a high valent iron(IV)-imido intermediate, which then gave an iron(III)-

amido complex after hydrogen atom abstraction (Scheme 1.15).

Scheme 1.13. Intramolecular (eq.1) and intermolecular (eq. 2) Hydrogen Atom Transfer (HAT) reactivity of an isolable iron(III)-imido complex [( Me L)Fe(NAd)( tBupy)] (Adapted with permission from ref. 80, Copyright [2011] American Chemical Society).

Scheme 1.14. Hydrogen atom abstraction reaction of a putative iron(IV)-imido species. 81

2+ 82 Scheme 1.15. Aromatic C-H bond functionalizations by [(6-PhTPA)Fe(NCMe) 2] .

Only recently was the isolation and structural characterization of a reactive iron(III)-imido complex, which was proved to be the key intermediate in catalyzed amination and aziridination reactions, described by Betley and co-workers. 16 They found

Ar Ar that treatment of [( L)FeCl] ( L, 1,9-Ar 2-5-mesityl-dipyrromethene, Ar = 2,4,6-

t Ph 3C6H2) with aryl azide p- BuC 6H4N3 afforded a terminal iron(III)-imido complex

Ar t [( L)Fe(N(p- BuC 6H4)Cl] (Scheme 1.16). Theoretical analyses of the iron(III)-imido

Ar t species [( L)Fe(N( p- BuC 6H4)Cl] suggested that this species contains a high spin

5 iron(III) ( S = /2) center, which is antiferromagnetically coupled to an imido-based

1 Ar radical ( S = /2). Therefore the total spin of this iron species is S = 2. [( L)Fe(N( p- t BuC 6H4)Cl] was found to be able to effectively insert the nitrene fragment into the C-H

bond of toluene as well as transfer the nitrene moiety to C=C bond of styrene (Figure

Ar t 1.4). The unique reactivity of [( L)Fe(N( p- BuC 6H4)Cl], which is distinct from other isolated iron-imido complexes, is presumably due to the high spin nature of the complex and the radical character of the nitrene moiety. Catalytic amination of toluene and

Ad aziridination of styrene were also achieved using the iron(II) precursor [( L)FeCl(OEt 2)]

and adamantyl azide. The kinetic isotope effect study of C-H bond amination of toluene

provided kH/kD = 12.8(5). This KIE value suggested an H atom abstraction mechanism for

Ad the C-H bond amination of toluene catalyzed by [( L)FeCl(OEt 2)] (Figure 1.5).

Ar t Scheme 1.16. Synthesis of terminal iron(III)-imido complex [( L)Fe(N( p- BuC 6H4)Cl] (Adapted with permission from ref. 16, Copyright [2011] American Chemical Society)

Ar t Figure 1.4. Reactions of [( L)Fe(N( p- BuC 6H4)Cl] with toluene and styrene (Adapted with permission from ref. 16, Copyright [2011] American Chemical Society).

Ad Figure 1.5. Proposed catalytic cycle for the amination of toluene by [( L)FeCl(OEt 2)] (Adapted with permission from ref. 16, Copyright [2011] American Chemical Society) 40

Besides iron-imido species, other imido complexes of metals such as cobalt and nickel have also been isolated. Peters and co-workers isolated a terminal Co(III)-imido complex, [(PhBP 3)Co ≡N-p-tolyl] supported by bulky tris(phosphino)borate ligand

PhBP 3, by using the same synthetic strategy as for preparing the iron(III)-imido

complex. 72 Notably, this Co(III)-imido species also transfers its imide group from cobalt to CO gas, releasing the free isocyanate O=C=N-p-tolyl (eq. 1 in Scheme 1.17). Theopold and co-workers were also able to isolate a stable terminal Co(III)-imido species

tBu,Me tBu,Me [(Tp )Co=NAd], by treating a THF solution of [(Tp )Co(N 2)] with one

tBu,Me equivalent of adamantyl azide (AdN 3) at room temperature. [(Tp )Co=NAd] was also found to deliver the imide moiety to CO, forming free isocyanate O=C=NAd.

Interestingly, they found that heating a solution of [(Tp tBu,Me )Co=NAd] at 40ºC in the

presence of ethylene, the intramolecular insertion of the imide moiety NAd of

[(Tp tBu,Me )Co=NAd] into a C-H bond of one of the tert -butyl groups of the Tp ligand was

observed, while the olefin was not functionalized (eq. 2 in Scheme 1.17). 83 Warren and co-workers reported the isolation of diketiminate ligand supported terminal Co(III)-imido complex [(Me 2NN)Co ≡NAd] (Ad = 1-adamantyl). However, in contrast to Peters and

Theopold’s terminal Co(III)-imido species, Warren’s imido complex exhibited no nitrene transfer reactivity. 84

Warren and co-workers demonstrated stoichiometric hydrogen atom transfer with a isolated diketiminate supported terminal Ni(III)-imido complex, [(Me 3NN)Ni=NAd].

[(Me 3NN)Ni=NAd] rapidly reacts with 1,4-cyclohexadiene, giving a Ni(II)-amide complex, [(Me 3NN)Ni-NHAd]. [(Me 3NN)Ni=NAd] was also found to be able to deliver 41

t an imido group to various substrates such as CO, CNBu , and PMe 3, affording

t 85 AdN=C=NBu and Me 3P=NAd, respectively, in good yields (Scheme 1.18). Hillhouse and co-workers reported the crystal structure of bulky diphosphine ligand supported diamagnetic Ni(II)-imido complex [(dtbpe)Ni=NAr] (dtbpe = 1,2-bis{di-tert - butylphosphino}ethane; Ar = 2,6-di-isopropylphenyl). It is worth noting that this diphosphine ligand was also found to stabilize isolobal phosphinidene and carbene groups, forming analogous diamagnetic Ni(II) complexes, [(dtbpe)Ni=P(dmp)] (dmp =

2,6-dimesitylphenyl) and (dtbpe)Ni=CPh 2, respectively. Significantly, they discovered that these isolated imido, phosphinidene and carbene complexes of Ni(II) could undergo group transfer to ethylene, forming the three-membered ring compounds, aziridine, phosphirane and cyclopropane, respectively (Scheme 1.19). 86

Scheme 1.17. Reaction of [(PhBP 3)Co ≡N-p-tolyl] with CO (eq.1), and intramolecular C- H bond insertion of [(Tp tBu,Me )Co=NAd] (eq.2). 72,83

Scheme 1.18. Reactivity of terminal Ni-imido complex [(Me 3NN)Ni=NAd] (Adapted with permission from ref. 85, Copyright [2005] American Chemical Society).

Scheme 1.19. Nitrene, phosphinidene and carbene transfer reactivities of diphosphine ligand supported Ni(II) complexes (Adapted with permission from ref. 86, Copyright [2003] American Chemical Society).

tris{3,5-dimethylpyrazol-1-yl}methane, Tpm Me,Me , M = Mn, Fe, Co, Ni, n = 2; L = tris{3-

phenylpyrazol-1-yl}methane, Tpm Ph , M = Mn, Fe, Co, Ni, n = 2; L = hydrotris{3,5-

dimethylpyrazol-1-yl}borate, Tp Me,Me , M = Fe, Co, Ni, n = 1; L = hydrotris{3-phenyl-5- methylpyrazol-1-yl}borate, Tp Ph,Me , M = Mn, Co, Fe, Ni, n = 1) were prepared and

characterized. These complexes were utilized as metal catalysts for nitrene transfer from

phenyl-N-tosyliminoiodinane (i.e., PhI=NTs) to variety of organic substrates, resulting in

olefin aziridination and C-H bond amination with varying degrees of efficiency. A wide

range of organic products was obtained and fully characterized, and reaction mechanisms

were probed with Hammett and kinetic isotope effects.

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CHAPTER 2: SYNTHESIS AND CHARACTERIZATION OF TRANSITION METAL

SCORPIONATE COMPLEXES

Introduction

The family of hydrotris(pyrazolyl)borates (Tp) have been extensively employed in bioinorganic, coordination and organometallic chemistry. 1-4 Such versatile ligands typically adopt κ2 or κ3 coordination modes toward a metal center, thus resembling the action of a scorpion and therefore are nicknamed “scorpionate” ligands. Certain transition metal complexes stabilized by Tp ligands were found to catalyze a variety of chemical reactions, including C-H bond activation reactions, carbene transfer reactions and nitrene transfer reactions. For instance, activation of aliphatic and aromatic C-H bonds has been

Me,Me 5 achieved by photolysis of Tp Rh(CO) 2, which proceeded with loss of CO. Pérez and

co-workers employed [Tp Br 3Cu(NCMe)] as a catalyst to effect C-H bond amination of

cyclohexane and benzene. 6 A variety of Tp RCu complexes were found to catalyze the

reaction of carbene precursor ethyl diazoacetate and nitrene precursor PhI=NTs with

olefins to form cyclopropanes and aziridines, respectively. 7-10 Compared with anionic

scorpionate ligands Tp, the chemistry of metal complexes supported by the neutral

analogous tris(pyrazolyl)methanes (Tpm) remains underdeveloped. Isoelectronic

TpmM 2+ and TpM + Lewis acid centers should show varying catalytic activities. The

greater positive charge on the metal center in the Tpm cases should cause TpmM 2+ to be more electrophilic than its less positively charged TpM + analogue. Therefore, the

TpmM 2+ fragment should exhibit greater catalytic reactivity toward nitrogen atom

transfer reactions. Pérez and co-workers reported the nitrene transfer ability of 51

R 11 [Tpm Cu(NCMe)]BF 4 in ionic liquid. On the other hand, despite Cu(I) complexes supported by scorpionate ligands (Tp R and Tpm R) having been successfully employed as catalysts in nitrene transfer reactions, the later first-row transition metal (Mn, Fe, Co, Ni) analogs have not been investigated. In this present work, we describe the preparation and characterization of labile MeCN-coordinated transition metal complexes,

M Me,Me [(L)M(NCMe)3](BF 4)n (1 , L = tris{3,5-dimethylpyrazol-1-yl}methane, Tpm , M =

Mn, Fe, Co, Ni, n = 2; 2M, L = tris{3-phenylpyrazol-1-yl}methane, Tpm Ph , M = Mn, Fe,

Co, Ni, n = 2; 3M, L = hydrotris{3,5-dimethylpyrazol-1-yl}borate, TpMe,Me , M = Fe, Co,

Ni, n = 1; 4M, L = hydrotris{3-phenyl-5-methylpyrazol-1-yl}borate, Tp Ph,Me , M = Mn, Co,

Fe, Ni, n = 1).12,13 Such transition metal complexes could turn out to be potentially useful catalysts toward nitrene transfer reactions, partially owing to the lability of the solvento ligand CH 3CN, which can be readily replaced by other nucleophiles.

Experimental Details

General Procedures . All manipulations were carried out under an inert atmosphere of prepuriﬁed argon, either in a glovebox (MBraun Unilab) or using Schlenk techniques. Tris(3,5-dimethylpyrazol-1-yl)methane (Tpm Me,Me ), tris(3-phenylpyrazol-1-

yl)methane (Tpm Ph ) and hydrotris(pyrazol-1-yl)borate thallium complexes TlTp R,Me (R =

Me, Ph) were prepared by local modification of literature procedures (Caution! Thallium salts are extremely toxic and must be properly handled and disposed of ).14-16 Metal salts,

[M(NCMe)n](BF 4)2 (M = Mn, n = 4; M = Fe, Co, Ni, n = 6), were prepared by literature

17 M Me,Me procedures as described below. Complexes [(L)M(NCMe)3](BF 4)n (1 , L = Tpm ,

M = Mn, Fe, Co, Ni, n = 2; 2M, L = Tpm Ph , M = Mn, Fe, Co, Ni, n = 2; 3M, L = Tp Me,Me , 52

M = Fe, Co, Ni, n = 1; 4M, L = Tp Ph,Me , M = Mn, Co, Fe, Ni, n = 1) were prepared by

Me,Me modification of literature procedures from reactions of [M(NCMe)n](BF 4)2 and Tpm ,

Ph R,Me 12 Tpm and TlTp (R = Me, Ph), respectively, in CH 3CN/CH 2Cl 2. Manganese metal

chips, iron powder, cobalt powder, and nickel powder were purchased from Aldrich and

used without further purifications. Dichloromethane (CH 2Cl 2) and acetonitrile (CH 3CN)

were degassed and distilled over calcium hydride (CaH 2) before use. Diethyl ether (Et 2O) was degassed and distilled over sodium/benzophenone (Na/Ph 2CO). Deuterated solvents chloroform-d and acetonitrile-d3 were vacuum-transferred from CaH 2 and degassed by the freeze-pump-thaw method prior to use. 1H NMR data were recorded on a Varian

Unity 500 spectrometer and processed using the MestReNova software suite (Mestrelab

Research, Santiago de Compostela, Spain); spectra were referenced internally to the residual CH 3CN solvent resonance (1.94 ppm). Solution magnetic moments of

M M [(L)M(NCMe)3](BF 4)n (1 -4 ) were determined by the Evans NMR method in CD 3CN at

295 K. 18 FT-IR spectra were recorded from KBr pellets on a Thermo-Electron Nicolet

380 spectrophotometer. UV–visible-NIR spectra were recorded on an Agilent HP-8453

diode-array spectrophotometer; heating and cooling were controlled by a VMR bath.

Elemental analyses were performed by Atlantic Microlabs, Inc. (Norcross, GA); as

previously noted, analytical data for the scorpionate complexes were not successful due

to solvento ligand loss. 12,13

17 Preparation of [M(CH 3CN) 6](BF 4)2 (M = Fe, Co, Ni). In general, 1.0 g of

NOBF 4 (8.64 mmol) and powdered metal (M= Fe, Co, Ni) (0.59 g, 0.63 g, 0.62 g, repectively, 10.64 mmol) were loaded into a 500 mL Schlenk flask in a glovebox. 53

Distilled CH 3CN (80 mL) was added, and the mixture was stirred at room temperature

and the flask was exposed to vacuum until the solution began to bubble vigorously. The

flask was then backfilled with nitrogen, and this process was repeated three additional

times to remove the liberated NO gas (Caution! NO gas is extremely toxic ). The mixture

was allowed to stir at room temperature overnight and was then filtered through a frit.

Solvent was then evaporated under vacuum until the solution became cloudy, then Et 2O

(50 mL) was added to complete the precipitation. The mixture was allowed to cool down

in a freezer (-37 ºC) to allow the solid to settle. The solid product was recovered by

filtration, washed with Et 2O (20 mL) twice, and thoroughly dried under vacuum. Yields

were 1.40 g (2.94 mmol, 68%) for the white Fe(II) product, 1.72 g (3.59 mmol, 83%) for the pink Co(II) solid, and 1.83 g (3.82 mmol, 89%) for the blue Ni(II) compound.

17 Preparation of [Mn(CH 3CN) 4](BF 4)2. Manganese metal chips (1.60 g, 29.1 mmol, excess) and NOBF 4 (1.64 g, 14.0 mmol) were added to a 500 mL Schlenk flask in a glovebox. Distilled CH 3CN (40 mL) was added with stirring and the NO(g) was allowed to escape through a needle outlet placed in a septum. After stirring overnight, the reaction mixture was filtered and the colorless filtrate was concentrated under vacuum to about 5 mL. Et 2O (40 mL) was added and the flask was cooled to -37 ºC to produce a white precipitate. Solvent was removed and the solid was washed with Et 2O (20 mL) twice and dried under vacuum to yield a white crystalline product. Yield 2.32 g (5.90 mmol, 84%).

Me,Me Mn Preparation of [Tpm Mn(NCMe) 3](BF 4)2 (1 ). To the solution of

[Mn(NCMe)4](BF 4)2 (196.4 mg, 0.5 mmol) in CH 3CN (20 mL), was added dropwise a 54

Me,Me solution of Tpm (149.2 mg, 0.5 mmol) in CH 2Cl 2 (20 mL) with stirring at room temperature. The mixture was allowed to stir overnight and solvents were removed under vacuum to yield a light yellow solid residue. CH 3CN (10 mL) was added to dissolve the solid residue, the solution was allowed to stir for about 10 min, then solvent was removed and the resulting light yellow solid was dried under vacuum overnight. Colorless crystalline material was obtained by vapor diffusion of diethyl ether into a concentrated

Mn solution of 1 in CH 3CN at room temperature. Yield: 291 mg (0.45 mmol, 90%). Anal.

Calc’d. (found) for C 22 H31 B2F8MnN 9: C, 40.65 (40.04); H, 4.81 (4.81); N, 19.39 (18.97).

-1 µeff = 5.90 µ B. FT-IR (KBr, cm ): 2313, ν (C ≡N); 2281, ν (C ≡N).

Me,Me Fe 12 Preparation of [Tpm Fe(NCMe) 3](BF 4)2 (1 ). The light yellow complex

Mn was prepared as for 1 above using [Fe(NCMe)6](BF 4)2 (237.9 mg, 0.5 mmol) and

Me,Me 1 Tpm (149.2 mg, 0.5 mmol). Yield: 321 mg (0.49 mmol, 98%). H NMR (CD 3CN,

295 K; δ, ppm): 55.9 (3H, 4-pz); 46.5 (9H, 3-Me); 14.9 (9H, 5-Me); -58.4 (1H, C-H). µ eff

-1 -1 -1 = 5.87 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM cm ): 863 (6.1). FT-IR (KBr, cm ):

2313, ν (C ≡N); 2283, ν (C ≡N).

Me,Me Co 12 Preparation of [Tpm Co(NCMe) 3](BF 4)2 (1 ). The orange complex was

Mn prepared as for 1 above using [Co(NCCH 3)6](BF 4)2 (239.4 mg, 0.5 mmol) and

Me,Me 1 Tpm (149.2 mg, 0.5 mmol). Yield: 314 mg (0.48 mmol, 96%). H NMR (CD 3CN,

295 K; δ, ppm): 106.5 (1H, C-H); 55.8 (3H, 4-pz); 44.0 (9H, 5-Me); -70.2 (9H, 3-Me).

-1 -1 µeff = 4.99 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM cm ): 467 (32.6), 516 (16.1, sh), 972

(2.8). FT-IR (KBr, cm -1): 2314, ν (C ≡N); 2287, ν (C ≡N). 55

Me,Me Ni Preparation of [Tpm Ni(NCMe) 3](BF 4)2 (1 ). The blue-purple complex was

Mn Me,Me prepared as for 1 above using [Ni(NCMe)6](BF 4)2 (239.3 mg, 0.5 mmol) and Tpm

1 (149.2 mg, 0.5 mmol). Yield: 318 mg (0.486 mmol, 97%). H NMR (CD 3CN, 295 K; δ, ppm): 58.5 (3H, 4-pz); -3.0 (9H, 5-Me); -9.0 (10H, 3-Me + C-H). µ eff = 3.14 µ B. UV-Vis

-1 -1 -1 (CH 3CN, λmax , nm; ε, mM cm ): 581 (16.6), 743 (3.1), 925 (5.5). FT-IR (KBr, cm ):

2319, ν (C ≡N); 2291, ν (C ≡N).

Ph Mn Preparation of [Tpm Mn(NCMe) 3](BF 4)2 (2 ). The light yellow complex was

Mn Ph prepared as for 1 above using [Mn(NCMe)4](BF 4)2 (196.4 mg, 0.5 mmol) and Tpm

(221.3 mg, 0.5 mmol). Yield: 315 mg (0.397 mmol, 79%). Anal. Calc’d. (found) for

C34 H31 B2F8MnN 9: C, 51.42 (50.55); H, 3.93 (3.88); N, 15.87 (15.51). µ eff = 5.94 µ B. FT-

IR (KBr, cm -1): 2308, ν (C ≡N); 2280, ν (C ≡N).

Ph Fe 12 Preparation of [Tpm Fe(NCMe) 3](BF 4)2 (2 ). The light yellow complex was

Mn Ph prepared as for 1 above using [Fe(NCMe)6](BF 4)2 (237.9 mg, 0.5 mmol) and Tpm

1 (221.3 mg, 0.5 mmol). Yield: 390 mg (0.49 mmol, 98%). H NMR (CD 3CN, 295 K; δ, ppm): 47.6 (3H, 4-pz); 27.4 (6H, 3-o-Ph); 12.8 (6H, 3-m-Ph); 5.9 (3H, 3-p-Ph); -4.5 (3H,

-1 -1 5-pz); -53.4 (1H, C-H). µ eff = 5.75 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM cm ): 905

(10.6). FT-IR (KBr, cm -1): 2308, ν (C ≡N); 2282, ν (C ≡N).

Ph Co 12 Preparation of [Tpm Co(NCMe) 3](BF 4)2 (2 ). The orange complex was

Mn Ph prepared as for 1 using [Co(NCMe)6](BF 4)2 (239.4 mg, 0.5 mmol) and Tpm (221.3

1 mg, 0.5 mmol). Yield: 387 mg (0.485 mmol, 97%). H NMR (CD 3CN, 295 K; δ, ppm):

110.8 (1H, C-H); 75.3 (3H, 5-pz); 47.3 (3H, 4-pz); -4.4 (9H, 3-m-Ph + 3-p-Ph); -57.3 56

-1 -1 (6H, 3-o-Ph). µ eff = 4.96 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM cm ): 470 (40.9), 512

(31.4, sh), 992 (2.8). FT-IR (KBr, cm -1): 2315, ν (C ≡N); 2290, ν (C ≡N).

Ph Ni Preparation of [Tpm Ni(NCMe) 3](BF 4)2 (2 ). The blue-purple complex was

Mn Ph prepared as for 1 above using [Ni(NCMe)6](BF 4)2 (239.3 mg, 0.5 mmol) and Tpm

(221.3 mg, 0.5 mmol). Yield: 356 mg (0.445 mmol, 89%). Anal. Calc’d. (found) for

1 C34 H31 B2F8NiN 9: C, 51.18 (50.32); H, 3.92 (4.01); N, 15.80 (16.18). H NMR (CD 3CN,

295 K; δ, ppm): 49.6 (3H, 4-pz); 40.2 (3H, 5-pz); 7.9 (6H, 3-o-Ph); 7.5 (6H, 3-m-Ph); 6.9

-1 -1 (3H, 3-p-Ph); -7.3 (1H, C-H). µ eff = 3.01 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM cm ):

588 (24.4), 972 (5.9). FT-IR (KBr, cm -1): 2318, ν (C ≡N); 2290, ν (C ≡N).

Me,Me Fe Preparation of [Tp Fe(NCMe) 3]BF 4 (3 ). To the solution of

[Fe(NCMe)6](BF 4)2 (237.9 mg, 0.5 mmol) in CH 3CN (20 mL), was added dropwise a

Me,Me solution of TlTp (250.8 mg, 0.5 mmol) in CH 2Cl 2 (20 mL) with stirring at room

temperature. The mixture was allowed to stir overnight, and then solvents were removed

under vacuum. The resulting orange solid was extracted into CH 2Cl 2 (20 mL). The

extracts were then filtered and evaporated to yield an orange solid. After drying the solid

for 2 hours, 10 mL CH 3CN was added to dissolve the solid. Then the resulting orange

solution was stirred for 10 min and solvents were removed under vacuum to yield an

orange solid. Light orange crystals were obtained by vapor diffusion of diethyl ether into

Fe concentrated CH 3CN solution of 3 at room temperature. Yield: 196 mg (0.35 mmol,

1 70%). H NMR (CD 3CN, 295 K; δ, ppm): 57.3 (3H, 4-pz); 48.4 (9H, 3-Me); 16.8 (9H, 5-

-1 -1 Me); -60.6 (1H, B-H). µ eff = 5.62 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM cm ): 478

(93.0), 830 (9.5). FT-IR (KBr, cm -1): 2540, ν (B-H); 2311, ν (C ≡N); 2278, ν (C ≡N). 57

Me,Me Co Preparation of [Tp Co(NCMe) 3]BF 4 (3 ). The orange complex was prepared

Fe Me,Me as for 3 above using [Co(NCMe)6](BF 4)2 (239.4 mg, 0.5 mmol) and TlTp (250.8 mg, 0.5 mmol). The orange complex turned purple after drying under vacuum. Yield: 184

1 mg (0.325 mmol, 65%). H NMR (CD 3CN, 295 K; δ, ppm): 77.9 (1H, B-H); 56.9 (3H, 4- pz); 39.5 (9H, 5-Me); -56.1 (9H, 3-Me). µ eff = 4.80 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM -1 cm -1): 483 (45.7), 503 (45.4, sh), 527 (46.9, sh), 581 (40.3), 621 (29.6, sh), 1021

(10.8). FT-IR (KBr, cm -1): 2526, ν (B-H); 2303, ν (C ≡N); 2277, ν (C ≡N).

Me,Me Ni Preparation of [Tp Ni(NCMe) 3]BF 4 (3 ). The blue complex was prepared as

Fe Me,Me for 3 above using [Ni(NCMe)6](BF 4)2 (239.3 mg, 0.5 mmol) and TlTp (250.8 mg,

0.5 mmol). The blue complex turned green after drying under vacuum. Yield: 175 mg

1 (0.31 mmol, 62%). H NMR (CD 3CN, 295 K; δ, ppm): 63.2 (3H, 4-pz); -2.3 (9H, 5-Me);

-1 - -7.7 (9H, 3-Me); -12.0 (1H, B-H). µ eff = 2.81 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM cm

1): 375 (30.0), 597 (21.3), 757 (4.0), 943 (10.6). FT-IR (KBr, cm -1): 2523, ν (B-H); 2323,

ν (C ≡N); 2298, ν (C ≡N).

Ph,Me Mn Preparation of [Tp Mn(NCMe) 3]BF 4 (4 ). The colorless complex was

Fe Ph,Me prepared as for 3 above using [Mn(NCMe)4](BF 4)2 (196.4 mg, 0.5 mmol) and TlTp

- (343.9 mg, 0.5 mmol). Yield: 286 mg (0.38 mmol, 76%). µ eff = 5.90 µ B. FT-IR (KBr, cm

1): 2550, ν (B-H); 2308, ν (C ≡N); 2280, ν (C ≡N).

Ph,Me Fe Preparation of [Tp Fe(NCMe) 3]BF 4 (4 ). The colorless complex was

Fe Ph,Me prepared as for 3 above using [Fe(NCMe)6](BF 4)2 (237.9 mg, 0.5 mmol) and TlTp

(343.9 mg, 0.5 mmol). Yield: 323 mg (0.43 mmol, 86%). Anal. Calc’d. (found) for

Fe 1 C32 H31 B2F4FeN 7 [4 ·(-CH 3CN) 2]: C, 57.61 (56.12); H, 4.68 (4.94); N, 14.70 (14.40). H 58

NMR (CD 3CN, 295 K; δ, ppm): 55.4 (3H, 4-pz); 29.6 (6H, 3-o-Ph); 21.1 (9H, 5-Me);

10.9 (6H, 3-m-Ph); 6.8 (3H, 3-p-Ph); -56.3 (1H, B-H). µ eff = 5.27 µ B. UV-Vis (CH 3CN,

-1 -1 -1 λmax , nm; ε, mM cm ): 839 (5.4). FT-IR (KBr, cm ): 2548, ν (B-H); 2310, ν (C ≡N);

2281, ν (C ≡N).

Ph,Me Co 13 Preparation of [Tp Co(NCMe) 3]BF 4 (4 ). The orange complex was

Fe Ph,Me prepared as for 3 above using [Co(NCMe)6](BF 4)2 (239.4 mg, 0.5 mmol) and TlTp

(343.9 mg, 0.5 mmol). The orange complex turned dark purple after drying under

1 vacuum. Yield: 300 mg (0.4 mmol, 80%). H NMR (CD 3CN, 295 K; δ, ppm): 69.5 (1H,

B-H); 57.1 (3H, 4-pz); 42.1 (9H, 5-Me); 5.2 (3H, 3-p-Ph); 2.7 (6H, 3-m-Ph); -37.3 (6H,

-1 -1 3-o-Ph). µ eff = 4.82 µ B. UV-Vis (CH 3CN, λmax , nm; ε, mM cm ): 468 (38.4), 519 (48.4),

551 (42.5), 989 (6.7). FT-IR (KBr, cm -1): 2547, ν (B-H); 2314, ν (C ≡N); 2287, ν (C ≡N).

Ph,Me Ni 13 Preparation of [Tp Ni(NCMe) 3]BF 4 (4 ). The blue complex was prepared as

Fe Ph,Me for 3 above using [Ni(NCMe)6](BF 4)2 (239.3 mg, 0.5 mmol) and TlTp (343.9 mg,

0.5 mmol). The blue complex turned green after drying under vacuum. Yield: 240 mg

1 (0.32 mmol, 64%). H NMR (CD 3CN, 295 K; δ, ppm): 63.8 (3H, 4-pz); 8.0 (6H, 3-o-Ph);

7.0 (9H, 3-m-Ph + 3-p-Ph); 1.6 (9H, 5-Me); -10.8 (1H, B-H). µ eff = 2.94 µ B. UV-Vis

-1 -1 -1 (CH3CN, λmax , nm; ε, mM cm ): 605 (21.5), 757 (6.1), 839 (8.1). FT-IR (KBr, cm ):

2546, ν (B-H); 2316, ν (C ≡N); 2290, ν (C ≡N).

Me,Me 19 Preparation of [(Tp )2Mn] . The preparation of the half-sandwich complex

Me,Me [Tp Mn(NCMe)3]BF 4 was unsuccessful, instead, a bis-ligand sandwich complex

Me,Me [(Tp )2Mn] was obtained by using [Mn(NCMe)4](BF 4)2 (196.4 mg, 0.5 mmol) and 59

TlTp Me,Me (250.8 mg, 0.5 mmol). Yield: 139 mg (0.22 mmol, 88%). Anal. Calc’d. (found)

for C 30 H44 B2MnN 12 : C, 55.49 (55.56); H, 6.83 (6.78); N, 25.89 (26.05).

X-ray Crystallographic Analyses. Diffraction-quality crystals of

Ph Mn Ph Ni [Tpm Mn(NCMe) 3](BF 4)2 (2 ), [Tpm Ni(NCMe) 3](BF 4)2•NCMe ( 2 •NCMe),

Me,Me Fe Me,Me [Tp Fe(NCMe) 3](BF 4)•½NCMe ( 3 •½NCMe), [Tp Co(NCMe) 3](BF 4)•½NCMe

Co Ph,Me Fe (3 •½NCMe) and [Tp Fe(NCMe) 3](BF 4)•½NCMe ( 4 •½NCMe) were grown by vapor diffusion of diethyl ether into concentrated CH 3CN solutions. X-ray structural

determinations were performed by Prof. Jeffrey L. Petersen at West Virginia University.

Crystals of appropriate size were washed with perfluoropolyether PFO-XR75 and sealed

under nitrogen in a glass capillary. Each sample was optically aligned on the four-circle

of a Siemens P4 diffractometer equipped with a graphite monochromator, a monocap

collimator, a Mo K α radiation source ( λ = 0.71073 Å), and a SMART CCD detector. The

program SMART (version 5.6) 20 was used for diffractometer control, frame scans,

indexing, orientation matrix calculations, least-squares refinement of cell parameters, and

the data collection. All crystallographic raw data frames were read by the program

SAINT (version 5/6.0) and integrated using 3D profiling algorithms. A semi-empirical

absorption correction was applied using the SADABS routine available in SAINT. 20 The

data were corrected for Lorentz and polarization effects. Data preparation was carried out

by using the program XPREP.20 The structures were solved by a combination of the

Patterson heavy atom method and difference Fourier analysis with the use of SHELXTL

6.1.21 Idealized positions for the hydrogen atoms were included as fixed contributions

using a riding model with isotropic temperature factors set at 1.2 (B-H, methine and 60 aromatic hydrogens) or 1.5 (methyl hydrogens) times that of the adjacent carbon atom.

The positions of the methyl hydrogen atoms were optimized by a rigid rotating group refinement with idealized angles. Both anions in the structure of 2Mn exhibited two-site

disorder ( ca. 0.43:0.57 and 0.27:0.73) involving ca . 60° rotation about one B-F bond. The

B-F bonds and the interatomic F···F separations were constrained to 1.35 ± 0.01 and 2.20

± 0.01 Å, respectively and the anisotropic ellipsoids for the F atoms were refined using

the ISOR option. One anion was similarly disordered in the structure of 2Ni •NCMe, and the lattice NCMe molecule was poorly resolved. The anion was refined using a two-site disorder model ( ca . 0.81:0.19), with the B-F bonds and the interatomic F···F separations

constrained to 1.35 ± 0.02 and 2.15 ± 0.01 Å, respectively; the F atoms of the major site

were refined anisotropically. 2Ni •NCMe is isomorphous to the previously reported iron and cobalt analogs. 3Fe •½NCMe and 3Co •½NCMe are isomorphous; in both lattices the

NCMe molecule was disordered over an inversion center and was treated as a diffuse electron density contribution with the aid of the SQUEEZE routine in the program

PLATON. 22 In 4Fe •½NCMe, the anion exhibited two-site disorder ( ca . 0.55:0.45), and the lattice NCMe molecule was disordered over an inversion center. The B-F bonds, interatomic F···F separations, C ≡N and C-C bonds were constrained to 1.35, 2.10, 1.10

and 1.45 ± 0.01 Å, respectively. The linear absorption coefficient, atomic scattering

factors, and anomalous dispersion corrections were calculated from values found in the

International Tables of X-ray Crystallography. 23 Tables showing crystal and refinement

data are given in Appendices 31-35; thermal ellipsoid plots are shown in Figures 2.1-2.5; relevant bond lengths and angles are listed in Tables 2.1-2.5. 61

Results and Discussion

We prepared and characterized a series of scorpionate ligand supported tris-

M Me,Me acetonitrile complexes [(L)M(NCMe)3](BF 4)n (1 , L = Tpm , M = Mn, Fe, Co, Ni, n

= 2; 2M, L = Tpm Ph , M = Mn, Fe, Co, Ni, n = 2; 3M, L = Tp Me,Me , M = Fe, Co, Ni, n = 1;

4M, L = Tp Ph,Me , M = Mn, Co, Fe, Ni, n = 1), as potential nitrene transfer reaction

Me,Me M Ph M catalysts. [Tpm M(NCMe) 3](BF 4)2 (1 ) and [Tpm M(NCMe) 3](BF 4)2 (2 ; M = Mn,

Fe, Co, Ni) complexes were directly prepared by the treatment of the appropriate metal

II Me,Me salts, [M (NCMe) n](BF 4)2 (n = 4, M = Mn; n = 6, M = Fe, Co, Ni), with Tpm and

Ph Me,Me M Tpm , respectively, using CH 3CN and CH 2Cl 2 as solvents. [Tp M(NCMe) 3]BF 4 (3 ;

Ph,Me M M = Fe, Co, Ni) and [Tp M(NCMe) 3]BF 4 (4 ; M = Mn, Fe, Co, Ni) complexes were

prepared by similar procedures using scorpionate thallium complexes, TlTp Me,Me and

TlTp Ph,Me , repectively (Scheme 2.1). Formation of thermally stable bis-ligand complexes,

R R [(Tpm )2M](BF 4)2 and [(Tp )2M] was prevented by introducing sterically bulky substituents on the 3-position of the pyrazole rings. The using of MeCN coordinated metal salts was also important to limit the formation of bis-ligand complexes. Despite

Me,Me 19 these precautions, the bis-ligand sandwich complex [(Tp )2Mn] was inevitably

Me,Me formed instead of [Tp Mn(NCMe) 3]BF 4. These complexes are so labile as to be stable only in the presence of excess MeCN. With drying under vacuum, significant color changes were observed for complexes 3M and 4M (M = Co, Ni). Elemental analyses on

isolated products were consistent with elimination of MeCN equivalents. Meanwhile,

M M dissolution of complexes 3 and 4 in non-coordinating CH 2Cl 2 also resulted in partial

solvento ligand loss. Edwards and co-workers previously reported the syntheses of 62

Me,Me Ph M M 12 [Tpm M(NCMe) 3](BF 4)2 and [Tpm M(NCMe) 3](BF 4)2 (1 and 2 ; M = Fe, Co),

Ph,Me while Akita and co-workers reported the preparation of [Tp M(NCMe) 3]OTf (M =

13 II 2+ Co, Ni). In addition, crystal structures of [M (NCMe) 6] (M = Mn, Fe, Co, Ni)

precursors have been reported previously. 24-27

Scheme 2.1. Synthesis of complexes 1M-4M (M = Mn, Fe, Co, Ni).

Characterization of [(L)M(NCMe) 3](BF 4)n

A. X-ray Crystallography

The solid-state structures of complexes 2Mn , 2Ni , 3Fe , 3Co and 4Fe were determined

by X-ray crystallography. Attempts to solve the solid state structures of 1Mn and 1Ni failed

- due to structural disorder of the BF 4 counteranion. Crystallographic data collections of

3Ni and 4Mn were also unsuccessful due to loss of lattice solvent. Thermal ellipsoid plots

of the cationic parts of 2Mn , 2Ni , 3Fe , 3Co and 4Fe are shown in Figures 2.1-2.5. Selected metal to nitrogen (M-N) bond distances and angles of 2Mn , 2Ni , 3Fe , 3Co and 4Fe are given in Tables 2.1-2.5. Structure data of 2Mn , 2Ni , 3Fe , 3Co and 4Fe , as well as reported data of

M M 12 Ph,Me M 13 1 -2 (M = Fe, Co), [Tp M(NCMe) 3]OTf (4′ , M = Co, Ni) and metal salts

2+ 24-27 [M(NCCH 3)6] (M = Mn, Fe, Co, Ni) are summarized and compared in Tables 2.6-

2.7 and Figure 2.6.

All complexes show similar core structure with ideal C3v symmetry: the metal

center is sandwiched by a scorpionate ligand in a κ3-coordination fashion and three

MeCN molecules ligated trans to nitrogen donor atoms of the scorpionate ligands. The

M-N bond lengths are consistent with high spin states ( S = 5/2, 2, 3/2, 1, respectively, for

Mn, Fe, Co, Ni). The average M-Npz and M-NNCMe bond lengths decrease in the order

Mn > Fe > Co > Ni, consistent with their ionic radius. The M-Npz bond lengths are significantly correlated with the sterics of the 3-pz substituents: scorpionates bearing phenyl substituents induce longer M-N(pz) bond distances, in the order Tpm Ph > Tp Ph,Me

Me,Me Me,Me > Tpm > Tp . However, the ligand charge has a greater effect on M-NNCMe bond distances than the sterics: the M-NNCMe bond distances of neutral scorpionate supported 64 complexes are shorter than those of complexes supported by anionic scorpionate ligands, in the order Tpm Ph < Tpm Me,Me < Tp Ph,Me < Tp Me,Me (Figure 2.6).

As indicated in Table 2.6, the Npz-M-Npz angles of the neutral scorpionate supported complexes are constrained to a range of 81.0-85.9º by the bite of the Tpm Me,Me and Tpm Ph chelate, while the Npz-M-Npz angles, constrained by the bite of anionic scorpionates Tp Me,Me and Tp Ph,Me , fall in a range of 87.6-88.5º. The C/B-N-N-M torsion

angles are significantly correlated with the sterics of the 3-pz substituent: for Tpm Me,Me supported complexes 1Fe and 1Co , the torsion angles average 11.62 and 9.86º, respectively, while the torsion angles increase to -14.14 and -13.19º in the corresponding

Tpm Ph supported complexes 3Fe and 3Co , respectively. The size of the metal center also affects C/B-N-N-M torsion angles as by comparing 1Fe and 1Co . On the other hand, with the same 3-pz substituents (Tpm Me,Me vs Tp Me,Me ; Tpm Ph vs Tp Ph,Me ), the C ··· M non-

bonded distances of neutral scorpionate complexes are longer than the B ··· M non-bonded

distances of the anionic scorpionate complexes, while with the same ligand, the C/B ··· M distances decrease as the size of the metal ion decreases, in the order of Mn > Fe > Co >

Ni, as seen in the Tpm Ph supported complexes 2M. Overall, the increases of both C/B-N-

N-M torsion angles and C/B ··· M distances are important ways to accommodate larger

metal ions.

As indicated in Table 2.6 and Table 2.7, the M-NNCMe bond lengths of

Ph M [Tpm M(NCMe) 3](BF 4)2 (2 , M = Mn, Fe, Co, Ni), averaging 2.219, 2.151, 2.112 and

2.073 Å, respectively, are comparable to the corresponding M-N bond lengths of metal

2+ salts [M(NCCH 3)6] (2.222, 2.160, 2.114 and 2.071 Å, respectively, for Mn, Fe, Co and 65

Ni). 24-27 However, the M-Npz bond lengths of 2M, averaging 2.297, 2.200, 2.169 and

2+ 2.138 Å, respectively, are all longer than the M-N bond lengths of [M(NCCH 3)6] . This

indicates that the Tpm Ph ligand is a weaker ligand than MeCN. This conclusion affected the catalytic reactivity of 2M, as well as the assignment of 1H NMR spectra of 2M (Figure

2.17), since the ligand dissociates from the metal center even in the presence of MeCN.

In addition, the sterics of the 3-pz substituents have a great effect on the

orientation of the MeCN ligands. The comparison of Tp Me,Me -supported complex 3Fe with

Tp Ph,Me -supported complex 4Fe is depicted in Figure 2.7: the MeCN ligands of 3Fe are

bending toward the Tp Me,Me ligand, with the Fe-N≡C angles averaging 166.5º; while with

Tp Ph,Me as the supporting ligand, the MeCN ligands of 4Fe are bending away from the

Tp Ph,Me ligand, and the Fe-N≡C angles average 176.0º, which is 17.5º smaller than that of

3Fe . Meanwhile, as depicted in Figure 2.7, the sterics of the 3-pz substituents (methyl vs phenyl) of 3Fe and 4Fe force a rotation of the tris-acetonitrile tripod.

Figure 2.1. Thermal ellipsoid plot of the cationic part of 2Mn (30% probability). Hydrogen atoms are omitted for clarity.

Table 2.1. Selected bond distances (Å) and angles (deg) of 2Mn .

Ph Mn [Tpm Mn(NCMe) 3](BF 4)2 (2 )

d(Mn–Npz), Å d(Mn–NNCMe ) , Å Mn(1)-N(1) 2.307(2) Mn(1)-N(7) 2.209(2) Mn(1)-N(3) 2.292(2) Mn(1)-N(8) 2.217(2) Mn(1)-N(5) 2.291(2) Mn(1)-N(9) 2.231(2)

∠Npz–Mn–Npz, deg ∠NNCMe –Mn–NNCMe , deg N(5)-Mn(1)-N(1) 81.90(6) N(7)-Mn(1)-N(8) 90.27(7) N(3)-Mn(1)-N(1) 80.77(6) N(7)-Mn(1)-N(9) 86.01(8) N(5)-Mn(1)-N(3) 80.32(6) N(8)-Mn(1)-N(9) 85.88(8)

∠Npz–Mn–NNCMe (cis ), deg ∠Npz–Mn–NNCMe (trans ), deg N(8)-Mn(1)-N(1) 88.65(7) N(7)-Mn(1)-N(1) 172.26(7) N(9)-Mn(1)-N(1) 101.55(7) N(8)-Mn(1)-N(3) 168.96(6) N(7)-Mn(1)-N(3) 100.64(7) N(9)-Mn(1)-N(5) 172.07(7) N(9)-Mn(1)-N(3) 93.12(7) N(7)-Mn(1)-N(5) 90.81(7) N(8)-Mn(1)-N(5) 101.42(7)

Figure 2.2. Thermal ellipsoid plot of the cationic part of 2Ni (30% probability). Hydrogen atoms are omitted for clarity.

Table 2.2. Selected bond distances (Å) and angles (deg) of 2Ni .

Ph Ni [Tpm Ni(NCMe) 3](BF 4)2 (2 )

d(Ni–Npz) , Å d(Ni–NNCMe ) , Å Ni(1)-N(1) 2.136(2) Ni(1)-N(7) 2.063(2) Ni(1)-N(3) 2.139(2) Ni(1)-N(9) 2.075(3) Ni(1)-N(5) 2.139(2) Ni(1)-N(8) 2.080(2)

∠Npz–Ni–Npz, deg ∠NNCMe –Ni–NNCMe , deg N(1)-Ni(1)-N(3) 86.06(8) N(7)-Ni(1)-N(9) 86.49(10) N(1)-Ni(1)-N(5) 87.05(8) N(7)-Ni(1)-N(8) 87.21(9) N(3)-Ni(1)-N(5) 84.72(8) N(9)-Ni(1)-N(8) 89.78(10)

∠Npz–Ni–NNCMe (cis ), deg ∠Npz–Ni–NNCMe (trans ), deg N(8)-Ni(1)-N(1) 87.73(8) N(7)-Ni(1)-N(1) 173.93(8) N(9)-Ni(1)-N(1) 96.85(9) N(9)-Ni(1)-N(5) 172.80(8) N(7)-Ni(1)-N(3) 99.08(8) N(8)-Ni(1)-N(3) 173.61(9) N(9)-Ni(1)-N(3) 89.50(9) N(7)-Ni(1)-N(5) 90.18(9) N(8)-Ni(1)-N(5) 96.44(9)

Figure 2.3. Thermal ellipsoid plot of the cationic part of 3Fe (30% probability). Hydrogen atoms are omitted for clarity.

Table 2.3. Selected bond distances (Å) and angles (deg) of 3Fe .

Me,Me Fe [Tp Fe(NCMe) 3](BF 4) ( 3 )

d(Fe–Npz), Å d(Fe–NNCMe ), Å Fe(1)-N(1) 2.1423(14) Fe(1)-N(3) 2.232(2) Fe(1)-N(1)#1 2.1423(14) Fe(1)-N(3)#1 2.232(2) Fe(1)-N(1)#2 2.1423(14) Fe(1)-N(3)#2 2.232(2)

∠Npz–Fe–Npz, deg ∠NNCMe –Fe–NNCMe , deg N(1)#1-Fe(1)-N(1)#2 88.45(5) N(3)-Fe(1)-N(3)#1 87.96(7) N(1)#1-Fe(1)-N(1) 88.45(5) N(3)-Fe(1)-N(3)#2 87.96(7) N(1)#2-Fe(1)-N(1) 88.45(5) N(3)#1-Fe(1)-N(3)#2 87.96(7)

∠Npz–Fe–NNCMe (cis ), deg ∠Npz–Fe–NNCMe (trans ), deg N(1)-Fe(1)-N(3) 91.33(6) N(1)-Fe(1)-N(3)#2 179.26(6) N(1)-Fe(1)-N(3)#1 92.26(6)

Figure 2.4. Thermal ellipsoid plot of the cationic part of 3Co (30% probability). Hydrogen atoms are omitted for clarity.

Table 2.4. Selected bond distances (Å) and angles (deg) of 3Co .

Me,Me Co [Tp Co(NCMe) 3](BF 4) ( 3 )

d(Co–Npz), Å d(Co–NNCMe ), Å Co(1)-N(1) 2.116(2) Co(1)-N(3) 2.182(2) Co(1)-N(1)#1 2.116(2) Co(1)-N(3)#1 2.182(2) Co(1)-N(1)#2 2.116(2) Co(1)-N(3)#2 2.182(2)

∠Npz–Co–Npz, deg ∠NNCMe –Co–NNCMe , deg N(1)#1-Co(1)-N(1) 88.35(7) N(3)#2-Co(1)-N(3)#1 87.75(9) N(1)#1-Co(1)-N(1)#2 88.35(7) N(3)#2-Co(1)-N(3) 87.75(9) N(1)-Co(1)-N(1)#2 88.35(7) N(3)#1-Co(1)-N(3) 87.75(9)

∠Npz–Co–NNCMe (cis ), deg ∠Npz–Co–NNCMe (trans ), deg N(1)-Co(1)-N(3) 92.55(8) N(1)-Co(1)-N(3)#1 179.05(8) N(1)-Co(1)-N(3)#2 91.37(8)

Figure 2.5. Thermal ellipsoid plot of the cationic part of 4Fe (30% probability). Hydrogen atoms are omitted for clarity.

Table 2.5. Selected bond distances (Å) and angles (deg) of 4Fe .

Ph,Me Fe [Tp Fe(NCMe) 3](BF 4) ( 4 )

d(Fe–Npz), Å d(Fe–NNCMe ) ), Å Fe(1)-N(1) 2.150(2) Fe(1)-N(7) 2.204(2) Fe(1)-N(3) 2.194(2) Fe(1)-N(8) 2.190(2) Fe(1)-N(5) 2.190(2) Fe(1)-N(9) 2.202(2)

∠Npz–Fe–Npz, deg ∠NNCMe –Fe–NNCMe , deg N(1)-Fe(1)-N(3) 88.50(7) N(8)-Fe(1)-N(9) 87.48(7) N(1)-Fe(1)-N(5) 85.57(6) N(8)-Fe(1)-N(7) 83.13(8) N(5)-Fe(1)-N(3) 90.32(6) N(9)-Fe(1)-N(7) 88.29(7)

∠Npz–Fe–NNCMe (cis ), deg ∠Npz–Fe–NNCMe (trans ), deg N(1)-Fe(1)-N(8) 91.31(7) N(1)-Fe(1)-N(7) 171.55(7) N(1)-Fe(1)-N(9) 97.85(7) N(3)-Fe(1)-N(8) 176.24(6) N(3)-Fe(1)-N(7) 97.46(8) N(5)-Fe(1)-N(9) 176.46(7) N(3)-Fe(1)-N(9) 88.83(7) N(5)-Fe(1)-N(7) 88.41(7) N(5)-Fe(1)-N(8) 93.41(7) 71

Table 2.6. Selected average bond distances (Å) and angles (deg) for tris-acetonitrile complexes.

Compound d(M–Npz), Å d(M–NNCMe ), Å d(C/B ··· M), Å ∠Npz–M–Npz, deg ∠C/B-N–N–M ∠M–N≡C, deg Ref. (torsion, deg) 1Fe 2.165 2.165 3.132 84.9 11.62 168.8 12 1Co 2.125 2.122 3.117 85.4 9.86 170.8 12 2Mn 2.297 2.219 3.261 81.0 5.42 165.3 2Fe 2.200 2.151 3.143 84.5 -14.14 171.0 12 2Co 2.169 2.112 3.127 84.9 -13.19 171.8 12 2Ni 2.138 2.073 3.088 85.9 12.78 171.5 3Fe 2.142 2.232 3.125 88.5 -9.27 166.5 3Co 2.116 2.182 3.120 88.4 -8.82 167.2 4Fe 2.178 2.199 3.131 88.1 -18.13 176.0 4′Co 2.150 2.149 3.137 87.6 -17.22 166.8 13 4′Ni 2.110 2.105 3.107 88.5 17.37 166.2 13

2+ 24-27 Table 2.7. Average M-N bond distances (Å) of metal salts [M(NCCH 3)6] . Compound d(M–N), Å 2+ [Mn(NCCH 3)6] 2.222 2+ [Fe(NCCH 3)6] 2.160 2+ [Co(NCCH 3)6] 2.114 2+ [Ni(NCCH 3)6] 2.071 72

Figure 2.6. Effect s of scorpionate ligands on metal to nitrogen bond lengths.

Figure 2.7. Molecular structures of cationic parts of 3Fe (left) and 4Fe (right) and a space- filling overlay plot of 3Fe and 4Fe (center), emphasizing the steric effects of 3-pyrazole substituents (Me vs . Ph) on the rotation of the MeCN ligands.

Me,Me Fe Table 2.8. Fe-N≡C angles (deg) of complexes [Tp Fe(NCMe) 3]BF 4 (3 ) and Ph,Me Fe [Tp Fe(NCMe) 3]BF 4 (4 ). ∠Fe-N≡C of 3Fe and 4Fe 3Fe 4Fe Fe(1)-N(3)-C(6) 166.53(2) Fe(1)-N(7)-C(31) 176.27(2) Fe(1)-N(3)-C(6) 166.53(2) Fe(1)-N(8)-C(33) 176.11(2) Fe(1)-N(3)-C(6) 166.53(2) Fe(1)-N(8)-C(35) 175.51(2) Average 166.5 Average 176.0 bending toward Tp Me,Me ligand bending away from Tp Ph,Me ligand

B. Electronic Spectroscopy

Strictly speaking, d-d ligand field transitions are forbidden for centrosymmetric

(octahedral) complexes (Laporte selection rule), but relatively weak absorption of

octahedral complexes can occur due to structural distortions and reduction of symmetry. 28

Thus, electronic spectra of complexes 1M-4M (except 3Mn; M = Mn, Fe, Co, Ni) were investigated by UV-Vis spectroscopy. Electronic absorption data are summarized in

M M detail in Tables 2.9-2.11. The UV-Vis spectra of C3v symmetric complexes 1 -4 exhibited electronic absorptions consistent with divalent transition metal ions in ideal octahedral ligand field environments. The electronic absorptions are comparable to those

II of the reported metal salts [M (NCMe) n](BF 4)2 (M = Mn, Fe, Co, Ni) (Table 2.17).

Manganese(II) complexes . According to the d 5 Tanabe-Sugano diagram, there are no spin allowed d-d transitions for high spin Mn(II). 28 Moreover, when a high spin

Mn(II) center is coordinated by an organic ligand, it is rarely possible to identify the weak spin-forbidden d-d transition bands of such a complex, since even the weak UV organic absorption tailing into the visible could obscure them. 28 This effect is seen in featureless spectra of the Mn(II) complexes 1Mn , 2Mn and 4Mn (Figure 2.8), compared with

17 [Mn(NCMe) 4](BF 4)2 (Table 2.17).

Iron(II) complexes . According to the d 6 Tanabe-Sugano diagram, a single spin-

5 5 allowed ( Eg ← T2g ) d-d transition is allowed for high spin Fe(II). The UV-Vis-NIR spectra of the Fe(II) complexes ( 1Fe -4Fe ) exhibit such a band in the range at 839 – 905 nm

(ε = 3.4 – 10.6 M -1 cm -1), see Figure 2.9 and Table 2.9. Additional bands were observed in the visible range at 478 nm ( ε = 93.0 M -1 cm -1) and 580 nm (shoulder, ε = 18.1 M -1 cm -

1) for the Tp Me,Me -supported complex 3Fe . The relatively small extinction coefficient of

the absorption band at 580 nm indicates that it is a d-d transition, while the relatively

6 strong band at 478 is assigned to a Fe → NCCH 3 MLCT. Solutions of high spin d Fe(II)

compounds are commonly colorless, while the MeCN solution of 3Fe shows a visibly

orange color. Therefore, based on the precedent studies of Tpm R supported sandwich octahedral Fe(II) complexes possessing spin-state crossover, 29-31 we propose that this band indicates the presence of low-spin 3Fe in MeCN solution, assigned to the spin-

1 1 31 allowed T1g ← A1g transition (Table 2.9). However, there is no evidence of spin crossover in the solid state of 3Fe , since the Fe-Npz bond lengths of 3Fe average to 2.14 Å

(Table 2.6), consistent with a high spin configuration of the octahedral Fe center, while

32 the typical Fe-N bond distance for low spin octahedral FeN 6 complexes is 1.97 Å.

In order to further elucidate the spin equilibrium of 3Fe , the absorption bands of

3Fe in acetonitrile solution were monitored by UV-Vis spectroscopy at a variety of

temperatures. A moderate bleaching of the absorption band at 478 nm was observed as

the solution temperature was increased from 20-60 ºC (Figure 2.10). This appeared to be

reversible as cooling down the solution to room temperature gave an absorption band

with similar intensity as the measured before heating. This experiment shows an

unambiguous onset of the spin crossover in solution; the conversion from high spin to

low spin is incomplete at this temperature range.

Figure 2.8. UV-Vis spectra of Mn(II) complexes 1Mn (solid gray line), 2Mn (dashed gray Mn line) and 4 (dashed black line) recorded in CH 3CN at 295 K.

Fe Fe Figure 2.9. UV-Vis spectra (CH 3CN, 295 K) of Fe(II) complexes 1 (solid gray line), 2 (dashed gray line), 3Fe (solid black line) and 4Fe (dashed black line).

Table 2.9. UV-Vis spectra data for Fe(II) complexes 1Fe -4Fe . Complex λ, nm ε, M -1 cm -1 Comment Assignment

Me,Me 5 5 [Tpm Fe(CH 3CN) 3](BF 4)2 863 6.1 Eg ← T2g Ph 5 5 [Tpm Fe(CH 3CN) 3](BF 4)2 905 10.6 Eg ← T2g Me,Me 5 5 [Tp Fe(CH 3CN) 3]BF 4 830 9.5 Eg ← T2g 1 1 580 18.1 low spin T1g ← A1g 478 93.0 MLCT Ph,Me 5 5 [Tp Fe(CH 3CN) 3]BF 4 839 5.4 Eg ← T2g

Fe Me,Me Figure 2.10. UV-Vis spectra of 3 [Tp Fe(NCMe) 3]BF 4 in CH 3CN showing the onset of spin crossover behavior.

Cobalt(II) complexes . Typically, the Tanabe-Sugano diagram indicates three spin

7 4 4 4 4 allowed d-d transitions for high spin d Co(II), namely T2g (F) ← T1g (F), A2g ← T1g (F)

4 4 28 Co Co and T1g (P) ← T1g (F). The Co(II) complexes ( 1 -4 ) exhibit a low energy transition

4 4 -1 -1 in the near IR, T2g (F) ← T1g (F), ranging from 970 – 1020 nm ( ε = 2.8 – 10.8 M cm )

(Figure 2.11, Table 2.10). In addition, for each of these four Co(II) complexes, an

asymmetric band with distinct multiple splitting is observed in the visible region ( λmax =

467 – 483 nm; ε = 32.6 – 45.7 M -1 cm -1). The asymmetric structure of this absorption band in the visible region is typical for octahedral Co(II) complexes and cannot be easily assigned. The multiple splitting within the absorption band could arise both from trigonal

2 2 ligand field distortion ( Oh → C3v ), as well as appearance of doublet states ( T1g , T2g ) via

4 4 spin-orbit coupling. In addition, the A2g and T1g (P) excited states are usually close in energy, making the band assignment of high spin Co(II) complexes rather difficult. 28,33-35

Me,Me Co The UV-Vis spectrum of [Tp Co(NCMe) 3]BF 4 (3 ) is shown in Figure 2.12.

Compared with spectra of the other three Co(II) complexes, 3Co shows more splitting.

This may be due to the exceptional trigonal distortion of 3Co indicated by comparison of the average Co–Npz and Co–NNCMe bond distances (Table 2.6).

Nickel(II) complexes . The UV-Vis spectra of tris-acetonitrile Ni(II) complexes

(1Ni -4Ni ) showed spectral features consistent with octahedral coordination of d 8 Ni(II) ion

(Figure 2.13). 28,35-37 The listing of major bands and assignments are given in detail in

Table 2.11. The four Ni(II) complexes (1Ni -4Ni ) all exhibited weak, single absorption bands at 839 – 972 nm ( ε = 5.5 – 10.6 M -1 cm -1) and at 581 – 605 nm ( ε = 16.6 – 24.4 M -1

-1 3 3 3 cm ). They were respectively assigned to the spin allowed T2g(F) ← A2g and T1g (F) ←

3 A2g transitions under parent Oh symmetry, by comparison to [Ni(NCMe) 6](BF 4)2 (Table

2.17).17 Relatively weak peaks at 743 – 757 nm ( ε = 3.1 – 6.1 M -1 cm -1) were observed

Ni Ph for these Ni(II) complexes except for compound 2 , [Tpm Ni(NCMe) 3](BF 4)2. These

1 3 weak shoulder absorption bands can be assigned to the spin forbidden Eg ← A2g transition. 37 A high-energy absorption band of complex 3Ni at 375 nm ( ε = 30.0 M -1 cm -1)

3 3 is assigned to the spin allowed T1g (P) ← A2g transition (Figure 2.14); this high-energy

absorption is usually obscured by UV tailing, as seen for tris-acetonitrile Ni(II)

complexes 1Ni , 2Ni and 4Ni (Figure 2.13).

Co Figure 2.11. UV-Vis spectra (CH 3CN, 295 K) of Co(II) complexes 1 (solid gray line), 2Co (dashed gray line), 3Co (solid black line) and 4Co (dashed black line).

Co Me,Me Figure 2.12. UV-Vis spectrum (CH 3CN, 295 K) of 3 [Tp Co(NCMe) 3]BF 4.

Table 2.10. UV-Vis spectra data for Co(II) complexes 1Co -4Co . Complex λ, nm ε, M -1 cm -1 Assignment

Me,Me 4 4 [Tpm Co(CH 3CN) 3](BF 4)2 972 2.8 T2g (F) ← T1g (F)

516 (sh) 16.1 467 32.6 Ph 4 4 [Tpm Co(CH 3CN) 3](BF 4)2 992 2.8 T2g (F) ← T1g (F)

512 (sh) 31.4 470 40.9 Me,Me 4 4 [Tp Co(CH 3CN) 3]BF 4 1021 10.8 T2g (F) ← T1g (F) 621 (sh) 29.6 581 40.3 527 46.9 503 (sh) 45.4 483 45.7 Ph,Me 4 4 [Tp Co(CH 3CN) 3]BF 4 989 6.7 T2g (F) ← T1g (F) 551 (sh) 42.5 519 48.4 468 38.4

Ni Figure 2.13. UV-Vis spectra (CH 3CN, 295 K) of Ni(II) complexes 1 (solid gray line), 2Ni (dashed gray line), 3Ni (solid black line) and 4Ni (dashed black line).

Ni Me,Me Figure 2.14. UV-Vis spectrum of 3 [Tp Ni(NCMe) 3]BF 4 recorded in CH 3CN at 295 K showing the absorption band assignments.

Table 2.11. UV-Vis spectra data for Ni(II) complexes 1Ni -4Ni . Complex λ, nm ε, M -1 cm -1 Comment Assignment

Me,Me 3 3 [Tpm Ni(CH 3CN) 3](BF 4)2 925 5.5 T2g(F) ← A2g 1 3 743 3.1 Eg ← A2g 3 3 581 16.6 T1g (F) ← A2g 3 3 obscured T1g (P) ← A2g Ph 3 3 [Tpm Ni(CH 3CN) 3](BF 4)2 972 5.9 T2g(F) ← A2g 3 3 588 24.4 T1g (F) ← A2g 3 3 obscured T1g (P) ← A2g Me,Me 3 3 [Tp Ni(CH 3CN) 3](BF 4) 943 10.6 T2g(F) ← A2g 1 3 757 4.0 Eg ← A2g 3 3 597 21.3 T1g (F) ← A2g 3 3 375 30.0 T1g (P) ← A2g Ph,Me 3 3 [Tp Ni(CH 3CN) 3](BF 4) 839 8.1 T2g(F) ← A2g 1 3 757 6.1 Eg ← A2g 3 3 605 21.5 T1g (F) ← A2g 3 3 obscured T1g (P) ← A2g

C. 1H NMR Spectroscopy

Complexes 1M-4M (M = Fe, Co, Ni) all exhibited broad well-resolved 1H NMR

spectra at room temperature in CD 3CN solution, as expected for their paramagnetic high

spin electron configurations ( S = 2, 3/2, 1, respectively, for Fe, Co, Ni; Figures 2.15-

2.18).16 Chemical shifts are summarized in detail in Tables 2.12-2.13.

In an octahedral ligand field, the ground state of the Ni(II) complex is an orbitally

3 nondegenerate A2g state. This state would not be expected to give rise to significant

dipolar (through-space) hyperfine shifts.38 The shifts found for Ni(II) complexes 1Ni -4Ni are dominated by through-bond interaction (contact shift). The C(B)-H, 3-Me (3-Ph) and

5-Me pyrazolyl resonances of complexes 1Ni -4Ni are all close to the diamagnetic region

(5-H pyrazolyl resonance of 3Ni is shifted downfield to 40.2 ppm), while all the 4-H pyrazolyl resonances are significantly shifted downfield to 58.5, 49.6, 63.2 and 63.8 ppm, respectively, indicating the spin is delocalized through the π orbital. On the other hand, the ground states of Fe(II) and Co(II) complexes have holes in t 2g orbitals under an octahedral ligand field; such ground states would give rise to considerable through-space dipolar shift. Therefore, we consider the shifts in Fe(II) complexes 1Fe -4Fe and Co(II) complexes 1Co -4Co to arise from both contact shift and dipolar shift (opposite sign for

Fe(II) and Co(II) complexes). The dipolar effect on the shifts of the Tpm Me,Me ligand of

1Co and 1Fe will be discussed as examples. Compared with the shift pattern of 1Ni , the C-

H resonance for 1Co is significantly downfield to 106.5 ppm, the 5-Me resonance is also downfield to 44.0 ppm, while the 3-Me resonance is shifted upfield to -70.2 ppm.

However, the 4-H pyrazolyl resonance is barely shifted compared with that of 1Ni ,

resonating at 55.8 ppm. Based on literature precedent, a three-dimensional double-cone

graph can be used to interpret the shift pattern of 1Co (Figure 2.19).38-43 The direction of the double-cone (z axis of the magnetic field) is along the H-C··· Co axis. The 5-Me and

C-H protons are always in the positive section of the double cone, therefore, these resonances are significantly shifted to downfield area. The 3-Me protons are in the negative section, shifting the resonance at upfield. On the other hand, the overall dipolar shifting of 1Fe is reversed, making the C-H proton fall upfield, while the 3-Me and 5-Me

protons fall downfield. 39,41

In addition, resonances of free Tpm Ph ligand protons were observed in the 1H

NMR spectra of the Tpm Ph -supported complexes 2M (M = Fe, Co, Ni). After carefully comparing the M-Npz bond lengths of 2M with the M-N bond lengths of the corresponding metal salts, [M(NCMe) 6](BF 4)2, we found that the average M-Npz bond lengths of 2M are longer than the M-N bond lengths of the corresponding metal salts

Ph (Figure 2.6). Therefore, dissociation of the weakly coordinated Tpm ligand in CD 3CN solution was observed in the 1H NMR spectra of 2M (Figure 2.17).

Table 2.12. Chemical shifts for Tpm Me,Me and Tp Me,Me -supported complexes 1M and 3M

(M = Fe, Co, Ni) recorded in CD 3CN at 295 K. Me,Me M Me,Me M Tpm (δ, ppm) (1 ) Tp (δ, ppm) (3 ) Proton position Fe Co Ni Fe Co Ni 4-H 55.9 55.8 58.5 57.3 56.9 63.2 3-Me 46.5 -70.2 -9.0 48.4 -56.1 -7.7 5-Me 14.9 44.0 -3.0 16.5 39.5 -2.3 C-H -58.4 106.5 -9.0 – – – B-H – – – -60.6 77.9 -12.0

Table 2.13. Chemical shifts for Tpm Ph and Tp Ph,Me -supported complexes 2M and 4M (M =

Fe, Co, Ni) recorded in CD 3CN at 295 K. Tpm Ph (δ, ppm) (2M) Tp Ph,Me (δ, ppm) (4M) Proton Fe Co Ni Fe Co Ni position 4-H 47.6 47.3 49.6 55.4 57.1 63.8 3-Ph, para 5.9 -4.4 6.9 6.8 5.2 7.0 3-Ph, meta 12.8 -4.4 7.5 10.9 2.7 7.0 3-Ph, ortho 27.4 -57.3 7.9 29.6 -37.6 8.0 5-H -4.5 75.3 40.2 – – – C-H -53.4 110.8 -7.3 – – – 5-Me – – – 21.1 42.1 1.6 B-H – – – -56.3 69.5 -10.8

H Me Me C N 5 Me N H N H N 4 N H N 3 Me Me M Me N N Me N Me

1 Me,Me Fe Co Figure 2.15. H NMR spectra (CD 3CN, 295 K) of Tpm -supported complexes 1 , 1 Ni and 1 . Peaks due to CH 3CN are marked “s”; lattice solvents (CH 2Cl 2) are denoted with an asterisk (*).

H Me Me B N 5 Me N H N H N 4 N H N 3 Me Me M Me N N Me N Me

1 Me,Me Fe Co Figure 2.16. H NMR spectra (CD 3CN, 295 K) of Tp -supported complexes 3 , 3 Ni and 3 . Peaks due to CH 3CN are marked “s”; lattice solvents (CH 2Cl 2) are denoted with an asterisk (*).

H H H C N 5 H N H N H N 4 N H N 3 Ph H M H M Ph N N N Me H Me

H Me H

1 Ph Fe Co Figure 2.17. H NMR spectra (CD 3CN, 295 K) of Tpm -supported complexes 2 , 2 Ni and 2 . Peaks due to CH 3CN are marked “s”; lattice solvents (CH 2Cl 2) are denoted with an asterisk (*); resonances of free Tpm Ph ligand are denoted as Tpm Ph .

H Me Me B N 5 Me N H N H N 4 N H N 3 Ph H M H M Ph N N N Me H Me

H Me H

1 Ph,Me Fe Co Figure 2.18. H NMR spectra (CD 3CN, 295 K) of Tp -supported complexes 4 , 4 Ni and 4 . Peaks due to CH 3CN are marked “s”; lattice solvents (CH 2Cl 2) are denoted with an asterisk (*).

Figure 2.19. Graphical representation of complex 1Co in a dipolar double cone.

D. FT-IR Spectroscopy

Complexes 1M-4M (M = Mn, Fe, Co, Ni) were all characterized by infrared spectroscopy using KBr as a matrix (Figures 2.20-2.23). The results are summarized in

Tables 2.14-2.15. The κ3 coordination fashion of Tp R ligands of 3M-4M was confirmed by

-1 16,44 M M the νB-H absorptions in the range of 2523 – 2550 cm . The IR spectra of 1 -4

-1 -1 display two νCN bands in a range of 2278 – 2298 cm and 2303 – 2323 cm , respectively, with medium intensity. Absorptions in this spectral region are typical for coordinated

MeCN. The two νCN absorptions can be straightforwardly assigned to the fundamental ν2-

CN stretching mode and the combination mode (ν3 + ν4), similar to the assignment of free

45,46 MeCN. The νCN absorptions are also comparable to those of known metal salts,

II 17,46 [M (NCMe) n](BF 4)2 (n = 4, M = Mn; n = 6, M = Fe, Co, Ni) (Table 2.17). The emergence of two absorption bands of MeCN is due to the Fermi resonance between the

47 ν2-CN fundamental band and the ν3 + ν4 combination bands. The presence of additional

Ni νCN absorption bands for 3 is presumably owing to the presence of a second Ni(II)

species due to the solvento loss of 3Ni (Figure 2.22).

Without exception, the energies of the two νCN absorptions for the coordinated

MeCN of complexes 1M-4M (M = Mn, Fe, Co, Ni) are higher than those of the free MeCN

(2253 cm -1 and 2293 cm -1). This is presumably because: the nitrogen atom long pair of the nitrile has some C-N σ-antibonding character; the donation of this electronic density

to an empty orbital of a metal ion will strengthen the C-N σ-bond, thus increasing the stretching frequency of C ≡N. 48 With complexes 1M-4M (M = Mn, Fe, Co, Ni), the

energies of both νCN absorption bands increase from Mn to Ni: the two νCN absorptions of

4M (M = Mn, Fe, Co, Ni) increase from 2280 cm -1 to 2290 cm -1, and from 2308 cm -1 to

2316 cm -1, respectively, as the metal center changes from Mn to Ni. This trend qualitatively coordinates with the ligand field stabilization energy of Mn to Ni. 45 This observation further supports the discussion above that the increase of the stretching frequency of CN is due to σ donation of electron density from the nitrogen atom long pair of nitrile. On the other hand, the scorpionate ligands show much less of an effect on the stretching frequency of CN than the metal ions, as indicated by the comparison of νCN absorption bands of 2Ni and 4Ni (Figure 2.24).

M M Me,Me Table 2.14. FT-IR νCN absorption bands of [(L)M(NCMe)3](BF 4)2 (1 -2 ; L = Tpm , TpmPh ; M= Mn, Fe, Co, Ni) as KBr pellets. Me,Me M Ph M Tpm (1 ) Tpm (2 ) Metal ion -1 -1 νCN , cm νCN , cm Mn 2313 2281 2308 2280 Fe 2313 2283 2308 2282 Co 2314 2287 2315 2290 Ni 2319 2291 2318 2290

M M Table 2.15. FT-IR νCN and νB-H absorption bands of [(L)M(NCMe)3]BF 4 (3 -4 ; L = Tp Me,Me , Tp Ph,Me ; M= Mn, Fe, Co, Ni) as KBr pellets. Tp Me,Me (3M) Tp Ph,Me (4M) -1 -1 -1 -1 Metal ion νB-H, cm νCN , cm νB-H, cm νCN , cm Mn – – – 2550 2308 2280 Fe 2540 2311 2278 2548 2310 2281 Co 2526 2303 2287 2547 2314 2287 Ni 2523 2323 2298 2546 2316 2290

Me,Me M Figure 2.20. FT-IR spectra of [Tpm M(NCMe)3](BF 4)2 (1 , M = Mn, Fe, Co, Ni) showing the νCN absorption bands.

Ph M Figure 2.21. FT-IR spectra of [Tpm M(NCMe)3](BF 4)2 (2 , M = Mn, Fe, Co, Ni) showing the νCN absorption bands.

Me,Me M Figure 2.22. FT-IR spectra of [Tp M(NCMe) 3]BF 4 (3 , M = Fe, Co, Ni) showing the νCN and νB-H absorption bands.

Ph,Me M Figure 2.23. FT-IR spectra of [Tp M(NCMe)3]BF 4 (4 , M = Mn, Fe, Co, Ni) showing the νCN and νB-H absorption bands.

100

Ph Ni Figure 2.24. FT-IR spectra of [Tpm Ni(NCMe)3](BF 4)2 (2 , solid line) and Ph,Me Ni [Tp Ni(NCMe)3]BF 4 (4 , dashed line), emphasizing the effect of ligand on the νCN absorption bands.

101

E. Magnetic Properties

The room temperature effective magnetic moments of complexes 1M-4M (M =

Mn, Fe, Co, Ni) were determined in CD 3CN solution at room temperature by the Evans

18 NMR method. The results are summarized in Table 2.16. The observed µeff values of

Mn Mn Mn tris-acetonitrile Mn(II) complexes 1 , 2 and 4 are in a range of 5.90 - 5.94 µB,

49 consistent with the expected spin only value ( S = 5/2, 5.92 µB). These values are also

17 comparable with 5.90 µB, reported for [Mn(NCMe) 4](BF 4)2 (Table 2.17). The observed

Fe Fe µeff values of neutral scorpionate ligand supported Fe(II) complexes 1 and 2 and

Co Co Co(II) complexes 1 and 2 are 5.87 µB, 5.75 µB, 4.99 µB and 4.96 µB, respectively, while for anionic scorpionate ligand coordinated Fe(II) complexes 3Fe and 4Fe and Co(II)

Co Co complexes 3 and 4 , the observed moments are 5.62 µB, 5.27 µB, 4.80 µB and 4.82 µB,

respectively. These Fe(II) and Co(II) complexes all have µ eff values exceeding the spin

II II only values (Fe : S = 2, 4.90 µB; Co : S = 3/2, 3.87 µB), but are within the range of what

is commonly observed for octahedral Fe(II) and Co(II) complexes. 49,50 They are also

comparable with 5.59 µB and 5.18 µB, reported for [Fe(NCMe) 6](BF 4)2 and

17 [Co(NCMe) 6](BF 4)2, respectively (Table 2.17). The neutral scorpionate ligand

supported Fe(II) and Co(II) complexes have higher observed µeff values than the

corresponding anionic scorpionate ligand supported analogues. This trend is also true for

Ni Ni the Ni(II) complexes 1 -4 , wherein the observed moments are 3.14 µB, 3.01 µB, 2.81 µB and 2.94 µB, respectively. These observed values are slightly less than the reported value

for [Ni(NCMe) 6](BF 4)2 (3.22 µB), but are still in good agreement with the spin only

17,49 values for two unpaired electrons ( S = 1, 2.83 µB).

102

M M Table 2.16. Effective magnetic moments (µeff ) of complexes 1 -4 (M = Mn, Fe, Co, Ni) in CD 3CN at 295 K by Evans NMR method.

Complexes Spin µeff , µB µeff , µB µeff , µB Multiplicity (observed) (typical values) (spin only)

1Mn 5/2 5.90 5.6 – 6.1 5.92

1Fe 2 5.87 5.0 - 5.9 4.90

1Co 3/2 4.99 4.7 - 5.5 3.87

1Ni 1 3.14 2.8 – 3.5 2.83

2Mn 5/2 5.94 5.6 – 6.1 5.92

2Fe 2 5.75 5.0 - 5.9 4.90

2Co 3/2 4.96 4.7 - 5.5 3.87

2Ni 1 3.01 2.8 – 3.5 2.83

3Fe 2 5.62 5.0 - 5.9 4.90

3Co 3/2 4.80 4.7 - 5.5 3.87

3Ni 1 2.81 2.8 – 3.5 2.83

4Mn 5/2 5.90 5.6 – 6.1 5.92

4Fe 2 5.27 5.0 - 5.9 4.90

4Co 3/2 4.82 4.7 - 5.5 3.87

4Ni 1 2.94 2.8 – 3.5 2.83

103

II Table 2.17. UV-Vis, Magnetic Susceptibility and FT-IR data for [M (NCMe) n](BF 4)2 (n = 4, M = Mn; n = 6, M = Fe, Co, Ni) (literature values).17

II -1 -1 -1 M ν(CN), cm µeff , µB. λ, nm ε, M cm Assignment

4 6 Mn 2312(m), 2284(m) 5.90 536 0.3 T1g (G) ← A1g 4 6 408 1.2 Eg(G) ← A1g Fe 2310(m), 2287(m) 5.59 5 5 912 2.8 Eg ← T2g Co 2316(m), 2292(m) 5.18 a 4 4 1017 3.2 T2g (F) ← T1g (F)

492 11.3

476 11.0 Ni 2316(m), 2292(m) 3.22 3 3 958 3.1 T2g(F) ← A2g 3 3 582 2.5 T1g (F) ← A2g 3 3 358 10.8 T1g (P) ← A2g

Infrared: Samples were prepared as nujol mulls placed between KBr plates. UV-Vis: MeCN was used as solvent. a Data was recorded by SL.

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108

CHAPTER 3: NITRENE TRANSFER CATALYSIS MEDIATED BY TRANSITION

METAL SCORPIONATE COMPLEXES

Transition metal catalyzed nitrene transfer reactions are among the most attractive

methodologies for the syntheses of valuable nitrogen-containing compounds such as

aziridines and amines. 1-5 Various transition metals including manganese, 6-8 cobalt, 9 copper, 4,10,11 silver, 4,12,13 gold, 14,15 ruthenium, 16 and rhodium 17 complexes have been shown to induce these transformations. Among them, copper- or rhodium-mediated aziridination and amination reactions are the well-established protocols for C-N bond formation. However, precious or toxic metals are commonly involved in these reactions.

In contrast, earth-abundant 3d metals are inexpensive and may be more biocompatible, yet have received sparse attention as potential practical catalysts for olefin aziridination or C-H bond amination.

Mansuy and co-workers were the first to report an iron catalyzed intermolecular alkene aziridination using [Fe(TTP)Cl] as catalyst and PhI=NTs as a nitrene precursor. 6

A disparate range of iron complexes induce the conversion of alkenes to the corresponding aziridines: Hossian’s Lewis acidic iron(II) complex, [( η5-

18 C5H5)Fe(CO) 2(THF)]BF 4; Latour’s mixed-valent diiron complex bearing a hexadentate phenol ligand; 19 Zhou’s iron phthalocyanine complex; 20 Halfen’s polyamine ligands

21 22 supported iron complexes; Che’s iron complex [Fe(Cl 3terpy) 2] and Bolm’s Fe(OTf) 2 systems. 23 More recently, Jenkins and co-workers also observed catalytic reactivity using a macrocyclic tetracarbene iron complex, which catalyzed the aziridination of a wide variety of aliphatic alkenes with aryl azides. 24

109

On the other hand, iron-mediated C-H bond amination reactions are less well

developed than the analogous olefin aziridinations. Breslow and co-workers reported the

first example of an iron complex induced nitrene C-H bond insertion. [Fe(TTP)Cl]

catalyzed the conversion of cyclohexane to cyclohexane sulfonamide with only 3.1%

yield. 25 Zhou and co-workers have shown that iron phthalocyanine is capable of

catalyzing intermolecular amination of organic substrates containing benzylic, tertiary or

allylic C-H bonds, 20 while Che and co-workers evaluated the intramolecular C-H bond

nitrene insertion reactions of sulfamate esters and PhI(OAc) 2 with the iron complex

22 [Fe(Cl 3terpy) 2]. Recently, Betley and co-workers reported the first isolated iron(III)-

Ar t imido complex ( L)Fe(N( p- BuC 6H4)Cl that is able to transfer the imido moiety to benzylic C-H bond of toluene. 26

In the pursuit of efficient and inexpensive transition metal catalysts for C-N bond

formation reactions, we employ the scorpionate ligand-supported tris-acetonitrile metal

M Me,Me M complexes [(L)M(NCMe)3](BF 4)n (1 , L = Tpm , M = Mn, Fe, Co, Ni, n = 2; 2 , L =

Tpm Ph , M = Mn, Fe, Co, Ni, n = 2; 3M, L = Tp Me,Me , M = Fe, Co, Ni, n = 1; 4M, L =

Tp Ph,Me , M = Mn, Co, Fe, Ni, n = 1) as catalysts for the aziridination of alkenes and amination of C-H bonds of hydrocarbons in the present work. The inspiration for our investigation is the scorpionate-supported Cu(I) complexes recently employed by Pérez and co-workers as a family of efficient metal catalysts for the aziridination of olefins and

C-H bond amination reactions of inert hydrocarbons.4,27,28 Our scorpionate-supported metal complexes 1M-4M might exhibit similar reactivities toward olefin C=C bond aziridination, as well as aromatic and benzylic C-H bond amination.

110

Aziridination Reactions of Olefins

We presented the synthesis and characterizations of 1M-4M (M = Mn, Fe, Co, Ni) in the previous chapter. In our initial investigation of reactivity, scorpionate complexes

M M 1 -4 as well as the Fe(II) salt [Fe(NCMe) 6](BF 4)2 were examined as potential catalysts for the aziridination of styrene using PhI=NTs as nitrene precursor. In all cases, the reactions were carried out at room temperature using 5 mol% metal catalyst and a styrene to PhI=NTs (0.2 mmol) ratio of 5:1. The results are summarized in Table 3.1. It was found that the Fe(II) complexes gave the desired aziridine 2 in good yield ranging from

51% to 94%, with complete consumption of PhI=NTs in less than 5 min (Table 3.1,

entries 2, 6, 9, 13). Interesting, when Tpm Ph or Tp Ph,Me (bearing phenyl substituents on 3-

position of pyrazole rings) coordinated Fe(II) complexes (2Fe , 4Fe ) were used as catalyst,

the yield of the aziridine 2 was found to be much lower than those of the analogous Fe(II)

complexes 1Fe and 3Fe supported by Tpm Me,Me and Tp Me,Me ligands (bearing methyl substituents on 3-position of pyrazole rings), respectively. This is presumably due to the intramolecular aromatic C-H bond amination of the phenyl groups on the ligands, 29-31 which in turn, lowers the catalytic activities of these metal catalysts. The desired aziridine product 2 was also obtained when Mn(II), Co(II) or Ni(II) analogues were introduced as

nitrene transfer catalyst, although the yields were much lower than those of Fe(II)

analogues (Table 3.1). Therefore, among the various metal catalysts summarized in Table

Me,Me Fe 3.1, [Tpm Fe(NCMe) 3](BF 4)2 (1 ) was found to be the most efficient catalyst for the aziridination reaction of styrene with PhI=NTs.

111

M M Table 3.1. Complexes 1 -4 and [Fe(CH 3CN) 6](BF 4)2 catalyzed aziridination of styrene with PhI=NTs.

Entry Catalyst Reaction time Yield (%) a Me,Me 1 [Tpm Mn(CH 3CN) 3](BF 4)2 120 min 18

Me,Me b 2 [Tpm Fe(CH 3CN) 3](BF 4)2 30 min 94

Me,Me 3 [Tpm Co(CH 3CN) 3] (BF 4)2 60 min 19

Me,Me 4 [Tpm Ni(CH 3CN) 3](BF 4)2 120 min 16

Ph 5 [Tpm Mn(CH 3CN) 3](BF 4)2 100 min 17

Ph b 6 [Tpm Fe(CH 3CN) 3](BF 4)2 30 min 63

Ph 7 [Tpm Co(CH 3CN) 3](BF 4)2 40 min 30

Ph 8 [Tpm Ni(CH 3CN) 3](BF 4)2 100min 16

Me,Me b 9 [Tp Fe(CH 3CN) 3]BF 4 30 min 89

Me,Me 10 [Tp Co(CH 3CN) 3]BF 4 60 min 42

Me,Me 11 [Tp Ni(CH 3CN) 3]BF 4 140 min 30

Ph,Me 12 [Tp Mn(CH 3CN) 3]BF 4 120 min 18

Ph,Me b 13 [Tp Fe(CH 3CN) 3]BF 4 30 min 51

Ph,Me 14 [Tp Co(CH 3CN) 3]BF 4 60 min 42

Ph,Me 15 [Tp Ni(CH 3CN) 3]BF 4 120 min 15

16 [Fe(CH 3CN) 6](BF 4)2 30min --

c 17 [Fe(CH 3CN) 6](BF 4)2 30min 71 Ratio of substrate to PhINTs is 5:1. a Isolated yield. b Complete dissolution of PhINTs is less than c 5 min. CH 3CN as solvent.

112

Encouraged by these results, we then further optimized the catalytic activity of the

Me,Me Fe iron(II) complex [Tpm Fe(NCMe) 3](BF 4)2 (1 ) toward the aziridination reaction of

styrene with PhI=NTs in CH 2Cl 2 at room temperature. Without catalyst, no aziridine product was observed even after 24 h, as indicated in Figure 3.1 and Table 3.2 (entry 1).

Fe When 0.5 mol% 1 was loaded with the same amount of styrene and PhI=NTs (5:1

ratio), the conversion of styrene to 2-phenyl-N-tosylaziridine 2 was achieved in 62%

yield (Table 3.2, entry 2). However, the yield of aziridine 2 dropped to only 33% with 1.0

equivalent of styrene relative to PhI=NTs (Table 3.2, entry 3). The best result (94% yield)

was obtained when 5 mol% of 1Fe was used with a styrene to PhI=NTs mole ratio of 5:1

(Table 3.2, entry 5). Such a degree of conversion achieved by 1Fe exceeds those previous described for Fe(II) mediated aziridination of styrene with PhI=NTs, 6,18,20,21 and it is also

better than the aziridination of styrene using the analogous Cu(I) catalyst

R 28 [Tpm Cu(NCMe)]BF 4 in ionic liquid reported by Pérez and co-workers. Notably, the

solid nitrene precursor PhI=NTs was consumed in less than 5 min, which is much faster

than reported metal mediated aziridinations, except for an analogous aziridination

21 reported by Halfen and co-workers, with the Fe(II) complexes [(Me 5dien)Fe(OTf)2] and

[(iPr 3TACN)Fe(OTf) 2] as catalysts. With the same styrene to PhI=NTs mole ratio (5:1), a reasonable yield of aziridine 2 was still obtained when only 1 mol% of 1Fe was used

(Table 3.2, entry 4).

113

8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 δ (ppm) Figure 3.1. 1H NMR spectra of aziridination of styrene with PhI=NTs (ratio of 5:1; Fe CDCl 3, 295 K): (A), without catalyst 1 , no aziridine product was observed after 24 h; (B), with 5 mol% of 1Fe , observation of aziridine product; (C), pure aziridine. Peaks due to residual solvent are marked “*”.

114

Me,Me Fe Table 3.2. [Tpm Fe(NCMe) 3](BF 4)2 (1 ) catalyzed aziridinations of styrene with PhI=NTs.

Entry substrate a mol.% cat. b Reaction time Yield (%) d

1 5 0 24 h 0

2 5 0.5 60 min f 62

3 1 0.5 120 min e 33

4 5 1 30 min c 75

5 5 5 30 minc 94

6 5 10 30 min c 85 a Number of equiv. of substrate to PhINTs. b vs. PhINTs. c Complete dissolution of PhINTs is less than 5 min. d Isolated yield, 100% conversion of PhINTs. e PhINTs was completely dissolved in about 2 hours. f PhINTs was completely dissolved in 50 min.

115

Other nitrene precursors, such as tosylazide, chloramines-T and PhI=NNs, were

Fe also tested for the aziridination of styrene using 1 as catalyst. Among them, TsN 3 did not exhibit any significant nitrene transfer reactivity at room temperature, while NaClNTs and PhI=NNs led to the formation of unidentified products. Aziridination of styrene using a phenyliodinane generated in situ was also studied. Thus, the reaction using 5 mol% of

Fe 1 and a combination of TsNH 2 5 and PhI(OAc) 2 6 as a potential nitrene source

proceeded smoothly, affording 2-phenyl-N-tosylaziridine 2 in 42% yield (Scheme 3.1).

Ts N O O [Tpm*Fe(CH CN) ](BF ) (5 mol%) S 3 3 4 2 NH2 CH3CN, rt, 18h, PhI(OAc)2 (6) 2 42% 1 5 O O S in situ formation of nitrene precursor N I

Scheme 3.1. Azirdination of styrene using TsNH 2 5 and PhI(OAc) 2 6 as nitrene source Me,Me Fe catalyzed by [Tpm Fe(CH 3CN) 3](BF 4)2 (1 ).

116

Having optimized the reaction conditions, the scope of olefin substrates was

further extended. Various other olefins 7-11 were examined for catalytic aziridination

using the most active complex 1Fe as catalyst. As summarized in Table 3.3, moderate to good isolated yields (46-94%) of aziridine products were typically obtained at room

Fe temperature in CH 2Cl 2, using 5 mol% of 1 and an olefin to PhI=NTs ratio of 5:1, with

complete consumption of PhI=NTs observed within 5 min. The use of styrene 1 led to

excellent yield of the corresponding aziridine 2 (Table 3.3, entry 1; Appendix 1).

Cyclohexene 7 and norbornene 8, as well as electron deficient trans -methyl cinnamate 11

also afforded moderate yields of the corresponding aziridines (Table 3.3, entries 2, 3, 6;

Appendices 7, 9, 4). When cyclohexene 7 was used, both the olefin aziridination product

12 (Appendix 7) and allylic C-H bond amination product 13 (Appendix 8) were observed

in 49% and 34% isolated yields, respectively. Notably, the aziridination reaction of trans -

stilbene 10 gave no observed aziridine product; instead, an olefinic C-H bond amination

product 16 was isolated in 51% yield (Table 3.3, entry 5; Appendix 6), which was

confirmed by 1H, 13 C and COSY NMR spectra (Appendix 6). Aziridination of cis- stilbene 9 led to the formation of a mixture of the aziridination product 15 (Appendix 5) and the olefinic C-H bond amination product 16 in 2.5:1 ratio with 79% total yield (Table

3.3, entry 5). To the best of our knowledge, this is the first example of nitrene insertion into the olefinic C-H bond of cis - or trans - stilbene. 32

117

Me,Me Fe Table 3.3. Olefin aziridinations mediated by [Tpm Fe(NCMe) 3](BF 4)2 (1 ) with PhI=NTs. Entry substrate a Reaction time b aziridines Yield (%) c

1 30 min 94

NHTs

2 30 min NTs , 49, 34

12 13

3 30 min 51 NTs 14

4 30 min , 57, 22 NTs 15

H 5 30 min 51

NHTs 16

6 30 min 46 CO2Me NTs 17 a Substrate to PhINTs is 5:1 b Complete dissolution of PhINTs in 5 min. c Isolated yield.

118

Aziridination of para -Substituented Styrenes

The relative rates of aziridination of a series of para -substituted styrenes ( p-X-

C6H4CH 2=CH; X = Me, H, Cl, CF 3, NO 2) were examined through competition

experiments. The experiments were conducted under reaction conditions in which a

mixture of equal amounts of styrene (0.2 mmol) and a para -substituted analog (0.2 mmol) was treated with PhINTs (0.2 mmol) for a period of 30 min at room temperature

Fe 1 in CH 3CN, using 1 (5 mol%) as catalyst (Scheme 3.2). A H NMR example is shown in

Figure 3.3. The results are summarized in Table 3.4. A logarithmic plot of the quotient of

+ + yields vs the Hammett parameter σp yields a linear relationship, from which a value of ρ

= -0.93 is derived from the slope as indicated in Figure 3.2. The results reveal that styrenes with electron-donating substituents are more reactive than unsubstituted styrene toward aziridination reaction, while electron-withdrawing substituents retard rates of aziridination. The observed ρ+ value of -0.93 is comparable to that aziridination reactions

VI + 16 of [Ru (TPP)(NTs) 2] ( ρ = -1.1) reported by Che and co-workers, and it is 3.3-fold

Me,Me + larger in magnitude than styrene aziridination catalyzed by [Tp Cu(C 2H4)] ( ρ =

-0.28), reported by Pérez and co-workers. 33 Overall, the large negative ρ+ value reveals that the aziridination reaction catalyzed by 1Fe is highly sensitive to the electronic effect

of the para -substituent of styrene; thus, an electrophilic intermediate, plausibly high

valent iron(IV)-imido complex, is involved in the aziridination reactions catalyzed by

Me,Me Fe 22 [Tpm Fe(NCMe) 3](BF 4)2 (1 ).

119

Scheme 3.2. Competition reaction of styrene and para -substituted styrene mediated by Me,Me Fe [Tpm Fe(NCMe) 3](BF 4)2 (1 ) with PhI=NTs.

Table 3.4. Experimental kY/kH and log(kY/kH) values.

X σp kY/kH log(kY/kH) Me -0.17 2.2951 0.3608 H 0 1 0 Cl 0.23 1.3204 0.1207 CF 3 0.54 0.3544 -0.4505 NO 2 0.78 0.2876 -0.5412

0.6

0.4 Me y = -0.9(2)x + 0.15(9) R² = 0.8809 0.2 Cl

H 0 H /k Y k

log -0.2

-0.4 CF 3 NO 2 -0.6

-0.8 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 σp

Figure 3.2. Hammett plot of experimentally determined log(kY/kH) value vs . Hammett para -substituent constant σp.

120

8.15 8.12 7.87 7.84 7.33 7.28 7.26 7.24 7.21 7.20 7.19 6.79 3.84 3.83 3.82 3.81 3.78 3.76 3.76 3.74 3.04 3.02 2.98 2.95 2.43 2.42 2.38 2.36 2.26 0.72 2.03 0.45 0.36 8.21 2.28 1.00 0.27 0.71 3.93 1.55 7.35

1 Figure 3.3. H NMR spectrum (CDCl 3, 295 K): Competition reaction of styrene and p- Me,Me Fe nitrostyrene mediated by [Tpm Fe(NCMe) 3](BF 4)2 (1 ) with PhI=NTs; mesitylene (0.1 mmol) as internal standard.

121

C-H bond Amination of Tetrahydrofuran

Encouraged by the results found for aziridination reactions of cyclohexene 7 and

Me,Me Fe trans-stilbene 10 using [Tpm Fe(NCMe) 3](BF 4)2 (1 ) as catalyst, in which nitrene

insertion into a C-H bond was observed, we then decided to examine the reactivity of

M M complexes 1 -4 , as well as metal salts [M(NCMe) 6](BF 4)2 (M = Mn, Fe, Co, Ni) toward the amination of tetrahydrofuran 18 . In a typical reaction, PhI=NTs (0.2 mmol) was reacted with THF 18 (1 mL) at room temperature in CH 3CN, in the presence of metal catalyst (5 mol%) and 4 Å molecular sieves. The conversion yield of THF 18 to N-

(tetrahydro-2-furanyl)-toluenesulfonamide 19 was examined by 1H NMR (Appendix 20),

with mesitylene (0.1 mmol) as internal standard. The results are summarized in Table 3.5.

In all cases, the conversion of THF was achieved in yields from 32% to 99%. 1Fe gave the

best result (99% yield), comparable to that of amination of THF in ionic liquid using the

*,Br 28 analogous Cu(I) catalyst [Tpm Cu(NCMe)](BF 4) reported by Pérez and co-workers.

As indicated in Table 3.5, the anionic scorpionate ligand coordinated Fe(II) complexes

3Fe and 4Fe (Table 5, entries 9, 13) were found to be less active toward amination of THF

than those of neutral scorpionate ligand coordinated Fe(II) analogues 1Fe and 2Fe (Table

3.5, entries 2, 6). This is presumably due to 3Fe and 4Fe featuring electron rich anionic

scorpionate ligands, which reduces reactivity.4 The electrophilic amination using

Fe Fe [Fe(NCMe) 6](BF 4)2 was found to be more efficient than 3 and 4 (Table 3.5, entry 17),

which also supports the hypothesis described above. Not surprisingly, the use of

scorpionate ligands bearing phenyl groups on 3-pyrazolyl positions gave the amination

product in lower yield than the use of scorpionate ligands bearing methyl groups (Table

122

3.5, entry 2 vs 6; entry 9 vs 13). This is presumably due to the same hypothesis depicted

for the analogous aziridination reaction in which intramolecular amination of the phenyl

group on the scorpionate ligand reduces the catalytic activity of the catalyst. The

analogous Mn(II) catalysts were found to be the least reactive catalysts which gave yields

of amination product 19 lower than 40% (Table 3.5, entries 1, 5, 12, 16). As summarized in Table 3.5, the Mn(II), Co(II) and Ni(II) salts all show comparable or better reactivity than the analogous scorpionate ligand complexes. The catalytic ability of these metal catalysts for C-H amination reactions is also clearly reflected by the necessary reaction times. Reasonable conversion of THF 18 to 19 (71% yield) was still achieved when only

5 equivalents of THF relative to PhI=NTs was applied, with 1Fe as catalyst (Table 3.5, entry 20).

In order to probe the rate-determining step of the C-H bond amination reaction of

Fe THF catalyzed by 1 , a competition experiment employing a 1:1 ratio of THF to THF-d8

Fe provided a kinetic isotope effect, kH/kD, of 1.4 for 1 (Figure 3.4). The KIE value is much smaller than the classical KIE value for hydrogen atom transfer (6.5) 26 and is thus

indicates that C-H bond cleavage step is not the rate-determining step in the amination

reaction of THF.

123

Table 3.5. Complexes 1M-4M catalyzed amination of THF with PhI=NTs.

Entry Catalyst Reaction time a Yield (%) b

Me,Me 1 [Tpm Mn(CH 3CN) 3](BF 4)2 60 min 32

Me,Me 2 [Tpm Fe(CH 3CN) 3] (BF 4)2 30 min 99

Me,Me 3 [Tpm Co(CH 3CN) 3] (BF 4)2 30 min 69

Me,Me 4 [Tpm Ni(CH 3CN) 3] (BF 4)2 30 min 74

Ph 5 [Tpm Mn(CH 3CN) 3] (BF 4)2 60 min 33

Ph 6 [Tpm Fe(CH 3CN) 3] (BF 4)2 30 min 68

Ph 7 [Tpm Co(CH 3CN) 3] (BF 4)2 30 min 60

Ph 8 [Tpm Ni(CH 3CN) 3] (BF 4)2 30min 65

Me,Me 9 [Tp Fe(CH 3CN) 3] BF 4 30 min 67

Me,Me 10 [Tp Co(CH 3CN) 3] BF 4 30 min 64

Me,Me 11 [Tp Ni(CH 3CN) 3] BF 4 50 min 66

Ph,Me 12 [Tp Mn(CH 3CN) 3] BF 4 60 min 38

124

Ph,Me 13 [Tp Fe(CH 3CN) 3] BF 4 30 min 36

Ph,Me 14 [Tp Co(CH 3CN) 3] BF 4 30 min 29

Ph,Me 15 [Tp Ni(CH 3CN) 3] BF 4 40 min 60

16 [Mn(CH 3CN) 6] (BF 4)2 30 min 34

17 [Fe(CH 3CN) 6] (BF 4)2 30 min 82

18 [Co(CH 3CN) 6] (BF 4)2 30 min 63

19 [Ni(CH 3CN) 6] (BF 4)2 30 min 79

c Me,Me 20 [Tpm Fe(CH 3CN) 3] (BF 4)2 30 min 71

With 2 mL THF and 0.2 mmol PhINTs. a Complete dissolution of PhINTs varies. b 1H NMR yield (with mesitylene as internal standard) based on the amount of PhINTs. C with THF to PhINTs in 5:1 ratio.

125

7.83 7.81 7.32 7.29 5.66 5.64 5.63 5.33 5.12 3.72 3.70 3.68 2.44 2.13 1.92 1.89 1.87 1.84 1.83 1.81 1.80 1.79 1.77 3.77 4.06 1.45 1.01 0.55 2.00 5.93 1.13 3.21

8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 δ (ppm) 1 Figure 3.4. H NMR spectrum (CDCl 3, 295 K): C-H bond amination prodcuts of Fe competition reaction of THF and THF-d8 catalyzed by 1 with PhI=NTs.

126

Having successfully achieved the C-H bond amination of THF which contains

Fe weak C-H bond, we then decided to use 1 as catalyst to examine the C-H bond

amination of less reactive hydrocarbon substrates containing strong C-H bonds. Cyclic

alkane substrates cyclohexane 20 and cyclopentane 21 were first introduced in such amination reactions. As depicted in Table 3.6, the C-H bond amination of cyclohexane 20

Fe and cyclopentane 21 mediated by 5 mol% 1 in CH 2Cl 2 were found to give the corresponding products ( 22 , 23 ; Appendix 18, 19) in low isolated yields (40% and 30%, respectively) after 5 hours. The conversion yields are much lower than the analogous amination of tetrahydrofuran with 1Fe (Table 3.5, entry 2). And the amination yield of

cyclohexane 20 is also lower than that achieved by using of [Tp Br 3Cu(NCMe)] as catalyst reported by Pérez and co-workers. 27 The differences in activity shown between

cyclohexane or cylcopentane and tetrahydrofuran might be due to their C-H bond

dissociation energies, since cyclohexane and cyclopentane have higher bond dissociation

energies than that of tetrahydrofuran. 4

Me,Me Fe Table 3.6. [Tpm Fe(CH 3CN) 3] (BF 4)2 (1 ) catalyzed amination of cyclic alkane substrates with PhI=NTs. Entry substrate a Reaction time amines Yield (%) b

1 30 min 45

2 30 min 60 a b 2 mL Substrate and 0.2 mmol PhINTs, and 4 mL CH 2Cl 2 as solvent, at R.T. Isolated yield.

127

C-H bond Amination of Aromatic Substrates

Following the preliminary investigation of inert cyclic alkane substrates, we then

expanded the substrate scope to aromatic hydrocarbons. In our initial investigation of C-

H amination of aromatic hydrocarbons, we employed PhI=NTs (0.2 mmol) as the nitrene

source and benzene 24 (2 mL) as substrate. After the reaction was run in CH 2Cl 2 at room

temperature with 5 mol% of 1Fe and 4 Å molecular sieves for 30 min (with complete

dissolution of PhI=NTs observed within 5 min), benzene 24 was converted into N-

tosylaminobenzene 32 in 45% isolated yield (Table 3.7, entry 1; Appendix 10).

Introducing a nitrogen functional group into benzene is currently achieved by indirect

methods which require the pre-installation of functional groups such as nitro, chloro or

hydroxyl substituents, while examples of the direct amination of benzene are sparse. 27

This is presumably due to the relatively high bond dissociation energy of the benzene C-

H bonds. 4 With regard to the use of nitrene insertion methodologies, Ayyangar and co- workers reported a noncatalytic method which the reaction of tosylazide with benzene at

160 oC gave a very low yield of nitrene insertion product, 34 while Pérez and co-workers

reported the conversion of benzene into N-tosylaminobenzene 32 using catalytic amount of Cu(I) catalyst [Tp Br 3Cu(NCMe)] in 40% yield at room temperature. 27,35

Encouraged by the exceptional catalytic reactivity of 1Fe towards the amination of aromatic C-H bonds in benzene, we then examined the catalytic reactivity and chemoselectivity with substrates containing both aromatic and benzylic C-H bonds. Thus, aromatic substrates 25-31 bearing one, two or three alkyl substituents were examined using reaction conditions similar to those used for benzene. To our surprise, the reaction

128

of PhI=NTs with mesitylene 31 in CH 2Cl 2 gave the aromatic C-H bond insertion product

45 in 81% yield at room temperature, with only a trace amount of the benzylic amination

product (Table 3.7, entry 8; Appendix 11). This behavior was not limited to mesitylene

31 , since other mono- or dimethyl substituted benzene substrates were also found to

show excellent chemoselectivities toward aromatic C-H bonds in moderate to good

reaction yields (Table 3.7, entry 2, 5, 6, 7). The use of toluene 25 as substrate led to the

formation of a mixture of two products, the para and ortho derivatives ( 33 , 34 ; 1.4:1

ratio, 60% overall yield; Appendix 17), as the result of the nitrene insertion into the para and ortho C-H bonds of the benzene ring (Table 3.7, entry 2). Again, only a trace amount of the benzylic C-H bond amination product was observed. Not surprisingly, the reactions of PhI=NTs with o-xylene 29 or m-xylene 30 also gave the expected mixture of products derived from the activation of aromatic C-H bonds (Table 3.7, entry 6, 7; Appendix 13,

14). The use of p-xylene 28 led to the formation of both aromatic and benzylic C-N bond formation products 39 and 40 in 6.2:1 ratio (Table 3.7, entry 5; Appendix 12), which is

presumably due to the fact that the benzylic C-H bonds of p-xylene 28 are activated by para methyl substituents, thus a considerable amount of product 40 was obtained.

However, when ethylbenzene 26 or isopropyl-benzene 27 containing secondary or

tertiary C-H bonds were used as the substrate, high percentages of benzylic C-H bond

nitrene insertion products 36 and 38 were observed (Table 3.7, entry 3, 4 Appendix 16,

17). As indicated in entry 3 and 4 in Table 3.7, nearly equal amounts of benzylic and aromatic C-H insertion products were obtained.

129

He and co-worker reported a similar transformation of mesitylene using AuCl 3 as

catalyst in which the nitrene fragment was exclusively inserted into aromatic C-H

bonds. 15 However, when tertiary benzylic C-H sites are available, both aromatic and benzylic tertiary C-H bond were functionalized. When less substituted benzenes or benzene itself were studied as substrates, less than 5% yield of products derived from the insertion of the nitrene fragment into the aromatic C-H bonds was obtained. 15 As mentioned above, the direct amination of benzene has been achieved by nitrene insertion with [Tp Br 3Cu(NCMe)], as reported by Pérez and co-workers. 27,35 However, they found

that when benzylic C-H bonds were available, such as in toluene and mesitylene, the C-H

bond amination ractions exclusive took place at the alkyl substitutents sites, with no

functionalization of aromatic C-H bonds.

Me,Me Fe Therefore, [Tpm Fe(NCMe) 3](BF 4)2 (1 ) shows unique reactivity and chemoselectivity toward aromatic C-H bonds over primary benzylic C-H bonds, and it also induces the functionalization of weak benzylic C-H sites as for p-xylene,

ethylbenzene or isopropylbenzene, along with the functionalization of aromatic C-H sites.

130

Table 3.7. Intermolecular C-H bond amination reaction of aromatic substrates mediated Me,Me Fe by [Tpm Fe(NCMe) 3](BF 4)2 (1 ) with PhI=NTs. Entry substrate a Reaction time c amines Yield (%)b

1 30 min 45

CH 3 Ts N 2 30 min H , 60 33 1:1.4

3 30 min , 62 1.1 : 1

CH3 4 H H 30 min , 57 CH3 H 27 1.1 : 1 CH 3 Ts N H 5 30 min , 66 39 CH3 6.1: 1

6 30 min , 63

4: 1

CH Ts 3 N 7 30 min , H 74

H3C 4.9: 1 44

H H CH CH 2 2 Ts H N 8 30 min H 81

H3C CH3 H3C CH3 31 45 a 1 mL substrate or 2 mL substrate (for benzene and toluene substrates) and 0.2 mmol PhINTs, 4 b c mL CH 2Cl 2 as solvent, at R.T.. Isolated yield. Complete dissolution of PhINTs in 5 min.

131

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134

CHAPTER 4: MASKED LEWIS ACID [Fe(NCMe)6](BF 4)2 CATALYZED

CYCLOADDITION REACTIONS

Nitrogen-containing heterocycles are commonly found in biologically active

compounds, natural products and pharmaceuticals, 1-3 which play important roles in

modern medicinal and synthetic chemistry due to their specific biological behaviors and

remarkable structural diversities. Therefore, the search for innovative approaches toward

the synthesis of heterocyclic compounds is of great importance, as strained three-

membered rings aziridines are versatile building blocks due to their facial ring opening

reactions with nuclophiles. 4-6 These reactions have led to the formation of various

nitrogen-containing compounds. Among these, Lewis acid promoted formal [3+2]

cycloaddition reactions of aziridines to dipolarophiles have shown increasing promise

toward the formation of five-membered nitrogen-containing heterocycles, since such

heterocycles can be created in one step with high efficiency, chemoselectivity and atom

economy. 7 Intense efforts have been contributed to the advancement of [3+2] cycloaddition reactions involving azomethine ylides generated from the C-C bond cleavage of aziridines. 8,9 In contrast, the analogous transformations of aziridines to five-

membered nitrogen-containing heterocycles through C-N bond cleavage of aziridines are

less well explored. Mann and co-workers recently reported a uncommon zwitterionic 1,3-

dipole generated from 2-phenyl-N-tosylaziridine via C-N bond cleavage induced by the

10 addition of a stoichiometric amount of the Lewis acid BF 3·Et 2O. Since then, Lewis acid promoted formal [3+2] cycloaddition reactions of aziridines via C-N bond cleavage with alkenes, 11 alkynes, 12,13 aldehydes/ketones or organic nitriles, 14-17 leading to the formation

135

of five-membered nitrogen-containing heterocycles, have been explored. Although this

reaction pattern frequently emerges in current reports, catalytic examples for the

synthesis of five-membered nitrogen-containing heterocycles are rare. Mann and co-

workers reported the formation of pyrrolidine derivatives achieved by the cycloaddition

of 2-phenyl-N-tosylaziridine to alkenes using a stoichiometic amount of the Lewis acid

10 BF 3·Et 2O. The analogous transformation of aziridines to substituted pyrrolidines was

also induced by addition of catalytic amount of Sc(OTf) 3 as reported by Yadav and co- workers. 11 Formation of oxazoline derivatives through cycloadditions of aziridines to

carbonyl compounds using a stiochiometric amount of Cu(OTf) 2 or catalytic quantity of

16 14 Sc(OTf) 3 was reported by the Ghorai and Nguyen groups, respectively. More recently,

FeCl 3 and AgSbF 6 have been shown to act as efficient catalysts in the cycloaddition reactions of aziridines with alkynes. 12,13 However, many transformations of aziridines require the presence of a stoichiometric amount of the Lewis acid (BF 3·Et 2O, Cu{OTf} 2)

or heavy and rare metal catalysts (Sc{OTf} 3, AgSbF 6) to achieve the cycloaddition

products in good yields. On the other hand, iron is one of the most abundant metals on

earth and consequently is one of the most economical and environmentally friendly

metals. Despite its advantages, iron catalysts remain surprisingly relatively

underdeveloped compared to other transition metals.18 As just mentioned, Wang and co- workers reported the formation of 2-pyrrolines via [3+2] cycloaddition of azridines with arylalkynes catalyzed by FeCl 3. However, no reactions were reported for aziridines and other substrates such as alkenes. 12

136

In the present chapter, we describe the in situ formation of a pyrrolidine derivative generated from the reaction of styrene and PhI=NTs in CH 2Cl 2, a [2+1+2] cycloaddition

process induced by the presence of a catalytic amount of masked Lewis acid

[Fe(NCMe) 6](BF 4)2. We propose that a zwitterionic 1,3-dipole intermediate is produced

in this process via the C-N bond cleavage of 2-phenyl-N-tosylaziridine as reported by

Mann and co-workers. 10 Inspired by the in situ formation of pyrrolidine derivatives with

styrene, we extend our reaction substrates to a variety of alkenes, aldehydes, ketones and

alkynes. We present various transformations of 2-phenyl-N-tosylaziridine to five- membered nitrogen-containing heterocycles such as pyrrolidines, oxazolidines and 2- pyrrolines in the presence of a catalytic amount of [Fe(NCMe) 6](BF 4)2.

The aziridination of styrene with PhI=NTs catalyzed by [Fe(NCMe) 6](BF 4)2 gave

71% isolated yield of aziridine product 2 in CH 3CN as solvent (Table 3.1, entry 17),

while under the same reaction conditions, no aziridine was obtained in CH 2Cl 2 (Table 3.1, entry 16). In fact, when a mixture of styrene (1.0 mmol), PhI=NTs (0.2 mmol) and

[Fe(NCMe) 6](BF 4)2 (5 mol%) in CH 2Cl 2 was stirred for 30 min at room temperature, we

noticed the formation of two diastereomeric products. After purification by column

chromatography on silica gel, the 1H and 13 C NMR spectra of the inseparable diastereomers were consistent with 2,4-diphenyl-1-tosyl-pyrrolidine 3 as cis and trans isomers in a ratio of nearly 1:1 (Appendix 21).19 Based on the literature precedent, we conclude that [Fe(NCMe) 6](BF 4)2 initially catalyzes the aziridination reaction of styrene with PhI=NTs to form 2-phenyl-N-tosylaziridine 2, and then 2 further reacts in situ with styrene to give rise to a pyrrolidine derivative 3 through a formal [3+2] cycloaddition

137

10,11,20 reaction induced by [Fe(NCMe) 6](BF 4)2 in CH 2Cl 2 (Scheme 4.1). We propose that

formation of a zwitterionic 1,3-dipole intermediate 2a is induced by [Fe(NCMe) 6](BF 4)2 in CH 2Cl 2, then the olefinic π system of styrene attacks at the benzylic position of the 1,3-

dipole intermediate 2a , giving rise to a stable benzylic carbocation 3a, which is then

attacked by the adjacent amide nucleophilie to form the pyrrolidine derivative 3 (Scheme

4.1). Significantly, this reaction provided pyrrolidine 3 as the only detectable regioisomer, with no observation of pyrrolidine 4, presumably owing to the poor stability and sterics of intermediate 4a. The use of different solvents was shown to lead to the formation of different products; therefore, the formation of substituted pyrrolidine 3 suggested that [Fe(NCMe) 6](BF 4)2 may behave as an unmasked Lewis acid in CH 2Cl 2.

When CH 3CN is used as the reaction medium, the Fe(II) center is protected by the coordinated CH 3CN molecules and loses its Lewis acidity. Therefore, the aziridine product 2 is obtained, with no observation of [3+2] cycloaddition product 3. The conversion of olefins into aziridines in CH 3CN at 85 ºC using Fe(OTf) 2 as catalyst and

PhI=NTs as nitrene source was reported by Bolm and co-workers. Without adding ligand,

only 23% yield of 2-phenyl-N-tosylaziridine 2 was obtained with styrene as substrate; however, the formation of pyrrolidine derivatives was not observed. 21 Therefore,

[Fe(NCMe) 6](BF 4)2 is unmasked as a Lewis acid, and to the best of our knowledge, our

reaction system is the first example of catalysis inducing the formation of pyrrolidine

derivatives arising from the reaction of simple alkenes with PhI=NTs as nitrene source.

138

Scheme 4.1. [2+1+2] cycloaddition reaction of styrene with PhI=NTs in CH 2Cl 2 catalyzed by [Fe(NCMe) 6](BF 4)2

139

[2+1+2] Cycloaddition of Alkenes with PhI=NTs

We initially investigated the scope and the generality of the in situ formation of

substituted pyrrolidines. The reactions were conducted in CH 2Cl 2 at room temperature in the presence of 5 mol% of [Fe(NCMe) 6](BF 4)2 (Scheme 4.2). A variety of para -

substituted styrenes (0.5 mmol) bearing electron-donating and electron-withdrawing

groups were employed as the reaction substrates and PhI=NTs (0.2 mmol) was

introduced as the nitrene source. As indicated in Table 4.1, when the para substituent is

H-, methyl- or chloro-, a cis and trans mixture of substituted pyrrolidine isomers was obtained in a ratio of nearly 1:1, which were inseparable on TLC (Table 4.1, entries 1-3).

The presence of an electron-donating methyl substituent on the para position of styrene

46 was shown to favor the cycloaddition reaction, with the reaction finished in 30 min, and the corresponding pyrrolidine product 50 obtained in 70% yield (Appendix 22). In contrast, the chloro substituent on the para position of styrene 47 appeared to retard the reaction, with the product 51 obtained in 69% yield only after 2.5 hours (Appendix 23).

The para -substituted styrenes bearing strong electron-withdrawing groups such as NO 2-

49 and CF 3- 48 gave the corresponding aziridination products 53 and 52 in moderate

yields, but no pyrrolidine derivatives were observed (Table 4.1, entries 4, 5; Appendices

2, 3). Therefore, the para substituents have significant effects on the formation of

pyrrolidine derivatives from styrenes. As indicated in Scheme 4.2, when para -substituted

styrene 1′ was used as substrate towards the [2+1+2] cycloaddition reaction with nitrene

precursor PhI=NTs, a [2+1] aziridination reaction occurred initially to generate a 2-

phenyl-N-tosylaziridine derivative 2′ in situ , in the presence of [Fe(NCMe) 6](BF 4)2 as

140

catalyst. Then 2′ was activated by [Fe(NCMe) 6](BF 4)2 in the non-coordinating solvent

CH 2Cl 2 to form a zwitterionic 1,3-dipole intermediate 2a ′ via C-N bond cleavage, which was then attacked by the olefinic π system of para -substituted styrene at the benzylic position of 2a′, giving rise to benzylic cation 3a ′. At last, intramolecular ring closure of

3a ′ with the adjacent amide gives the substituted pyrrolidine product 3′. Overall, this reaction process constitutes a [2+1+2] cycloaddition reaction to generate pyrrolidine derivatives. As indicated in Scheme 4.2, the two charges of the zwitterionic 1,3-dipole intermediate 2a ′ are stabilized in an exo by both the tosyl and phenyl groups. Thus, an

electron-donating substituent on the para position of the phenyl ring stabilizes the zwitterionic intermediate, while this intermediate is destabilized by an electron- withdrawing substituent on the para position of the phenyl ring. Therefore, para - substituted styrene substrates with electron-donating groups lead to the formation of the desired pyrrolidine products, while the analogous para -substituted styrene substrates bearing electron-withdrawing groups disfavored the desired [2+1+2] cycloaddition reactions, and only the [2+1] aziridination reactions were achieved (Table 4.1, entries 4-

5).

Under similar reaction conditions, other alkenes were also introduced as substrates to examine the formation of pyrrolidine derivatives (Table 4.1, entries 6-7).

Unfortunately, both trans -stilbene 10 and cyclohexene 7 showed no reactivity towards formation of pyrrolidine derivatives. The reactions of trans -stilbene 10 and cyclohexene

7 with PhI=NTs catalyzed by [Fe(NCMe) 6](BF 4)2 in CH 2Cl 2 showed similar results as

Me,Me Fe those described in the previous chapter using [Tpm (NCMe) 3](BF 4)2 (1 ) as catalyst.

141

The reaction of trans -stilbene 10 with PhI=NTs gave the olefinic C-H bond amination

product 16 in 40% yield (Appendix 6). The formation of 2,3,4,5-tetraphenyl-pyrrolidine

from trans -stilbene is presumably disfavored by the steric hindrance. Both aziridination

product 12 and C-H bond amination product 13 were obtained in 17% overall yield with

cyclohexene 7 as substrate (Appendices 7, 8). This result shows that the formation of a

zwitterionic 1,3-dipole intermediate from a nonactivated alkene (as for cyclohexene) is

not favorable.

The results described above demonstrate that the formation of pyrrolidine

derivatives via [2+1+2] cycloaddition reactions of alkenes and PhI=NTs catalyzed by

unmasked Lewis acid [Fe(NCMe) 6](BF 4)2 in CH 2Cl 2, is controlled by the electronic nature and steric effect of the alkene substrates.

142

Table 4.1. [2+1+2] cycloaddition of olefins with PhI=NTs in the presence of unmasked

Lewis acid [Fe(NCMe) 6](BF 4)2 in CH 2Cl 2. Entry substrate a Reaction time c product Yield (%) b

1 30 min 55 (d.r. 1:1.1)

2 30 min 70 (d.r. 1:1.2) H C 3 46

3 2.5 h 69 (d.r. 1:1)

4 5 h 65 F C 3 48

5 5 h 64

6 3 h 40 10

NHTs

7 80 min NTs , 17 12 13 a b 1.0 mmol substrate and 0.2 mmol PhINTs, with 3 mL CH 2Cl 2 as solvent, at R.T. Isolated yield. c Complete dissolution of PhINTs in 5 min.

143

Ts 1' N PhI=NTs R N Fe(CH CN) (BF ) R 3 6 4 2 Fe(CH3CN)6(BF4)2 CH Cl Ts 1' 2 2 R CH2Cl2 2' R 3'

R = Me, H, Cl, CF3, NO2 C-N breaking

R R

Ts N 1' R N Ts 2a' 3a' R

Scheme 4.2. [2+1+2] cycloaddition reaction of para -substituted styrene with PhI=NTs in

CH 2Cl 2 mediated by unmasked Lewis acid [Fe(NCMe) 6](BF 4)2.

144

[3+2] Cycloadditon of Aziridine with Alkenes, Aldehydes, Ketones and Alkynes

The cycloaddition reaction of aziridines with dipolarophiles represents an

innovative approach to the formation of heterocycles such as pyrrolidine, 10,11 pyrroline, 12,13 oxazolidine 15 and imidaolines.15-17 Encouraged by the catalytic reactivity of the unmasked Lewis acid [Fe(NCMe) 6](BF 4)2 in [2+1+2] cycloaddition of alkenes with

PhI=NTs, we examined its catalytic reactivity in the formal [3+2] cycloaddition reaction of pre-formed 2-phenyl-N-tosylaziridine with various dipolarophiles, including arylalkenes, aldehydes, ketones, alkynes and nitriles (Scheme 4.3). Table 4.2 outlines the scope of [Fe(NCMe) 6](BF 4)2 catalyzed condensation reactions of 2-phenyl-N-

tosylaziridine 2 to various dipolarophile substrates in CH 2Cl 2 at room temperature. Under

optimized reaction conditions, a wide variety of nitrogen-containing heterocycles was

obtained with high regioselectivity and moderate to good isolated yields.

Cycloadditions of 2-phenyl-N-tosylaziridine 2 with p-methylstyrene 46 and p-

chlorostyrene 47 in CH 2Cl 2 at room temperature were shown to produce substituted pyrrolidines 60 (Appendix 24) and 61 in a cis/tran s ratio of approximately 1:1, in 80% and 67% yields, respectively (Table 4.2, entries 1-2). Unlike the in situ formation of pyrrolidine derivatives via cycloaddition of para -substituted styrenes and PhI=NTs, which were carried out with low catalyst loading (5 mol%, Table 4.1, entries 1-3), the reactions of 2-phenyl-N-tosylaziridine 2 with p-methylstyrene 46 and p-chlorostyrene 47 require higher catalyst loading (10 mol%) in order to obtain high conversions and yields.

145

Scheme 4.3. Formal [3+2] cycloaddition of aziridine 2 with various dipolarophiles mediated by [Fe(NCMe) 6](BF 4)2.

Scheme 4.4. Hydrolysis of 1,3-oxazolidine derivative 64 to 1,2-amino alcohol 69 .

146

The complete conversion of 2-phenyl-N-tosylaziridine into 1,3-oxazolidines was achieved with aldehyde or ketone substrates using 20 mol% of [Fe(NCMe) 6](BF 4)2.

Interestingly, the diastereoselectivity of the 1,3-oxazolidine products largely depends on

the reaction time and the amount of catalyst. When reaction of 2-phenyl-N-tosylaziridine

2 (0.2 mmol) with benzaldehyde 54 (0.5 mmol) was conducted in CH 2Cl 2 at room

temperature using 10 mol% [Fe(NCMe) 6](BF 4)2 as catalyst, the diastereomeric ratio of 62

was 5.7:1 ( cis:trans ) with 90% conversion of 2-phenyl-N-tosylaziridine 2 after 60 min.

However, when the reaction was carried out with 20 mol% [Fe(NCMe) 6](BF 4)2, the 2- phenyl-N-tosylaziridine 2 was all consumed after 2 hours and a cis and trans mixture of

1,3-oxazolidine 62 in a 1:1.2 ratio were obtained (Table 4.2, entry 3; Appendix 25). This observation is presumably due to isomerization of the kinetically formed cis isomer to the trans isomer via C-O bond cleavage of 1,3-oxazolidine induced by [Fe(NCMe) 6](BF 4)2.

This cis to trans isomerization process of 1,3-oxazolidines has also been observed by the

Nguyen 14 and Ghorai groups 16 , respectively. Meanwhile, reactions of 2-phenyl-N- tosylaziridine 2 with 4-methylbenzaldehyde 55 and acetophenone 56 also gave the desired 1,3-oxazolidine derivatives 63 and 64 , respectively, in the presence of 20 mol% of [Fe(NCMe) 6](BF 4)2 (Table 4.2, entries 4-5; Appendices 26-27). Interestingly, when the isolated 1,3-oxazolidine derivative 64 was kept in an NMR tube in CDCl 3 for about 30

days, hydrolysis of 64 to the corresponding 1,2-amino alcohol 69 (Appendix 28) was

observed (Scheme 4.4). 16

The formal [3+2] cycloaddition of 2-phenyl-N-tosylaziridine was also examined

with alkynes as dipolarophiles using 20 mol% of [Fe(NCMe) 6](BF 4)2 (Table 4.2, entries

147

6-7). Reactions were conducted in CH 2Cl 2 at room temperature with an alkyne to 2- phenyl-N-tosylaziridine mole ratio of 3:1. In order to achieve high conversion of 2-

phenyl-N-tosylaziridine, longer reaction times were required for the reactions with alkynes, compared with the reactions with alkenes, aldehydes and ketones as dipolarophiles. The reaction of 2-phenyl-N-tosylaziridine 2 with 1-phenyl-1-propyne 58 afforded substituted 2-pyrroline 67 as the only regioisomer in 68% isolated yield after 4 hours (Table 4.2, entry 7; Appendix 30). A 1.4:1 mixture of two regioisomeric 2- pyrroline derivatives 65 and 66 was obtained from the reaction of 2-phenyl-N- tosylaziridine 2 with phenylacetylene 57 after 4 hours (Table 4.2, entry 6; Appendix 29).

Analysis of the NMR spectrum of the major product 65 was consistent with 2,4-diphenyl-

2-pyrroline reported by Wender and co-workers. 13 The structure of the minor product was

assigned to 2,5-diphenyl-2-pyrroline 66 based on a COSY experiment; the J-coupling excludes the formation of 70 and 71 (Scheme 4.5). Our proposed mechanism for the observation of two regioisomeric products of the reaction of 2 and 58 is shown in Scheme

4.5. As indicated in Scheme 4.5, two C-N bonds of 2-phenyl-N-tosylaziridine 2 are theoretically in competition. Thus, it is proposed that the reaction involves two possible zwitterionic 1,3-dipole intermediates 2a and 2b . 2a and 2b are attacked by phenylacetylene 58 , generating two stable benzylic like carbocations 65a and 66a , respectively, which then undergo intramolecular cyclizations, giving rise to the desired 2- pyrroline derivatives 65 and 66. As expected, the more stable zwitterionic 1,3-dipole intermediate led to the formation of 65 as the major product.

148

As expected, the formal [3+2] cycloaddition of 2-phenyl-N-tosylaziridine 2 with acetonitrile 59 using masked Lewis acid [Fe(NCMe) 6](BF 4)2 as catalyst did not form the

desired substituted imidazoline product 68 (Table 4.2, entry 8). This is presumably due to

the coordination of nitrile to the iron(II) center, thus disabling its catalytic reactivity.

In conclusion, we have discovered that unmasking of the Lewis acid

[Fe(NCMe) 6](BF 4)2 effects the construction of substituted pyrrolidines from the reaction

of arylalkenes with nitrene precursor PhI=NTs. This iron(II) catalyst has also been

employed to induce the formal [3+2] cycloaddition of 2-phenyl-N-tosylaziridine with various dipolarophiles such as alkenes, carbonyls and alkynes, for the synthesis of five- membered nitrogen-containing heterocycles; excellent yields and regioselectivity has been achieved in these cycloaddition reactions.

149

Table 4.2. [3+2] cycloaddition of 2-phenyl-N-tosylaziridine with various dipolarophiles in the presence of unmasked Lewis acid [Fe(NCMe) 6](BF 4)2 in CH 2Cl 2. Entry substrate a mol.% cat. Reaction time product Yield (%) b

1 10 40 min 80

2 10 2 h 67 c

3 20 2 h 87

4 20 2 h 90

5 20 2 h 79

6 20 4 h 64 NTs 65 1.4:1

N Ts 66

CH3 7 20 4 h 68 58

8 20 4 h ~0

a b 0.5 mmol substrate and 0.2 mmol aziridine, and 3 mL CH 2Cl 2 as solvent, at R.T. Isolated yield. c 70% conversion of aziridine.

150

H N Ts N Ts H 65 70 not observed

more stable

Ts 58 2a Ts Ts N N N H Ts N H H Fe(CH3CN)6(BF4)2 70a H CH2Cl2 65a 2 unstable cation C-N breaking unfavorable stable cation favorable

less stable

Ts 58 2b N Ts Ts H N 71a N Ts N H Fe(CH CN) (BF ) 3 6 4 2 H 2 CH2Cl2 H C-N breaking 66a unstable cation unfavorable stable cation favorable

H N Ts N Ts H 66 71 not observed

Scheme 4.5. Proposed mechanism showing the formation of 2-pyrroline derivatives from the cycloaddition of aziridine 2 and phenylacetylene 57 with [Fe(NCMe) 6](BF 4)2.

151

Experimental Procedures for Chapter 3 and Chapter 4

General methods: All materials purchased from commercial suppliers were ACS

reagent-grade or better and used without further purification unless noted. Liquid organic

substrates were ACS reagent-grade or better and purified by either vacuum distillation

over calcium hydride or drying over 4 Å molecular sieves, and followed by the freeze-

pump-thaw method prior to use. Dichloromethane and acetonitrile were degassed and

distilled over CaH 2 before use. All reactions were performed in oven-dried glassware under an Argon atmosphere. Organic solutions were concentrated under reduced pressure by rotary evaporation. Thin layer chromatography plates were visualized by ultraviolet light. Flash chromatography was carried out by using forced-flow method on 32–63D

60Å silica gel. 1H, 13 C NMR and 2D NMR (COSY) spectra were recorded with a Bruker

Avance 300 MHz NMR spectrometer and were referenced internally according to the

TMS resonance.

Preparation of N-tosyliminophenyliodinane (PhI=NTs): PhI=NTs was prepared

based on a literature procedure. 22 Iodosobenzene diacetate (9.60 g, 30 mmol) was gradually added to a methanol solution (120 ml) of p-toluene-sulfonamide (5.12 g, 30 mmol), potassium hydroxide (KOH) (4.20 g, 75 mmol) below 10 ºC with stirring. The

resulting yellow homogeneous solution was stirred for three hours at room temperature.

After the reaction, the mixture was poured into distilled water to precipitate a yellow

colored solid on standing overnight, which was recrystallized from hot methanol to give

PhI=NTs in 5.6 g (yield: 50%).

152

Typical procedure for aziridination: To a stirred solution of alkene (1.0 mmol)

and metal catalyst in anhydrous CH 2Cl 2 (3 mL) was added solid PhI=NTs (0.2 mmol) in

one portion at room temperature under argon. The reaction mixture was then allowed to

stir for a certain time based on the dissolution of solid PhI=NTs. Upon completion the

reaction mixture was filtered through a plug of silica gel eluting with ethyl acetate and

the filtrate was concentrated under vacuum. Then the residue was applied to column

chromatography to afford the purified product.

Competition experiment for Hammett plot: To a stirred solution of styrene (0.2

Me,Me Fe mmol), para -substituted styrene (0.2 mmol) and [Tpm M(CH 3CN) 3](BF 4)2 1 (5

mol%) in anhydrous CH 3CN (3 mL) was added solid PhI=NTs (0.2 mmol) in one portion at room temperature under argon. The reaction mixture was then stirred for 30 min at room temperature. Upon completion the reaction mixture was filtered through a plug of silica gel eluting with ethyl acetate and the filtrate was concentrated under vacuum. The yields of aziridines were then analyzed by 1H NMR with mesitylene (0.1 mmol) as internal standard to determine the amount of unreacted styrene and para -substituted styrene.

Calculations: kY/kH = log(Y f/Y i) / log(H f/H i)

Yf and Y i: the final and initial quantities of para -substituted styrene.

Hf and H i: the final and initial quantities of styrene.

Typical procedure for C-H bond amination reactions: To a stirred solution of

Me,Me Fe organic substrate and [Tpm M(CH 3CN) 3](BF 4)2 1 (5 mol%) in anhydrous CH 2Cl 2

153

(4 mL) with 4 Å molecular sieves was added solid PhI=NTs (0.2 mmol) in one portion at

room temperature under argon. The solid PhI=NTs was completely dissolved in less than

5 min. Then the reaction mixture was stirred for 30 min at room temperature. Upon

completion the reaction mixture was filtered through a plug of silica gel eluting with

ethyl acetate and the filtrate was concentrated under vacuum. Then the residue was

applied to column chromatography to afford the purified product. The THF C-H bond

amination product tosylamino tetrahydrofuran 19 was not further purified by column

chromatography, the crude product was analyzed by 1H NMR with mesitylene (0.1 mmol) as internal standard to determine the yield of 19 .

General procedure of [Fe(CH 3CN) 6](BF 4)2 mediated [2+1+2] cycloaddition of

nitrene to alkenes: To a stirred solution of alkene (1.0 mmol) and [Fe(CH 3CN) 6](BF 4)2 (5 mol%) in anhydrous CH 2Cl 2 (3 mL) was added solid PhI=NTs (0.2 mmol) in one portion

at room temperature under argon. The reaction mixture was then allowed to stir for 30

min – 5h based on the alkene substrates used. Upon completion the reaction mixture was

the filtered through a plug of silica gel eluting with ethyl acetate and filtrate was

concentrated under vacuum. Then the residue was applied to column chromatography to

afford the purified product.

General procedure of [Fe(CH 3CN) 6](BF 4)2 mediated [3+2] cycloaddition of 2-

phenyl-N-tosylaziridine to dipolarophiles: Iron(II) salt Fe[(CH 3CN) 6](BF 4)2 (10-20 mol%) was added into CH 2Cl 2 solution (3 mL) with 2-phenyl-N-tosylaziridine 2 (54.7 mg, 0.2 mmol) and dipolarophile (0.5 mmol alkene, aldehyde, ketone, alkyne or acetonitrile) under argon. The reaction mixture was then stirred at room temperature.

154

Upon complete formation of the aziridine 2 (determined by 1H NMR), the reaction

mixture was filtered through a plug of silica gel eluting with ethyl acetate and the filtrate

was concentrated under vacuum. Then the residue was applied to column

chromatography to afford the purified product.

References

(1) Butler, M. S. J. Nat. Prod. 2004, 67 , 2141-2153.

(2) O'Hagan, D. Nat. Prod. Rep. 2000, 17 , 435-446.

(3) Hili, R.; Yudin, A. K. Nat. Chem. Biol. 2006, 2, 284-287.

(4) Yudin, A. K. Aziridines and Epoxides in Organic Synthesis 2006 .

(5) Hu, X. E. Tetrahedron 2004, 60 , 2701-2743.

(6) Krake, S. H.; Bergmeier, S. C. Tetrahedron 2010, 66 , 7337-7360.

(7) Dauban, P.; Malik, G. Angew. Chem., Int. Ed. 2009, 48 , 9026-9029.

(8) Coldham, I.; Hufton, R. Chem. Rev. 2005, 105 , 2765-2809.

(9) Pandey, G.; Banerjee, P.; Gadre, S. R. Chem. Rev. 2006, 106 , 4484-4517.

(10) Ungureanu, I.; Klotz, P.; Mann, A. Angew. Chem., Int. Ed. 2000, 39 , 4615-4617.

(11) Yadav, J. S.; Reddy, B. V. S.; Pandey, S. K.; Srihari, P.; Prathap, I. Tetrahedron

Lett. 2001, 42 , 9089-9092.

(12) Fan, J. M.; Gao, L. F.; Wang, Z. Y. Chem. Commun. 2009 , 5021-5023.

(13) Wender, P. A.; Strand, D. J. Am. Chem. Soc. 2009, 131 , 7528-7529.

(14) Kang, B. M.; Miller, A. W.; Goyal, S.; Nguyen, S. T. Chem. Commun. 2009 , 3928.

(15) Gandhi, S.; Bisai, A.; Prasad, B. A. B.; Singh, V. K. J. Org. Chem. 2007, 72 , 2133-

2142.

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(16) Ghorai, M. K.; Ghosh, K. Tetrahedron Lett. 2007, 48 , 3191-3195.

(17) Prasad, B. A. B.; Pandey, G.; Singh, V. K. Tetrahedron Lett. 2004, 45 , 1137-1141.

(18) Beller, M.; Bolm, C., Transition Metals for Organic Synthesis . 2nd ed.; Wiley-

VCH: Weinheim, 2004.

(19) Kelleher, S.; Quesne, P. Y.; Evans, P. Beilstein J. Org. Chem. 2009, 5.

(20) Ungureanu, I.; Bologa, C.; Chayer, S.; Mann, A. Tetrahedron Lett. 1999, 40 , 5315-

5318.

(21) Nakanishi, M.; Salit, A. F.; Bolm, C. Adv. Synth. Catal. 2008, 350 , 1835-1840.

(22) Yamada, Y.; Yamamoto, T.; Okawara, M. Chem. Lett. 1975 , 361-362.

156

CHAPTER 5: OXENE AND NITRENE CHEMISTRY OF Ni(0) MEDIATED BY

TRIS(3,5-DIMETHYLPYRAZOL-1-YL)METHANE

The oxo wall formalism rationalizes the scarcity of tetragonal oxo complexes for transition metals to the right of the iron triad to occupancy of π* orbitals, which reduces

metal-oxo bond order. 1 Nonetheless, a few late transition metal oxo complexes have been

2-7 reported. Also of interest in this regard are isolobal CR 2, NR, or PR moieties stabilized in linear Ni(II), 8 trigonal Ni(II) 9-12 and trigonal Ni(III) complexes. 13,14 Having prepared a

number of pseudotetrahedral nickel(II) complexes supported by anionic hydrotris-

(pyrazol-1-yl)borates (i.e., TpNi-X), 15 we noted isolobal and isoelectronic relationships to a hypothetical oxo-Ni(II) complex supported by tris(3,5-dimethylpyrazol-1-yl)methane

Me,Me II 16 III (i.e., [Tpm Ni {O}]), a neutral carbon-collared Tp analog. Dimeric [TpNi (µ-O)] 2 complexes have been isolated, 17-21 so it seemed plausible that a monomeric Tpm Me,Me -

supported analog could be obtained in a pseudotetrahedral geometry and subsequently

oxidized to Ni(III) or Ni(IV) complexes stabilized by enhanced oxonickel bond order. 22

Similar high-valent species have been invoked as intermediates in peroxide-driven epoxidations and hydroxylations. 23-26

We reasoned the most straightforward approach to [(Tpm Me,Me )Ni II (O)] or an

isolobal imido analog [(Tpm Me,Me )Ni II (NR)] would be addition of Tpm Me,Me to

0 27 [Ni (COD) 2], followed by oxo atom or nitrene group transfer. Therefore, meta -

chloroperoxybenzoic acid (mcpba), phenyl-N-tosylimidoiodinane (PhINTs; Ts = tosyl,

SO 2C6H4-4-CH 3) or 2-(tert-butylsulfonyl)iodosylbenzene (ArIO) were added to

0 [Ni (COD) 2] (COD = 1,5-cyclooctadiene) in THF in the presence of one equivalent of

157

Me,Me 0 Tpm . Our strategy was partially successful in that oxidation of [Ni (COD) 2] and

assembly of Tpm Me,Me -supported nickel(II) complexes occurred readily. However, the

targeted pseudotetrahedral species were not isolated. The Tpm Me,Me ligand exhibited a

marked propensity to support octahedral complexes arising from multiple ligand

additions, and the products obtained from the reagents just enumerated include

Me,Me II Ni Me,Me II II Ni [Tpm Ni (OH 2)(3-ClC 6H4CO 2)2] ( 6 ), [(Tpm )2Ni ][Ni (NHTs) 4] ( 7 ), and

Me,Me II Ni [Tpm Ni (OH) 2(OH 2)] ( 8 ), respectively. The syntheses and characterizations of these novel products are described herein, which adds to the small extant body of nickel- tris(pyrazolyl)methane coordination chemistry. 16,28-36

Experimental

General procedures . All materials obtained from commercial vendors were ACS reagent-grade or better and used as received, except for drying of solvents by routine techniques. The Tpm Me,Me ligand, 37 phenyl-N-tosyliminoiodinane (PhINTs), 38 and 2-(tert -

butylsulfonyl)iodosylbenzene (ArIO) 39 were prepared by literature procedures. All manipulations were carried out under an inert atmosphere of prepurified argon, either in a glovebox (MBraun Unilab) or using Schlenk techniques. 1H NMR data were recorded on

a Varian Unity 500 spectrometer and processed using the MestReNova 5.1 software suite

(Mestrelab Research, Santiago de Compostela, Spain); spectra were referenced internally

to the residual solvent resonance(s). UV-visible-NIR spectra were recorded on an Agilent

HP-8453 diode-array spectrophotometer. Elemental analyses were performed by Atlantic

Microlabs, Inc. (Norcross, GA).

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Me,Me II Ni 36 Preparation of [Tpm Ni (OH 2)Cl 2] ( 5 ). Anhydrous NiCl 2 (195 mg, 1.50

mmol) dissolved in MeOH (15 mL) was added to a solution of Tpm Me,Me (450 mg, 1.51

Ni mmol) in CH 2Cl 2 (20 mL). After brief stirring, removal of solvent under vacuum gave 5 as a green microcrystalline powder, which was recrystallized by slow evaporation of a

CH 3CN solution. Yield: 590 mg (1.32 mmol, 88%). Anal. Calc’d. (Found) for

Ni 1 C16 H25 Cl 2N6NiO 1.5 , 5 •½H 2O: C, 42.23 (42.15); H, 5.54 (5.57); N, 18.47 (18.53). H

NMR (CD 3CN, 295 K, δ ppm): 51.8 (3H, 4-H); -2.6 (9H, 5-Me); -8.7 (10H, 3-Me+CH).

1 H NMR (D 2O, 295 K, δ ppm): 54.6 (3H, 4-H); -2.3 (9H, 5-Me); -8.0 (1H, CH); -10.1

(9H, 3-Me).

Me,Me II Ni Preparation of [Tpm Ni (OH 2)(3-ClC 6H4CO 2)2] ( 6 ). A 1:1 mixture of m- chloroperoxybenzoic acid (51.8 mg, 0.30 mmol) and m-chlorobenzoic acid (47.0 mg,

0.30 mmol) were dissolved together in THF (10 mL) and slowly added to a solution of

0 Me,Me [Ni (COD) 2] (82.5 mg, 0.30 mmol) and Tpm (90.0 mg, 0.30 mmol) together in THF

(15 mL). The combined solutions turned light green. The solvent was stripped and the

Ni residue was washed with Et 2O. Green crystals of 6 •CH 2Cl 2•0.5C 6H14 were obtained by

dissolving the remaining solids in CH 2Cl 2 and layering with hexanes. Yield: 106 mg

Ni (0.13 mmol, 43% yield). Anal. Calc’d. (Found) for C30 H32 Cl 2N6NiO 5, 6 : C, 52.51

1 (53.22); H, 4.70 (4.63); N, 12.25 (11.79). H NMR (CD 3CN, 295 K, δ ppm): 44.6 (3H, 4-

H); 13.9 (2H, mcba); 10.9 (2H, mcba); 9.9 (2H, mcba); 7.6 (2H, mcba); -1.2 (9H, 5-Me);

1 -5.6 (1H, CH); -11.9 ppm (9H, 3-Me). H NMR (CD 2Cl 2, 295 K, δ ppm): 45.8 (3H, 4-H, species b); 43.6 (3H, 4-H, species a); 12.8 (2H, mcba, a); 10.9 (2H, mcba, a); 10.1 (sh,

2H, mcba, a); 9.5 (2H, mcba, b); 8.79 (4H, mcba, b); 7.9 (2H, mcba, a); 7.6 (2H, mcba,

159

b); -1.3 (9H, 5-Me, a); -2.2 (9H, 5-Me, b); -5.5 (1H, CH, a); -6.4 (1H, CH, b); -8.9 ppm

(9H+9H, 3-Me, a+b).

Me,Me II II Ni Preparation of [(Tpm )2Ni ][Ni (NHTs) 4] ( 7 ). A 1:1 mixture of

0 Me,Me [Ni (COD) 2] (110 mg, 0.39 mmol) and Tpm (120.0 mg, 0.40 mmol) were dissolved

together in THF (15 mL) and added slowly to a suspension of PhINTs (187 mg, 0.50

mmol) in THF (15 mL) at room temperature. The PhINTs eventually dissolved and the

solution turned purple. After stirring 20 min, a brown precipitate began to appear. After

stirring 4 h, solvent was removed under vacuum. The purple-brown solid was extracted

into CH 2Cl 2 (3 mL). The extracts were filtered, layered with diethyl ether and allowed to

stand at -37 °C. Purple crystals of 7Ni were isolated by filtration. Yield: 115 mg (0.08

Ni mmol, 42 %). Anal. Calc’d. (Found) for C 60 H80 N16 Ni 2O10 S4, 7 •2H 2O: C, 50.36

1 (50.53); H, 5.63 (5.55); N, 15.66 (15.48). H NMR (CD 3CN, 295 K, δ ppm): 54.4 (6H, 4-

H); 10.4 (8H, Ts); 8.8 (8H, Ts); 3.7 (12H, Ts); -2.8 (18H, 5-Me); -9.8 (18 H, 3-Me); -13.9

(2H, CH), -99.4 (4H, NHTs).

Me,Me II Ni 0 Preparation of [Tpm Ni (OH) 2(OH 2)] ( 8 ). A 1:1 mixture of [Ni (COD) 2]

(110 mg, 0.40 mmol) and Tpm Me,Me (120 mg, 0.40 mmol) were dissolved together in THF

(15 mL) and slowly added to a suspension of 2-(tert -butylsulfonyl)iodosylbenzene

(153mg, 0.45 mmol) in THF (2 mL) at room temperature. The resulting pale yellow- green solution was allowed to stir at room temperature for 4 hours. Solvent was then stripped and the pale yellow-green solid was dissolved in a minimal amount of CH 2Cl 2 and layered with n-hexane. The sample was kept at -37 ºC until light purple crystals of

Ni 8 •CH 2Cl 2 formed. Yield: 89 mg (0.18 mmol, 45%). Anal. Calc’d. (Found) for

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Ni 1 C17 H28 Cl 2N6NiO 3, 8 •CH 2Cl 2: C, 41.33 (41.92); H, 5.71 (4.92); N, 17.01 (16.90). H

NMR (CD 3CN, 295 K, δ ppm): 54.3 (3H, 4-H); -2.8 (9H, 5-Me); -9.7 (10H, 3-Me+CH).

Ni X-ray Crystallography . A colorless crystal of [{HC(C 5H7N2)3}NiCl 2(H 2O)] ( 5 )

was washed with the perfluoropolyether PFO-XR75 (Lancaster) and sealed under

nitrogen in a glass capillary. The sample was optically aligned on the four-circle of a

Siemens P4 diffractometer equipped with a graphite monochromator, a monocap

collimator, a Mo K α radiation source ( λ = 0.71073 Å), and a SMART CCD detector held at 5.082 cm from the crystal. The program SMART (version 5.6) 40 was used for diffractometer control, frame scans, indexing, orientation matrix calculations, least- squares refinement of cell parameters, and the data collection. All 1650 crystallographic raw data frames were read by program SAINT (version 5/6.0) 41 and integrated using 3D profiling algorithms. The resulting data were reduced to produce a total of 52862 reflections and their intensities and estimated standard deviations. A semi-empirical absorption correction was applied using the SADABS routine available in SAINT. 41,42

The data were corrected for Lorentz and polarization effects. A correction for secondary extinction was unnecessary. No evidence of crystal decomposition was observed. Data preparation was carried out by using the program XPREP, 40 and the structure was solved by a combination of direct methods and difference Fourier analysis with the use of

SHELXTL. 43 The crystallographic asymmetric unit contains two independent molecules.

The hydrogen atoms bound to a carbon atom were included as fixed contributions using a

riding model with isotropic temperature factors set at 1.2 (methine and aromatic) or 1.5

(methyl protons) times that of the adjacent carbon atom. The positions of the hydrogen

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atoms of the two coordinated water molecules were refined isotropically with the O-H

bond distances restrained to 0.85 ± 0.02 Å. The positions of the methyl hydrogen atoms

were optimized by a rigid rotating group refinement with idealized tetrahedral angles.

The linear absorption coefficient, atomic scattering factors, and anomalous dispersion

corrections were calculated from values found in the International Tables of X-ray

Crystallography. 44 Crystal and refinement information are summarized in Appendix 36; a thermal ellipsoid plot is shown in Figure 5.1 and relevant bond lengths and angles are listed in the caption.

Ni A blue crystal of [{HC(C 5H7N2)3}Ni(C 7H4ClO 2)2(H 2O)]•CH 2Cl 2•0.5C 6H14 (6 )

was placed onto the tip of a 0.1 mm diameter glass capillary and mounted on a CCD area

detector diffractometer for data collection at 173(2) K. 41 The data collection was carried out using MoK α radiation (graphite monochromator) with a frame time of 15 seconds and a detector distance of 4.9 cm. Final cell constants were calculated from strong reflections from the actual data collection after integration (SAINT). 41 The space group

P-1 was determined based on systematic absences and intensity statistics. The intensity

data were corrected for absorption and decay (SADABS). 42 The structure was solved by

direct methods and refined using Bruker SHELXTL. 43 All non-hydrogen atoms were

refined with anisotropic displacement parameters. All hydrogen atoms were placed in

ideal positions and refined as riding atoms with relative isotropic displacement

parameters. There was one dichloromethane per asymmetric unit that was ordered. There

was also a compositional disorder of at least two structural isomers of hexane on a

crystallographic inversion center; it appeared that n-hexane fills this site most of the time,

162

but 2-methyl-pentane was present as a substantial fraction. Attempts were made to model

this, but none was satisfactory. The disordered solvent was removed from the reported

structure by applying Platon/Squeeze. 45 The ‘hexanes’ solvent filled 199.6 Å 3 out of the

total 1893.3 Å3, or 10.54% of the unit cell volume. 51 electrons were found within this space, which corresponds approximately to one solvent ‘hexanes’ molecule per unit cell.

The R1 improved from ~0.08 to 0.0495 following the application of Platon/Squeeze and several cycles of least-squares refinement. The molecular formula is based on one hexane per unit cell. Finally, the librational motion of the meta -chloro-benzoate group appears to be an artifact of the hexane disorder. Crystal and refinement information are summarized in Appendix 37; a thermal ellipsoid plot is shown in Figure 5.3 and relevant bond lengths and angles are listed in the caption.

Ni Violet crystals of [{HC(C 5H7N2)3}2Ni][Ni(NH{SO 2C6H4-4-CH 3}) 4]•2MeCN (7 )

were obtained from a CD 3CN solution on standing. A single crystal was selected and

placed onto the tip of a 0.1 mm diameter glass capillary and mounted on a CCD area

detector diffractometer for a data collection at 123(2) K. 40 A preliminary set of cell constants was calculated from reflections harvested from three sets of 20 frames. These initial sets of frames were oriented such that orthogonal wedges of reciprocal space were surveyed. This produced initial orientation matrices determined from 246 reflections. The data collection was carried out using MoK α radiation (graphite monochromator) with a frame time of 15 seconds and a detector distance of 4.8 cm. A randomly oriented region of reciprocal space was surveyed to the extent of one sphere and to a resolution of 0.77

Å. Four major sections of frames were collected with 0.30º steps in ω at four different φ

163

settings and a detector position of -28º in 2 θ. Final cell constants were calculated from

2969 strong reflections from the actual data collection after integration (SAINT). 41 The

intensity data were corrected for absorption and decay (SADABS). 42 The structure was solved using Bruker SHELXTL 43 and refined using Bruker SHELXTL. 404 The space group P2 1/n was determined based on systematic absences and intensity statistics. A direct-methods solution was calculated which provided most non-hydrogen atoms from the E-map. Full-matrix least squares / difference Fourier cycles were performed which located the remaining non-hydrogen atoms. All non-hydrogen atoms were refined with anisotropic displacement parameters. All hydrogen atoms were placed in ideal positions and refined as riding atoms with relative isotropic displacement parameters. Both nickel atoms were found on different crystallographic inversion centers. In addition, one molecule of acetonitrile was found in a general position. In the dianion, the NHTs ligands form a ring of four hydrogen bonds in a closed set; the two unique hydrogen atoms in these hydrogen bonds were allowed to refine positionally with a common distance restraint. Crystal and refinement information are summarized in Appendix 38; a thermal ellipsoid plot is shown in Figure 5.6 and relevant bond lengths and angles are listed in the caption.

Results and Discussion

X-ray structures were previously reported for the sandwich dication

Me,Me II 2+ Me,Me [(Tpm )2Ni ] (Tpm , tris{3,5-dimethylpyrazol-1-yl)}methane) as the bis-

30 31 2- 32 (tetrafluoroborate), dibromide, and (NiCl 4) salts, as well as the half-sandwich

Me,Me II 2 1 33 complex [Tpm Ni (κ -NO 3)( κ -NO 3)]. Another half-sandwich complex

164

Me,Me II Ni [Tpm Ni (OH 2)Cl 2] ( 5 ) was previously reported, but its structure was not

determined. 36 Therefore, we repeated the synthesis of 5Ni and obtained its structure

(Figure 5.1) for the purpose of comparison to analogous products obtained herein ( vide infra ).

The structure of 5Ni consists of two independent molecules of

Me,Me II [Tpm Ni (OH 2)Cl 2] connected by intermolecular Cl ··· HO contacts in the range of

2.32(3)-2.52(3) Å, shorter than the sum of van der Waals radii. The metal-ligand bond

8 3 lengths are consistent with a d electron configuration ( A2g under ideal octahedral symmetry) in which both d σ* (i.e., e g) orbitals are singly occupied. The Ni-N bonds fall in a narrow range of 2.088(2)-2.167(2) Å; the nitrogen situated trans to the aquo ligand exhibits a slightly shorter average bond length, 2.10(1) Å than the nitrogens trans to the chlorides, 2.15(1) Å. The overall average Ni-N bond length of 2.13(3) Å can be

Me,Me II 2+ 30-32 compared to an averaged value of 2.10(1) Å in various salts of [(Tpm )2Ni ] ,

Me,Me II 1 2 33 and a range of 2.010(3)-2.135(3) Å in [Tpm Ni (κ -NO 3)( κ -NO 3)]. The Ni-OH 2 and Ni-Cl bond lengths average 2.09(1) and 2.41(1) Å, respectively.

To further elucidate the structure of 5Ni , we define a plane that includes both

chlorides and the two trans pyrazole nitrogens (i.e., N3, N5 on Ni1 and N9, N11 on Ni2).

The nickel atoms in both molecules of 5Ni reside within 0.015 Å of the least-squares mean. Within this “square” plane, the cis Cl-Ni-Cl bond angles are slightly opened,

93.16(2)° (Ni1) and 94.91(3)° (Ni2), while the N-Ni-N bond angles, constrained by the bite of the Tpm Me,Me chelate, are 83.06(8)° (at both Ni1 and Ni2). The cis Cl-Ni-N angles fall in a range of 90.11(6)°-92.64(6)°; thus, the cis bond angles within the N 2NiCl 2 plane

165

sum to an average value of 359(1)°. The aquo ligand is essentially orthogonal to this

plane, with four cis O-Ni-N and O-Ni-Cl bond angles ranging from 88.64(8)°-91.71(5)° with an average value of 90(1)°. However, the trans pyrazole nitrogen is also constrained from optimal octahedral coordination by the ligand bite. The trans N-Ni-OH 2 angle is non-linear, 172.29(8)° (N1-Ni1-O1) and 173.67(8)° (N7-Ni2-O7), bending away from the chlorides; the cis N-Ni-N and N-Ni-Cl bond angles range from 84.50(8)°-85.80(8)° and

93.44(6)°-96.42(6)°, respectively. Overall, all six cis N-Ni-N angles on the Tpm Me,Me ligand are constrained to a range of 83.06(8)-85.80(8). The trans N-Ni-Cl angles range from 173.07(6)°-174.99(6)°. Compared to the anionic boron-collared Tp Me,Me ligand,

which supports numerous 4- and 5-coordinate Ni(II) complexes with cis N-Ni-N angles

in excess of 90°, 12 the constrained bite and neutral charge of the TpmMe,Me ligand appear

to favor distorted octahedral coordination. This conclusion impacted our synthetic

0 Me,Me strategy of oxidizing [Ni (COD) 2] in the presence of Tpm with disparate oxene and

nitrene transfer reagents, which resulted in formation of a different octahedral Tpm Me,Me -

supported Ni(II) product complex in each case.

0 Me,Me A 1:1 mixture of [Ni (COD) 2] and Tpm dissolved in d 8-THF was examined by 1H NMR spectroscopy at room temperature (Figure 5.2). Observed resonances were

0 Me,Me assigned to intact [Ni (COD) 2], free Tpm and free COD. While partial solvation of

0 Me,Me [Ni (COD) 2] was observed, no interaction with Tpm was evident. A similar result

0 was observed in a previous study for addition of Tpm to [Ni (COD) 2], used to promote cross-coupling of aryl halides: Tpm was proposed to interact only with nickel(II) generated by oxidative addition. 46 We pursued a parallel strategy of adding mcbpa,

166

0 Me,Me PhINTs or ArIO to the [Ni (COD) 2]/Tpm mixture, intending to generate

pseudotetrahedral oxene and nitrene complexes from simple atom or group transfer (i.e.,

[Tpm Me,Me Ni II O]).

0 Me,Me Addition of mcpba to the d 8-THF solution of [Ni (COD) 2]/Tpm generated

multiple paramagnetic species as observed by 1H NMR spectroscopy. Co-addition of m-

Me,Me II chlorobenzoic acid gave cleaner conversion to [Tpm Ni (OH 2)(3-ClC 6H4CO 2)2]

Ni 0 Me,Me II (6 ). We expected that peroxidation of [Ni (COD) 2] would form [Tpm Ni (OH)(3-

ClC 6H4CO 2)] by oxidative addition (eqn. 1), with subsequent capture of the carboxylic acid impurity giving rise to 6Ni (eqn. 2). However, 6Ni was still formed by adding the carboxylic acid alone; hence, proton reduction by Ni(0) is competitive, leading to 6Ni by subsequent capture of carboxylate anions and H 2O (eqns. 3, 4).

0 II L+ Ni + RC(O)OOH LNi (OH)(O2CR) [1] II II LNi (OH)(O2CR) + RCO2H LNi (OH2)(O2CR)2 [2] 0 II L+ Ni + 2 RC(O)OH LNi (O2CR)2 + H2 [3] LNiII(O CR) + H O II [4] 2 2 2 LNi (OH2)(O2CR)2

The structure of 6Ni determined by X-ray crystallography (Figure 5.3) is

analogous to that of 5Ni , with κ1-carboxylato ligands in place of the chlorides. The Ni-

Ni Ni OH 2 bond length in 6 , 2.080(2) Å is similar to that of 5 , as are the Ni-N bond lengths, which range from 2.099(2)-2.153(2) Å. The Ni-N bond trans to the aquo ligand is slightly shorter than the two Ni-N bonds disposed trans to the anionic carboxylates. The

Ni-OC(O)R bond lengths are 2.046(2) (Ni1-O1) and 2.064(2) Å (Ni1-O3). The cis N-Ni-

167

N angles average 85(2)° in 6Ni , compared to 84(1)° in 5Ni . As in the structural analysis of

5Ni , a least-squares plane can be defined by the carboxylate oxygens and trans nitrogens

(N2, N6, O1, and O3). However, the nickel atom in 6Ni is displaced 0.104 Å out of this plane, towards the aquo ligand (O5) and away from the trans pyrazole (N4). Also unlike

5Ni , the trans N4-Ni1-O5 angle to the aquo ligand is nearly linear, 179.30(8)°, while the

trans N-Ni-O angles to the carboxylates are bent, 171.78° (N2-Ni1-O3) and 173.19(8)°

(N6-Ni1-O1). Again unable to fully span an octahedral face, the Tpm Me,Me ligand is

Ni displaced onto the N4-Ni1-OH 2 axis in 6 , rather than into the orthogonal N 2O2 plane, as

in 5Ni . This difference may reflect disparate hydrogen bonding of the aquo ligand. While

5Ni exhibits intermolecular Cl•••HO contacts, the carboxylato ligands of 6Ni support short

intramolecular hydrogen bonds between the unligated oxygens and the aquo protons,

1.82(3) Å (H5D•••O2) and 1.84(3) Å (H5E•••O4).

1 Ni Ni H NMR spectra of 5 and 6 in CD 3CN solution are consistent with paramagnetic ( S = 1) electron configurations resulting from octahedral coordination of d 8 nickel(II). The spectrum of 5Ni exhibits three signals in a 3:9:10 intensity ratio at 51.8, -

2.6 and -8.7 ppm, respectively assigned to the 4-H, 5-Me, and 3-Me pyrazolyl resonances respectively, with the latter overlapping the methine signal (Figure 5.4A). The spectrum of 6Ni contains analogous Tpm Me,Me ligand resonances at 44.6, -1.2 and -11.9 ppm, with a resolved methine resonance at -5.6 ppm; four additional resonances at 13.9, 10.9, 9.9, and

7.6 ppm are assigned to the m-chlorophenyl substituents of the carboxylate ligands

(Figure 5.4B). The slight paramagnetic shifts indicate the carboxylates remain coordinated to nickel(II), and the relative broadness of the two middle resonances is

168

consistent with assignment to the inequivalent ortho protons. Unlike 5Ni , complex 6Ni is soluble in less polar solvents such as CD 2Cl 2, in which the spectrum exhibits a second, somewhat broader set of resonances (labeled “b” in Figure 5.4C). This second species is

Me,Me II assigned as the intact complex [Tpm Ni (OH 2)(3-ClC 6H4CO 2)2,], while the species

observed in CH 3CN may result from solvation of the aquo ligand, resulting in a

Me,Me II 2 dehydrated [Tpm Ni (3-ClC 6H4CO 2)2] derivative with at least one κ -carboxylato ligand.

Both 5Ni and 6Ni exhibit solution-phase UV-Vis spectra consistent with octahedral

coordination of a d 8 Ni(II) ion (Figure 5). 34 The spectrum of 5Ni in MeOH is very similar to the previously reported aqueous spectrum (wherein solvolysis of the chlorides is

36 3 3 3 expected), with spin-allowed bands at 996 nm ( T2{F} ← A2) and 624 nm ( T1{F} ←

3 1 3 A2) and a spin forbidden band ( E ← A2) appearing as a weak shoulder at 741 nm.

-1 -1 Alignment on the Tanabe-Sugano diagram gives ∆O = 10,000 cm , B = 880 cm , and

3 3 places the third spin-allowed ( T1{P} ← A2) transition at 360 nm, where it is obscured

Ni by the tail of strong UV bands. The spectrum of 6 in non-polar CH 2Cl 2 is modestly red-

- shifted, consistent with its neutral charge and the spectrochemical series (ROH > RCO 2 ),

while a UV shoulder with partially resolved fine structure reflects the presence of the

aromatic substituents on the carboxylato ligands.

0 Me,Me Oxidation of [Ni (COD) 2]/Tpm with a suspension of the nitrene precursor

PhINTs in THF gave a dark violet homogeneous solution that yielded a brown precipitate

Me,Me II on standing. This product was recrystallized and identified as [(Tpm )2Ni ]-

II Ni [Ni (NHTs) 4] (7 ). Proton reduction by [Ni(COD) 2] is discounted in this reaction, since

169

0 the PhINTs reagent dissolved and a control mixture of 1:1:1 [Ni (COD) 2]:

Me,Me 1 Tpm :TsNH 2 monitored in d 8-THF by H NMR spectroscopy gave no evidence of

0 reactivity. Instead, the initial reaction of [Ni (COD) 2] and PhINTs may produce the intended imido complex product, namely pseudotetrahedral [Tpm Me,Me Ni II NTs] (eqn. 5).

However, subsequent addition of free amine, initially present as an impurity in the nitrene precursor or liberated by its hydrolysis, would form the neutral bis(amido) complex

Me,Me II [Tpm Ni (NHTs) 2], a coordination isomer of the observed product salt (eqns. 6-8).

L+ Ni0 + PhINTs LNiII(NTs) + PhI [5] [6] PhINTs + H2O PhIO + TsNH2 II II [7] LNi (NTs) + TsNH2 LNi (NHTs)2 2 LNiII(NHTs) [L NiII][NiII(NHTs) ] [8] 2 2 4

Me,Me II 2+ The structure of the [(Tpm )2Ni ] dication determined by X-ray crystallography is unremarkable (Figure 5.6). The pseudo-octahedral (ideally D 3d ) nickel atom sits on an inversion center, so only half of the sandwich structure is unique. The average Ni-N bond length is 2.106(6) Å and the intra- and inter-ligand cis N-Ni-N bond

angles are 85.3(6)° and 94.7(6)°, respectively, equivalent to three previous structures with

30-32 II 2- different counterions. In constrast, the square-planar [Ni (HNTs) 4] dianion is quite unique. A large number of Ni(II) complexes with N-substituted sulfonamidato donors

have been reported, but these are typically incorporated into chelating ligands; 47-49 only

- two previous examples feature primary monodentate [HNS(O) 2R] anions, and these were

neutral octahedra. 50,51 The nickel atom sits on a separate inversion center. The two unique

170

Ni-N bond lengths are effectively equivalent, 1.922(2) Å (Ni2-N7) and 1.921(2) Å (Ni2-

N8), and the cis N-Ni-N bond angles are nearly square, 92.09(6)° (N7-Ni2-N8) and

87.91(6)° (N7-Ni2-N8 ′). The tosyl substituents also support a unique collar of N-

H•••O=S hydrogen bonds around the NiN 4 plane, 2.11(2) (O2•••H8A) and 2.13(2) Å

(O3•••H7B).

The product salt 7Ni was soluble only in polar solvents. Observed paramagnetic

Me,Me II 2+ shifts of resonances for the [(Tpm )2Ni ] dication in CD 3CN solution were

consistent with a previous report. 31 Notwithstanding the square-planar structure observed

in the solid state, the 1H NMR resonances of the dianion were also consistent with paramagnetism in CD 3CN. The tosyl resonances (labeled “c” in Figure 5.4D) were

shifted slightly downfield (10.4, 8.8 and 3.7 ppm), while a pronounced upfield peak (at -

99.4 ppm) was tentatively assigned to the amide protons. The UV-Vis-NIR spectrum in

CH 3CN (Figure 5.5) appeared to be consistent with a superposition of two octahedral species, presumably reflecting solvent coordination to the dianion. Similar to a previous

34 3 3 report, the lowest-energy ligand field transition ( T2{F} ← A2) of the dication

Me,Me II 2+ -1 [(Tpm )2Ni ] was observed at 869 nm (11,500 cm ), while the split band centered

-1 3 roughly at 560 nm (17,900 cm ) was assigned to the second ligand field band ( T1(F) ←

3 A2). A second set of bands arising from the dianion was evident, with a slight blue shift to 759 nm (13,200 cm -1) and 442 nm (22,700 cm -1); the latter appeared to be split, overlapping the higher energy peak of the dication as a shoulder.

No reaction was obtained from addition of insoluble PhIO to a 1:1 mixture of

0 Me,Me t [Ni (COD) 2]/Tpm in THF. However, the substituted analog 2- BuSO 2C6H4IO readily

171

0 1 dissolved and oxidized the [Ni (COD) 2]. A H NMR spectrum of the crude reaction

mixture extracted into CDCl 3 (Figure 5.4E) revealed the presence of free COD and the

reduced aryl iodide. A major paramagnetic species was observed that exhibited

resonances similar to the other octahedral complexes already described (Figure 5.4A-C),

indicating that Tpm Me,Me was bound to nickel(II) in a half-sandwich complex. Elemental analysis of pale purple crystals isolated from the reaction mixture indicated a molecular mass of 498(1) amu, extrapolated from the nitrogen analysis and normalized to the six atoms of the Tpm Me,Me ligand. The excess mass beyond the target complex

Me,Me [Tpm Ni(O)] (373 amu) was tentatively ascribed to addition of two H 2O molecules

(eqns. 9-11) and a lattice CH 2Cl 2 molecule, giving a formulation of

Me,Me II Ni Ni [Tpm Ni (OH 2)(OH) 2]•CH 2Cl 2 (8 •CH 2Cl 2, 494 amu). Since 8 appears to be an

octahedral complex analogous to 5Ni or 6Ni , further structural characterization of this product was not pursued.

L+ Ni0 + ArIO LNiII(O) + ArI [9] II LNiII(OH) [10] LNi (O) + H2O 2 II II LNi (OH)2 + H2O LNi (OH2)(OH)2 [11]

The goal of this work was synthesis of hypothetical pseudotetrahedral species

[Tpm Me,Me Ni II =E] (E = O, NTs), by oxene atom or nitrene group transfer to

Me,Me 0 1 [Tpm Ni (COD)]. H NMR spectroscopy of a d 8-THF reaction solution clearly

Me,Me 0 establishes that Tpm does not add to partial solvated [Ni (COD) 2]. Addition of

mcpba, PhINTs or ArIO results in two-electron oxidation and assembly of Tpm Me,Me

172 complexes, but the reactivity does not yield the desired pseudotetrahedral products.

Instead, the Tpm Me,Me ligand exhibits a marked propensity to favor octahedral nickel(II), which seems to arise from a relatively constrained bite. This abets further addition of fragments derived from the oxidizing precursors, either carboxylic acid, tosylamine, or

Me,Me Me,Me II H2O, respectively. The obtained octahedral Tpm complexes, [Tpm Ni (OH 2)(3-

Ni Me,Me II II Ni Me,Me II ClC 6H4CO 2)2] ( 6 ), [(Tpm )2Ni ][Ni (NHTs) 4] ( 7 ), and [Tpm Ni (OH) 2(OH 2)]

(8Ni ) respectively, add to the scope of nickel-tris(pyrazolyl)methane coordination chemistry. Moreover, there is evidence that the desired oxidative oxene and nitrene transfer chemistry may occur using hypervalent iodonium ylides. Thus, it will be worth exploring in future work whether substitution of other oxidative substrates and modification of the supporting scorpionate ligand would enable isolation of pseudotetrahedral oxo and imido complexes as kinetic products of this reactivity.

173

Cl2 N9 N1 O2 Ni1 Cl1 N11 N3 Cl4

Ni2 O1 N7 N5 Cl3

Figure 5.1. Thermal ellipsoid plot (50% ellipsoids) of 5Ni . Bond lengths (Å): Ni1-N1, 2.088(2); Ni1-N3, 2.147(2); Ni1-N5, 2.167(2); Ni1-Cl1, 2.426(1); Ni1-C12, 2.420(1); Ni1-O1, 2.078(2); C11 ··· H2a, 2.316; C12 ··· H2b, 2.518; Ni2-N7, 2.108(2); Ni2-N9, 2.136(2); Ni2-N11, 2.159(2); Ni2-Cl3, 2.400(1); Ni2-Cl4, 2.408(1); Ni2-O2, 2.093(2); C13 ··· H1a, 2.410; C14 ··· H1b, 2.426. Bond angles (°): N1-Ni1-N3, 84.50(8); N1-Ni1-N5, 85.80(8); N1-Ni1-Cl1, 94.28(6); N1-Ni1-Cl2, 96.42(6); N3-Ni1-N5, 83.06(8); N3-Ni1- O1, 89.54(8); N3-Ni1-Cl2, 92.64(6); N5-Ni1-O1, 88.64(8); N5-Ni1-Cl1, 91.17(6); O1- Ni1-Cl1, 91.17(6); O1-Ni1-Cl2, 88.71(6); Cl1-Ni1-Cl2, 93.16(2); N1-Ni1-O1, 172.29(8); N3-Ni1-Cl1, 174.17(6); N5-Ni1-Cl2, 174.97(6); N7-Ni2-N9, 84.87(8); N7-Ni2-N11, 85.49(8); N7-Ni2-Cl3, 93.44(6); N7-Ni2-Cl4, 94.29(6); N9-Ni2-N11, 83.06(8); N9-Ni2- O2, 89.58(7); N9-Ni2-Cl4, 91.93(6); N11-Ni2-O2, 90.84(8); N11-Ni2-Cl3, 90.11(6); O2- Ni2-Cl3, 91.71(5); O2-Ni2-Cl4, 88.92(6); Cl3-Ni2-Cl4, 94.91(3); N7-Ni2-O2, 173.67(8); N9-Ni2-Cl3, 173.07(6); N11-Ni2-Cl4, 174.99(6).

174

(C)

s s

(B)

(A)

10 9 8 7 6 5 4 3 2 1 0

δδδ (ppm)

1 Me,Me 0 Figure 5.2. H NMR spectra (d 8-THF, 295 K): (A), 1:1 Tpm and [Ni (COD) 2]; (B), free Tpm Me,Me ; (C), free COD. Peaks due to residual solvent are marked “s”.

175

O4 O2

O3 O1 Ni1 N4

N6 N2

Figure 5.3. Thermal ellipsoid plot of 6Ni (50% probability). Bond lengths (Å): Ni1-N2, 2.129(2); Ni1-N4, 2.099(2); Ni1-N6, 2.153(2); Ni1-O1, 2.046(2); Ni1-O3, 2.064(2); Ni1- O5, 2.080(2); O2 ·· H5d, 1.823; O4 ·· H5e, 1.838. Bond angles (°): N2-Ni1-N4, 84.25(8); N2-Ni1-N6, 83.75(8); N2-Ni1-O1, 90.36(8); N2-Ni1-O5, 96.44(8); N4-Ni1-N6, 87.18(8); N4-Ni1-O1, 88.83(8); N4-Ni1-O3, 88.16(8); N6-Ni1-O3, 92.75(8); N6-Ni1-O5, 92.72(8); O1-Ni1-O3, 92.63(8); O1-Ni1-O5, 91.33(8); O3-Ni1-O5, 91.15(7); N2-Ni1-O3, 171.78(8); N4-Ni1-O5, 179.30(8); N6-Ni1-O1, 173.19(8).

176

e ed ~ ~~ s d (E)

c s c (D) c * * b s b (C) a b a+b b a a ab * s (B)

* * s ~ 5 (A) 3 4 *

60 55 50 45 15 10 5 0 -5 -10 -15

δδδ (ppm)

1 Ni Ni Figure 5.4. H NMR spectra (295 K): (A), solvated 5 in wet CD 3CN; (B), 6 in Ni Ni Ni CD 3CN; (C), 6 in CD 2Cl 2; (D), 7 in CD 3CN; (E), crude products including 8 from 0 Me,Me t reaction of 1:1:1 [Ni (COD) 2]:Tpm :2- BuSO 2C6H4IO in THF, extracted into CDCl 3. Peaks due to residual solvent are marked “s”; lattice solvents (CH 2Cl 2, hexane) are denoted with an asterisk (*). In (A) and (E), tall peaks are truncated (~) for clarity. In (A), pyrazole resonances of 5Ni are labeled by position. In (C), two independent sets of resonances for 6Ni are labeled (a, b). In (D), resonances of tosyl substituents of 7Ni are t labeled (c). In (E), resonances of BuSO 2C6H4I and free COD are labeled (d) and (e), respectively.

177

) 40 -1

cm 30 -1 (M ε ε ε ε 20

0 400 500 600 700 800 900 1000

λλλ (nm)

Ni Ni Figure 5.5. UV-Vis-NIR spectra (295 K) of solvated 5 in CH 3OH (solid line), 6 in Ni CH 2Cl 2 (dashed line, ---) and 7 in CH 3CN (dotted line, •••).

178

N2 N6 N7 N8

Ni1 Ni2 N6 N8 N2 N7

Figure 5.6. Thermal ellipsoid plot of 7Ni (50% probability). Hydrogen atoms omitted for clarity, except for amides. Bond lengths (Å): Ni1-N2, 2.102(2); Ni1-N4, 2.113(1); Ni1- N6, 2.102(1); Ni2-N7, 1.922(2); Ni2-N8, 1.921(2); O2•••H8A, 2.11(2); O3•••H7B, 2.13(2). Bond angles (°): N2-Ni1-N4, 85.37(5); N2-Ni1-N6, 85.94(6); N4-Ni1-N6, 84.65(5); N2-Ni1-N2 ′, 180; N2-Ni1-N4 ′, 94.63(5); N2-Ni1-N6 ′, 94.06(6); N4-Ni1-N4', 180; N4-Ni1-N6 ′, 95.35(5); N6-Ni1-N6 ′, 180; N7-Ni2-N8, 92.09(6); N7-Ni2-N8 ′, 87.91(6); N7-Ni2-N7 ′, 180; N8-Ni2-N8 ′, 180.

179

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184

APPENDIX 1: NMR SPECTRUM OF 2

2-phenyl-1-(toluene-4-sulfonyl)-aziridine 1 2 (Table 3.3, entry 1)

1 H NMR (300 MHz, CDCl 3): δ 7.85 (d, J = 8.1 Hz, 2H), 7.36 – 7.17 (m, 7H), 3.76 (dd, J

= 7.1, 4.5 Hz, 1H), 2.96 (d, J = 7.2 Hz, 1H), 2.41 (s, 3H), 2.37 (d, J = 4.4 Hz, 1H).

1H NMR spectra for 2 (Table 3.3, entry 1) 7.86 7.84 7.32 7.30 7.28 7.26 7.24 7.21 7.20 7.19 3.78 3.76 3.75 3.74 2.98 2.95 2.41 2.37 2.36 1.99 7.60 1.00 1.05 3.26 1.10

185

APPENDIX 2: NMR SPECTRUM OF 52

1-(toluene-4-sulfonyl)-2-(4-trifluoromethyl-phenyl)-aziridine 2 52 (Table 4.1, entry 4)

Yield: 65%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.85 (d, J = 8.2 Hz, 2H), 7.53 (d, J = 8.1 Hz, 2H), 7.32 (d,

J = 8.0 Hz, 4H), 3.79 (dd, J = 7.0, 4.4 Hz, 1H), 3.00 (d, J = 7.2 Hz, 1H), 2.42 (s, 3H),

2.35 (d, J = 4.3 Hz, 1H).

1H NMR spectra for 52 (Table 4.1, entry 4)

186

APPENDIX 3: NMR SPECTRUM OF 53

2-(4-nitro-phenyl)-1-(toluene-4-sulfonyl)-aziridine1 53 (Table 4.1, entry 5)

Yield: 64%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 8.12 (d, J = 8.6 Hz, 2H), 7.84 (d, J = 8.2 Hz, 2H), 7.35

(dd, J = 15.4, 8.4 Hz, 4H), 3.82 (dd, J = 7.1, 4.3 Hz, 1H), 3.02 (d, J = 7.2 Hz, 1H), 2.42

(s, 3H), 2.35 (d, J = 4.2 Hz, 1H).

1H NMR spectra for 53 (Table 4.1, entry 5) 8.14 8.11 7.83 7.39 7.37 7.34 7.32 3.83 3.82 3.81 3.80 3.03 3.01 2.42 2.36 2.35 1.99 1.96 4.02 0.98 1.00 3.20 1.09

187

APPENDIX 4: NMR SPECTRUM OF 17

3-phenyl-1-(toluene-4-sulfonyl)-aziridine-2-carboxylic acid, methyl ester 1 17 (Table 3.3,

entry 6)

CO2Me NTs

Yield: 46%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.74 (d, J = 8.2 Hz, 2H), 7.32 – 7.17 (m, 7H), 4.41 (d, J =

3.9 Hz, 1H), 3.83 (s, 3H), 3.50 (d, J = 3.9 Hz, 1H), 2.38 (s, 3H).

1H NMR spectra for 17 (Table 3.3, entry 6) 7.76 7.73 7.29 7.28 7.26 7.23 4.41 4.40 3.83 3.50 3.49 2.38 1.99 7.25 0.96 2.97 0.99 3.17

188

APPENDIX 5: NMR SPECTRUM OF 15

Cis-2,3-diphenyl-1-(toluene-4-sulfonyl)-aziridine 1 15 (Table 3.3, entry 4)

White solid.

1 H NMR (300 MHz, CDCl 3): δ 7.89 (d, J = 8.2 Hz, 2H), 7.28 (d, J = 8.2 Hz, 2H), 7.08 –

7.01 (m, 6H), 7.01 – 6.91 (m, 4H), 4.15 (s, 2H), 2.37 (s, 3H).

1H NMR spectra for 15 (Table 3.3, entry 4) 7.90 7.87 7.29 7.27 7.05 7.04 7.03 6.98 6.97 6.96 4.15 2.37 1.97 2.14 5.92 4.04 1.99 3.10

189

APPENDIX 6: NMR Spectra OF 16

N-(1,2-diphenyl-vinyl)-4-methyl-benzenesulfonamide 16 (Table 3.3, entry 5)

Yield: 51%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.71 (d, J = 8.1 Hz, 2H), 7.38 – 7.29 (m, 5H), 7.26 – 7.18

(m, 3H), 7.09 (d, J = 7.7 Hz, 2H), 6.96 – 6.86 (m, 2H), 6.79 (d, J = 11.6 Hz, 1H), 6.26 (d,

J = 11.7 Hz, 1H), 2.44 (s, 3H).

13 C NMR (75 MHz, CDCl 3): δ 144.0, 139.4, 136.8, 136.4, 129.9, 129.6, 129.4, 128.4,

128.2, 127.1, 126.8, 126.6, 126.2, 120.3, 21.6.

190

1H NMR (top) and 13 C NMR (bottom) spectra for 16 (Table 3.3, entry 5) 7.72 7.70 7.35 7.21 7.11 7.08 6.93 6.81 6.77 6.28 6.24 2.44

NHTs 1.96 5.21 3.69 2.12 2.00 0.97 1.04 3.19

NHTs

191

COSY spectrum for 16 (Table 3.3, entry 5) f1 (ppm) f1

192

APPENDIX 7: NMR SPECTRUM OF 12

7-(toluene-4-sulfonyl)-7-aza-bicyclo[4.1.0]heptanes1 12 (Table 3.3, entry 2)

White solid.

1 H NMR (300 MHz, CDCl 3): δ 7.84 (d, J = 8.1 Hz, 2H), 7.35 (d, J = 8.0 Hz, 2H), 3.00 (s,

2H), 2.46 (s, 3H), 1.81 (m, 4H), 1.42 – 1.25 (m, 4H).

1H NMR spectra for 12 (Table 3.3, entry 2) 7.85 7.83 7.36 7.33 3.00 2.46 1.83 1.81 1.79 1.44 1.39 1.25 1.99 2.16 2.03 3.39 4.26 4.98

193

APPENDIX 8: NMR SPECTRUM OF 13

N-cyclohex-2-enyl-4-methyl-benzenesulfonamide 3 13 (Table 3.3, entry 2)

White solid.

1 H NMR (300 MHz, CDCl 3): δ 7.70 (d, J = 8.0 Hz, 2H), 7.23 (d, J = 7.9 Hz, 2H), 5.77 –

5.62 (m, 1H), 5.35 – 5.20 (m, 1H), 4.38 (d, J = 8.0 Hz, 1H), 3.85 – 3.64 (m, 1H), 2.36 (s,

3H), 1.91 – 1.42 (m, 6H).

1H NMR spectra for 13 (Table 3.3, entry 2) 7.72 7.69 7.25 7.22 5.71 5.68 5.29 5.26 4.39 4.37 3.75 2.36 1.86 1.69 1.67 1.53 1.51 1.49 1.99 2.20 1.00 0.97 0.99 1.01 3.30 6.94

194

APPENDIX 9: NMR SPECTRUM OF 14

3-(toluene-4-sulfonyl)-3-aza-tricyclo[3.2.1.0 2,4exo ]octane 1 14 (Table 3.3, entry 3)

51% yield, white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.73 (d, J = 8.2 Hz, 2H), 7.25 (d, J = 8.1 Hz, 2H), 2.84 (s,

2H), 2.37 (s, 5H), 1.39 (m, 3H), 1.16 (m, 2H), 0.68 (d, J = 10.0 Hz, 1H).

1H NMR spectra for 14 (Table 3.3, entry 3)

8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 δ (ppm)

195

APPENDIX 10: NMR SPECTRUM OF 32

4-methyl-N-phenyl-benzenesulfonamide 4 32 (Table 3.7, entry 1)

Yield: 45%; pale pink solid.

1 H NMR (300 MHz, CDCl 3): δ 7.59 (d, J = 8.0 Hz, 2H), 7.20 – 7.09 (m, 4H), 7.08 – 6.92

(m, 3H), 6.74 (br, 1H), 2.30 (s, 3H).

1H NMR spectra for 32 (Table 3.7, entry 1) 7.60 7.58 7.13 7.02 6.98 6.74 2.30 1.99 3.72 3.11 1.00 3.12

196

APPENDIX 11: NMR SPECTRA OF 45

4-methyl-N-(2,4,6-trimethyl-phenyl)-benzenesulfonamide 45 (Table 3.7, entry 8)

Yield: 81%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.64 (d, J = 8.1 Hz, 2H), 7.27 (d, J = 8.4 Hz, 2H), 6.85 (s,

2H), 6.01 (br, 1H), 2.45 (s, 3H), 2.27 (s, 3H), 2.03 (s, 6H).

13 C NMR (75 MHz, CDCl 3): δ 143.7, 138.2, 137.7, 130.2, 129.7, 127.5, 21.7, 21.1, 18.8.

197

1H NMR (top) and 13 C NMR (bottom) spectra for 45 (Table 3.7, entry 8)

198

APPENDIX 12: NMR SPECTRUM OF 39 AND 40

N-(2,5-dimethyl-phenyl)-4-methyl-benzenesulfonamide 39 and 4-methyl-N-(4-methyl- benzyl)-benzenesulfonamide 5 40 (Table 3.7, entry 5)

Based on 1H NMR, a mixture of aromatic and benzylic insertion product 39 and 40 was

formed in a ratio of 6.1:1; combined yield: 66%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.53 (d, J = 8.2 Hz, 2H), 7.13 (d, J = 8.2 Hz, 2H), 7.09 (s,

1H), 6.87 (d, J = 7.7 Hz, 1H), 6.80 (d, J = 7.7 Hz, 1H), 6.35 (br, 1H), 2.31 (s, 3H), 2.19

(s, 3H), 1.84 (s, 3H).

1 H NMR (300 MHz, CDCl 3): δ 7.70 (d, J = 8.2 Hz, 2H), 7.23 (d, J = 8.2 Hz, 2H), 7.02 (s, 4H), 4.68 (br, 1H), 4.00 (d, J = 6.1 Hz, 2H), 2.36 (s, 3H), 2.23 (s, 3H).

199

1H NMR spectra for the mixture of 39 (major) and 40 (minor) (Table 3.7, entry 5) 7.71 7.68 7.52 7.18 7.12 7.00 6.86 6.79 6.35 4.68 4.01 3.99 2.36 2.31 2.23 2.19 1.84

NHTs

39 0.38 2.12 0.42 2.09 1.08 0.75 1.07 1.07 1.00 0.17 0.36 0.61 3.15 0.61 2.97 3.34

200

APPENDIX 13: NMR SPECTRUM OF 43 AND 44

N-(2,4-dimethyl-phenyl)-4-methyl-benzenesulfonamide 43 and N-(2,6-dimethyl-phenyl)-

4-methyl-benzenesulfonamide 44 (Table 3.7, entry 7)

Based on 1H NMR, a mixture of was 43 and 44 formed in a ratio of 4.9:1; combined yield: 74%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.63 (d, J = 8.2 Hz, 2H), 7.24 (d, J = 8.1 Hz, 2H), 7.17 (d,

J = 8.0 Hz, 1H), 6.98 – 6.88 (m, 2H), 6.53 (br, 1H), 2.42 (s, 3H), 2.28 (s, 3H), 1.99 (s,

3H).

1 H NMR (300 MHz, CDCl 3): δ 7.63 (d, J = 8.2 Hz, 2H), 7.24 (d, J = 8.1 Hz, 2H), 7.12 – 7.07 (m, 1H), 7.06 – 6.99 (m, 2H), 6.29 (br, 1H), 2.45 (s, 3H), 2.07 (s, 6H).

201

1H NMR spectra for the mixture of 43 (major) and 44 (minor) (Table 3.7, entry 7) 7.65 7.62 7.25 7.08 7.04 7.02 6.96 6.92 6.53 6.29 2.45 2.42 2.28 2.07 1.99

NHTs

44 2.28 2.23 1.01 0.20 0.42 2.01 1.00 0.16 0.58 2.91 2.83 1.09 3.10

202

APPENDIX 14: NMR SPECTRUM OF 41 AND 42

N-(3,4-dimethyl-phenyl)-4-methyl-benzenesulfonamide 41 and N-(2,3-Dimethyl-phenyl)-

4-methyl-benzenesulfonamide 42 (Table 3.7, entry 6)

Based on 1H NMR, a mixture of 41 and 42 was formed in a ratio of 4:1; combined yield:

63%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.70 (d, J = 8.2 Hz, 2H), 7.23 (d, J = 8.1 Hz, 2H), 7.07 (s,

1H), 6.98 (d, J = 8.0 Hz, 1H), 6.90 (br, 1H), 6.83 (dd, J = 8.0, 1.8 Hz, 1H), 2.39 (s, 3H),

2.18 (s, 6H).

1 H NMR (300 MHz, CDCl 3): δ 7.65 (d, J = 8.2 Hz, 2H), 7.23 (d, J = 8.1 Hz, 2H), 7.06 – 7.00 (m, 3H), 6.71 (br, 1H), 2.42 (s, 3H), 2.23 (s, 3H), 1.99 (s, 3H).

203

1H NMR spectra for the mixture of 41 (major) and 42 (minor) (Table 3.7, entry 6) 7.72 7.69 7.66 7.63 7.25 7.22 7.07 7.05 7.04 7.03 7.01 6.99 6.97 6.90 6.85 6.84 6.82 6.82 6.71 2.42 2.39 2.18 1.99 2.01 0.59 2.60 1.00 0.79 0.97 1.00 0.98 0.25 0.79 2.95 0.95 6.26 0.85

204

APPENDIX 15: NMR SPECTRUM OF 37 AND 38

N-(4-isopropyl-phenyl)-4-methyl-benzenesulfonamide 37 and 4-methyl-N-(1-methyl-1- phenyl-ethyl)-benzenesulfonamide 3 38 (Table 3.7, entry 4)

Based on 1H NMR, a mixture of para aromatic and benzylic insertion product 37 and 38

was formed in a ratio of 1:1.1; combined yield: 57%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.50 (d, J = 8.1 Hz, 2H), 7.27 – 7.20 (m, 2H), 7.01 (d, J =

8.4 Hz, 2H), 6.90 (d, J = 8.2 Hz, 2H), 6.69 (br, 1H), 2.85 – 2.66 (m, 1H), 2.31 (s, 3H),

1.11 (d, J = 6.9 Hz, 6H).

1 H NMR (300 MHz, CDCl 3): δ 7.58 (d, J = 8.2 Hz, 2H), 7.17 – 7.05 (m, 7H), 5.02 (br,

1H), 2.31 (s, 3H), 1.55 (s, 6H).

205

1H NMR spectra for the mixture of 37 and 38 (Table 3.7, entry 4) 7.60 7.57 7.51 7.48 7.16 7.07 6.89 6.69 5.02 2.82 2.80 2.78 2.75 2.73 2.71 2.68 2.31 1.55 1.12 1.10 2.27 1.91 2.24 7.48 1.96 2.03 0.87 0.94 1.13 6.38 6.00 6.17

206

APPENDIX 16: NMR SPECTRUM OF 35 AND 36

N-(4-ethyl-phenyl)-4-methyl-benzenesulfonamide 35 and 4-methyl-N-(1-phenyl-ethyl)- benzenesulfonamide 5 36 (Table 3.7, entry 3)

Based on 1H NMR, a mixture of para aromatic and benzylic insertion product 35 and 36

was formed in a ratio of 1:1.1; combined yield: 62%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.68 (d, J = 8.3 Hz, 2H), 7.26 – 7.24 (m, 2H), 7.07 (d, J =

8.4 Hz, 2H), 7.01 (d, J = 8.5 Hz, 2H), 6.91 (br, 1H), 2.59 (q, J = 7.5 Hz, 2H), 2.41 (s,

3H), 1.20 (t, J = 7.6 Hz, 3H).

1 H NMR (300 MHz, CDCl 3): δ 7.65 (d, J = 8.0 Hz, 2H), 7.24 – 7.19 (m, 5H), 7.13 – 7.10

(m, 2H), 5.11 (d, J = 7.0 Hz, 1H), 4.49 (p, J = 6.9 Hz, 1H), 2.41 (s, 3H), 1.45 (d, J = 6.9

Hz, 3H).

207

1H NMR spectra for the mixture of 35 and 36 (Table 3.7, entry 3)

NHTs 36

8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 δ (ppm)

208

APPENDIX 17: NMR SPECTRUM OF 34 AND 35

4-methyl-N-p-tolyl-benzenesulfonamide 6 34 and 4-methyl-N-o-tolylbenzenesulfonamide 6

33 (Table 3.7, entry 2)

Based on 1H NMR, a mixture of 34 and 33 was formed in a ratio of 1.4:1; combined

yield: 60%; white solid.

1 H NMR (300 MHz, CDCl 3): δ 7.54 (d, J = 8.2 Hz, 2H), 7.12 (d, J = 7.7 Hz, 2H), 6.93 (d,

J = 8.2 Hz, 2H), 6.87 (d, J = 8.4 Hz, 2H), 6.83 (br, 1H), 2.28 (s, 3H), 2.17 (s, 3H).

1 H NMR (300 MHz, CDCl 3): δ 7.56 (d, J = 8.2 Hz, 2H), 7.23 (d, J = 7.8 Hz, 1H), 7.12 (d,

J = 7.7 Hz, 2H), 7.07-6.95 (m, 3H), 6.52 (br, 1H), 2.30 (s, 3H), 1.92 (s, 3H).

209

1H NMR spectra for the mixture of 33 and 34 (Table 3.7, entry 2) 7.62 7.59 7.56 7.15 7.53 7.04 7.00 6.96 6.90 6.84 6.53 2.31 2.29 2.18 1.93 4.90 1.34 5.17 3.46 5.20 1.42 1.00 3.12 4.32 4.29 3.13

210

APPENDIX 18: NMR SPECTRUM OF 22

N-cyclohexyl-4-methyl-benzenesulfonamide 7 22 (Table 3.6, entry 1)

Yield: 40%; pale yellow solid.

1 H NMR (300 MHz, CDCl 3): δ 7.69 (d, J = 8.0 Hz, 2H), 7.22 (d, J = 8.0 Hz, 2H), 4.40 (d,

J = 7.5 Hz, 1H), 3.13 – 2.96 (m, 1H), 2.35 (s, 3H), 1.74 – 1.38 (m, 5H), 1.29 – 0.98 (m,

5H).

1H NMR spectra for 22 (Table 3.6, entry 1) 7.70 7.68 7.23 7.21 4.41 4.39 3.07 3.06 3.04 2.35 1.70 1.56 1.53 1.46 1.43 1.26 1.19 1.14 1.11 1.08 1.05 1.01 2.04 2.21 1.00 0.93 3.45 6.64 6.85

211

APPENDIX 19: NMR SPECTRUM OF 23

N-cyclopentyl-4-methyl-benzenesulfonamide 7 23 (Table 3.6, entry 2)

Yield: 30%; pale yellow solid.

1 H NMR (300 MHz, CDCl 3): δ 7.69 (d, J = 8.1 Hz, 2H), 7.23 (d, J = 7.9 Hz, 2H), 4.46 (d, J = 6.9 Hz, 1H), 3.62 – 3.37 (m, 1H), 2.36 (s, 3H), 1.78 – 1.62 (m, 2H), 1.48 – 1.20 (m, 6H).

1H NMR spectra for 23 (Table 3.6, entry 2) 7.71 7.68 7.24 7.22 4.47 4.44 3.57 3.55 3.52 3.50 3.48 3.46 2.36 1.73 1.69 1.65 1.43 1.42 1.41 1.40 1.38 1.37 1.33 1.31 1.29 1.26 1.24 2.25 2.40 0.98 1.00 3.15 2.37 6.28

212

APPENDIX 20: NMR SPECTRUM OF 19

4-methyl-N-(tetrahydrofuran-2-yl)-benzenesulfonamide 3 19 (Table 3.5)

NHTs O

1 H NMR (300 MHz, CDCl 3) δ 7.83 (d, J = 8.1 Hz, 2H), 7.31 (d, J = 8.1 Hz, 2H), 5.57 (d,

J = 8.9 Hz, 1H), 5.44 – 5.29 (m, 1H), 3.78 – 3.63 (m, 2H), 2.44 (s, 3H), 2.24 – 2.07 (m,

1H), 1.99 – 1.73 (m, 3H).

1H NMR spectra for 19 (Table 3.5) 7.84 7.81 7.32 7.30 5.58 5.56 5.39 5.38 5.37 5.36 5.35 5.34 3.77 3.74 3.73 3.71 3.69 3.66 2.44 2.18 2.12 2.09 1.99 1.97 1.95 1.94 1.92 1.90 1.87 1.85 1.83 1.82 1.80 1.79 1.78 1.76 1.75

with mesitylene as internal standard 2.15 2.14 0.97 0.99 2.00 3.63 1.10 3.21

213

APPENDIX 21: NMR SPECTRA OF 3

(2R,4S)-2,4-diphenyl-1-(toluene-4-sulfonyl)pyrrolidine 8 and (2R,4R)-2,4-diphenyl-1-

(toluene-4-sulfonyl)pyrrolidine 3 (Table 4.1, entry 1)

Based on 1H NMR, 3 was isolated as a cis and trans mixture in 1:1.1 ratio; combined

yield: 55%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.67 (d, J = 8.1 Hz, 2H), O N S 7.47 – 7.21 (m, 10H), 7.16 (d, J = 7.6 Hz, 2H), 4.86 (dd, J O = 9.7, 7.1 Hz, 1H), 4.20 (dd, J = 11.2, 7.6 Hz, 1H), 3.57 (t,

J = 11.3 Hz, 1H), 2.99 (td, J = 12.0, 6.4 Hz, 1H), 2.72 (dt, J = 13.0, 6.6 Hz, 1H), 2.46 (s,

3H), 2.11 – 2.01 (m, 1H).

13 C NMR (75 MHz, CDCl 3): δ 143.4, 142.5, 139.1, 135.8, 129.6, 128.7, 128.5, 127.5,

127.3, 127.2, 127.1, 126.4, 64.5, 55.9, 44.4, 42.1, 21.6.

1 H NMR (300 MHz, CDCl 3): δ 7.76 (d, J = 8.1 Hz, 2H), O N S 7.47 – 7.21 (m, 10H), 7.06 (d, J = 7.4 Hz, 2H), 5.10 (d, J = O 7.9 Hz, 1H), 4.10 – 4.00 (m, 1H), 3.45 – 3.57 (m, 1H), 3.34

(t, J = 9.8 Hz, 1H), 2.48 (s, 3H), 2.27 – 2.11 (m, 2H).

13 C NMR (75 MHz, CDCl 3): δ 143.5, 142.9, 139.6, 134.8, 129.7, 128.6, 128.4, 127.6,

127.2, 127.1, 127.0, 126.1, 63.1, 55.1, 43.7, 41.5, 21.5.

214

1H and 13 C NMR spectra for 3 (cis and trans diastereomer, Table 4.1, entry 1)

215

APPENDIX 22: NMR SPECTRA OF 50

1-(toluene-4-sulfonyl)-(2R,4S)-2,4-di-p-tolyl-pyrrolidine and 1-(toluene-4-sulfonyl)-

(2R,4R)-2,4-di-p-tolyl-pyrrolidine 50 (Table 4.1, entry 2)

Based on 1H NMR, 50 was isolated as a cis and trans mixture in 1:1.2 ratio; combined yield: 70%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.69 (d, J = 8.1 Hz, 2H),

7.39 – 7.07 (m, 8H), 7.05 (d, J = 8.0 Hz, 2H), 4.80 (dd, J O N S = 9.8, 7.0 Hz, 1H), 4.17 (dd, J = 11.1, 7.5 Hz, 1H), 3.53 O (t, J = 11.3 Hz, 2H), 3.03 – 2.86 (m, 1H), 2.67 (dt, J =

12.9, 6.5 Hz, 1H), 2.47 (s, 3H), 2.38 (s, 3H), 2.35 (s, 3H), 2.10 – 2.01 (m, 1H).

13 C NMR (75 MHz, CDCl 3): δ 143.3, 139.6, 136.9, 136.7, 136.1, 135.8, 129.6, 129.3,

129.1, 127.5, 126.9, 126.4, 64.4, 56.0, 44.5, 42.2, 21.5, 21.1, 21.0.

1 H NMR (300 MHz, CDCl 3): δ 7.77 (d, J = 8.1 Hz, 2H),

7.38 – 7.01 (m, 8H), 6.95 (d, J = 7.9 Hz, 2H), 5.05 (d, J O N S = 8.0 Hz, 1H), 4.10 – 3.97 (m, 1H), 3.54 – 3.41 (m, 1H), O 3.29 (t, J = 9.8 Hz, 1H), 2.49 (s, 3H), 2.40 (s, 3H), 2.33

(s, 3H), 2.22 – 2.09 (m, 2H).

13 C NMR (75 MHz, CDCl 3): δ 143.6, 140.1, 136.8, 136.8, 136.6, 134.8, 129.7, 129.3,

129.1, 127.6, 126.9, 126.1, 62.9, 55.2, 43.3, 41.1, 21.6, 21.1, 20.9.

216

1H and 13 C NMR spectra for 50 (cis and trans diastereomer, Table 4.1, entry 2)

217

APPENDIX 23: NMR SPECTRUM OF 51

(2R, 4S)-2,4-bis-(4-chloro-phenyl)-1-(toluene-4-sulfonyl)-pyrrolidine and (2R, 4R)-2,4- bis-(4-chloro-phenyl)-1-(toluene-4-sulfonyl)-pyrrolidine 51 (Table 4.1, entry 3)

Based on 1H NMR, 51 was isolated as a cis and trans mixture in 1:1 ratio; combined yield: 69%; white solid.

1 Cl H NMR (300 MHz, CDCl 3): δ 7.65 (d, J = 8.1 Hz,

2H), 7.39 – 7.20 (m, 8H), 7.07 (d, J = 8.3 Hz, 2H), O N S 4.80 (dd, J = 9.7, 7.0 Hz, 1H), 4.16 (dd, J = 11.8, 7.4 O Hz, 1H), 3.50 (t, J = 11.1 Hz, 1H), 3.06 – 2.88 (m, Cl 1H), 2.67 (dt, J = 13.1, 6.7 Hz, 1H), 2.47 (s, 3H), 1.97 (dd, J = 22.6, 12.5 Hz, 1H).

13 C NMR (75 MHz, CDCl 3): δ 143.7, 140.8, 137.9, 135.5, 133.2, 133.0, 129.7, 128.9,

128.7, 128.3, 127.8, 127.5, 63.8, 55.7, 44.3, 42.0, 21.6.

1 Cl H NMR (300 MHz, CDCl 3): δ 7.72 (d, J = 8.1 Hz,

2H), 7.38 – 7.21 (m, 8H), 6.98 (d, J = 8.3 Hz, 2H), O N S 5.02 (dd, J = 7.5, 2.1 Hz, 1H), 4.06 – 3.98 (m, 1H), O 3.46 – 3.35 (m, 1H), 3.28 (t, J = 9.7 Hz, 1H), 2.48 (s, Cl 3H), 2.13 (d, J = 7.4 Hz, 2H).

13 C NMR (75 MHz, CDCl 3): δ 143.8, 141.3, 137.4, 134.5, 133.1, 132.9, 129.8, 128.8,

128.6, 128.3, 127.6, 127.5, 62.4, 55.0, 43.0, 40.9, 21.5.

218

1H NMR spectra for 51 (cis and trans diastereomer, Table 4.1, entry 3)

219

APPENDIX 24: NMR SPECTRA OF 60

4-phenyl-1-(toluene-4-sulfonyl)-2-p-tolyl-pyrrolidine 60 (Table 4.2, entry 1)

Based on 1H NMR, 60 was isolated as a cis and trans mixture in 1.2:1 ratio; combined yield: 80%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.56 (d, J = 8.1 Hz, 2H),

7.25 – 7.06 (m, 9H), 7.03 (d, J = 7.9 Hz, 2H), 4.67 (dd, J = O N S 9.8, 7.0 Hz, 1H), 4.05 (dd, J = 11.1, 7.7 Hz, 1H), 3.43 (t, J O = 11.3 Hz, 1H), 2.92 – 2.73 (m, 1H), 2.62 – 2.48 (m, 1H),

2.34 (s, 3H), 2.25 (s, 3H), 1.96 – 1.87 (m, 1H).

13 C NMR (75 MHz, CDCl 3): δ 143.3, 139.6, 139.2, 137.0, 135.7, 129.6, 129.2, 128.7,

127.5, 127.1, 127.0, 126.4, 64.4, 55.9, 43.6, 41.5, 21.6, 21.2.

1 H NMR (300 MHz, CDCl 3): δ 7.64 (d, J = 8.1 Hz, 2H),

7.26 – 7.06 (m, 9H), 6.93 (d, J = 6.8 Hz, 2H), 4.93 (d, J = O N S 8.0 Hz, 1H), 3.97 – 3.88 (m, 1H), 3.45 – 3.31 (m, 1H), 3.18 O (t, J = 9.8 Hz, 1H), 2.35 (s, 3H), 2.26 (s, 3H), 2.11 – 1.96

(m, 2H).

13 C NMR (75 MHz, CDCl 3): δ 143.5, 140.0, 139.7, 136.8, 134.7, 129.7, 129.1, 128.6,

127.6, 127.1, 127.0, 126.1, 62.9, 55.1, 44.4, 42.2, 21.6, 21.1.

220

1H and 13 C NMR spectra for 60 (cis and trans diastereomer, Table 4.2, entry 1)

221

APPENDIX 25: NMR SPECTRA OF 62

(2R, 5S)-2,5-diphenyl-3-(toluene-4-sulfonyl)-oxazolidine 9 and (2R, 5R)- 2,5-diphenyl-3-

(toluene-4-sulfonyl)-oxazolidine 62 (Table 4.2, entry 3)

Based on 1H NMR, 62 was isolated as a cis and trans mixture in 1:1.2 ratio; combined yield: 87%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.79 (d, J = 8.4 Hz, 2H),

O 7.62 (m, 2H), 7.42 – 7.24 (m, 10H), 6.35 (s, 1H), 4.54 (dd, O N S O J = 10.1, 5.6 Hz, 1H), 4.18 (dd, J = 11.8, 5.6 Hz, 1H), 3.33

(t, 1H), 2.49 (s, 3H).

13 C NMR (75 MHz, CDCl 3): δ 144.3, 138.7, 136.8, 135.5, 130.0, 129.0, 128.7, 128.6,

128.4, 127.7, 127.0, 126.3, 91.7, 79.7, 53.7, 21.6.

1 H NMR (300 MHz, CDCl 3): δ 7.82 (d, J = 8.3 Hz, 2H),

O 7.69 (d, J = 6.9 Hz, 2H), 7.51 – 7.18 (m, 8H), 6.83 (d, J = O N S O 7.1 Hz, 2H), 6.61 (s, 1H), 4.99 (t, J = 7.6 Hz, 1H), 3.87

(dd, J = 10.4, 7.0 Hz, 1H), 3.39 – 3.31 (m, 1H), 2.54 (s,

3H).

13 C NMR (75 MHz, CDCl 3): δ 144.3, 138.2, 137.7, 133.9, 130.0, 128.8, 128.6, 128.5,

128.4, 128.3, 126.6, 125.9, 91.5, 78.0, 53.6, 21.6.

222

1H and 13 C NMR spectra for 62 (cis and trans diastereomer, Table 4.2, entry 3)

223

APPENDIX 26: NMR SPECTRA OF 63

5-phenyl-3-(toluene-4-sulfonyl)-2-p-tolyl-oxazolidine 63 (Table 4.2, entry 4)

Based on 1H NMR, 63 was isolated as a cis and trans mixture in 1.2:1ratio; combined

yield: 90%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.78 (d, J = 8.2 Hz, 2H),

7.50 (d, J = 8.0 Hz, 2H), 7.41 – 7.19 (m, 9H), 6.30 (s, 1H), O O N S 4.52 (dd, J = 10.1, 5.6 Hz, 1H), 4.16 (dd, J = 11.7, 5.6 Hz, O 1H), 3.38 – 3.26 (m, 1H), 2.49 (s, 3H), 2.41 (s, 3H).

13 C NMR (75 MHz, CDCl 3): δ 144.3, 138.9, 136.9, 135.8, 135.6, 130.0, 129.3, 128.6,

128.6, 127.7, 126.6, 126.3, 91.7, 79.6, 53.7, 21.6, 21.3.

1 H NMR (300 MHz, CDCl 3): δ 7.81 (d, J = 8.3 Hz, 2H),

7.56 (d, J = 8.0 Hz, 2H), 7.42 – 7.20 (m, 7H), 6.82 (d, J = O O N S 7.2 Hz, 2H), 6.57 (s, 1H), 4.98 (t, J = 7.6 Hz, 1H), 3.86 O (dd, J = 10.4, 7.0 Hz, 1H), 3.38 – 3.26 (m, 1H), 2.53 (s,

3H), 2.42 (s, 3H).

13 C NMR (75 MHz, CDCl 3): δ 144.3, 138.6, 137.8, 135.2, 133.9, 130.0, 129.1, 128.5,

128.3, 128.3, 126.9, 125.9, 91.54, 77.9, 53.6, 21.6, 21.2.

224

1H and 13 C NMR spectra for 63 (cis and trans diastereomer, Table 4.2, entry 4)

225

APPENDIX 27: NMR SPECTRA OF 64

2-methyl-2,5-diphenyl-3-(toluene-4-sulfonyl)-oxazolidine 64 (Table 4.2, entry 5)

Based on 1H NMR, 64 was isolated as a cis and trans mixture in 1:1ratio; combined yield: 79%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.83 – 7.70 (m, 4H), 7.41

(m, 3H), 7.32 (m, 5H), 7.23 (m, 2H), 4.95 – 4.83 (m, 1H), O O N S 3.88 (dd, J = 9.0, 6.7 Hz, 1H), 3.50 (t, J = 8.9 Hz, 1H), O 2.48 (s, 3H), 2.07 (s, 3H).

13 C NMR (75 MHz, CDCl 3): δ 143.6, 143.5, 137.9, 137.4, 129.7, 128.6, 128.5, 128.4,

128.22, 127.6, 126.1, 126.0, 99.2, 75.7, 54.9, 26.5, 21.6.

1 H NMR (300 MHz, CDCl 3); δ 7.52 (d, J = 7.3 Hz, 2H),

7.48 – 7.28 (m, 6H), 7.26 – 7.23 (m, 2H), 7.05-6.98 (m, O O N S 4H), 5.43 (dd, J = 10.2, 5.4 Hz, 1H), 4.22 (dd, J = 8.7, 5.4 O Hz, 1H), 3.31 – 3.19 (m, 1H), 2.35 (s, 3H), 2.26 (s, 3H).

226

1H and 13 C NMR spectra for 64 (cis and trans diastereomer, Table 4.2, entry 5)

O NTs

227

APPENDIX 28: NMR SPECTRUM OF 69

2-(N-tosylamino)-1-phenyl-1-ethanol 10 69 (Scheme 4.3)

White solid; hydrolysis product of 64

1 H NMR (300 MHz, CDCl 3): δ 7.75 (d, J = 8.2 Hz, 2H), 7.32 (m, 7H), 5.37 – 5.20 (m,

1H), 4.82 (dd, J = 8.8, 3.4 Hz, 1H), 3.25 (ddd, J = 11.5, 7.7, 3.4 Hz, 1H), 3.04 (ddd, J =

13.1, 8.8, 4.2 Hz, 1H), 2.83 (br, 1H), 2.44 (s, 3H).

228

1H NMR spectra for 69 (hydrolysis product of 64 , Scheme 4.3) 7.76 7.73 7.37 7.34 7.32 7.31 7.30 5.31 5.29 5.27 4.84 4.82 4.81 4.79 3.25 3.08 3.07 3.05 3.04 3.02 3.01 2.99 2.83 2.44 2.20 7.61 1.00 1.07 1.08 1.11 0.99 3.17

229

APPENDIX 29: NMR SPECTRA OF 65 AND 66

3,5-diphenyl-1-(toluene-4-sulfonyl)-2,3-dihydro-1H-pyrrole 11 65 and 2,5-diphenyl-1-

(toluene-4-sulfonyl)-2,3-dihydro-1H-pyrrole 66 (Table 4.2, entry 6)

Based on 1H NMR, a mixture of 65 and 66 was formed in a ratio of 1.4:1; combined

yield: 64%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.67-7.64 (m, 2H), 7.53 (d, J = 8.1 Hz,

2H), 7.44 – 7.42 (m, 3H), 7.24 (d, J = 7.9 Hz, 2H), 7.21 – 7.19 (m, 3H),

NTs 6.90 – 6.87 (m, 2H), 5.46 (d, J = 2.4 Hz, 1H), 4.49 (dd, J = 12.4, 9.7

Hz, 1H), 3.87 (dd, J = 12.4, 8.2 Hz, 1H), 3.77 – 3.66 (m, 1H), 2.48 (s,

3H).

13 C NMR (75 MHz, CDCl 3): δ 145.9, 143.9, 142.4, 133.5, 132.7, 129.5, 129.0, 128.6,

128.1, 127.9, 127.2 126.8, 120.0, 59.8, 46.3, 21.7.

1 H NMR (300 MHz, CDCl 3): δ 7.73 (d, J = 7.5 Hz, 2H), 7.61 (d, J

= 8.2 Hz, 2H), 7.34 (d, J = 7.6 Hz, 2H), 7.31 – 7.26 (m, 6H), 7.10 NTs – 7.03 (m, 2H), 4.86 (s, 1H), 4.35 (dt, J = 8.3, 4.7 Hz, 1H), 4.23 –

4.11 (m, 2H), 2.43 (s, 3H).

13 C NMR (75 MHz, CDCl 3): δ 165.5, 145.3, 142.9, 134.6, 133.0, 130.9, 129.7, 129.2,

129.1, 128.7, 128.3, 127.6, 126.4, 80.6, 67.6, 46.4, 21.7.

230

1H and 13 C NMR spectra for mixuture of 65 and 66 (Table 4.2, entry 6)

NTs NTs

65 66

145.94 145.34 143.91 142.92 142.44 134.45 133.47 133.00 132.70 130.78 129.68 129.53 129.24 129.05 128.99 128.65 128.59 128.32 128.13 127.89 127.47 127.22 126.84 126.36 120.02

231

APPENDIX 30: NMR SPECTRA OF 67

4-methyl-3,5-diphenyl-1-(toluene-4-sulfonyl)-2,3-dihydro-1H-pyrrole 11 67 (Table 4.2, entry 7)

Yield: 68%; sticky solid.

1 H NMR (300 MHz, CDCl 3): δ 7.45 – 7.36 (m, 4H), 7.36 –

O 7.25 (m, 3H), 7.17 (d, J = 8.0 Hz, 2H), 7.08 (d, J = 4.3 Hz, N S O 3H), 6.73 – 6.62 (m, 2H), 4.27 (dd, J = 11.6, 10.6 Hz, 1H),

3.65 (dd, J = 12.1, 7.3 Hz, 1H), 3.56 (d, J = 9.3 Hz, 1H),

2.39 (s, 3H), 1.32 (s, 3H).

13 C NMR (75 MHz, CDCl 3): δ 143.8, 142.2, 140.0, 133.8, 132.7, 130.0, 129.7, 128.8,

128.8, 127.8, 127.0, 126.0, 57.6, 51.9, 21.8, 12.8.

232

1H and 13 C NMR spectra for 67 (Table 4.2, entry 7)

233

APPENDIX 31

Ph Mn X-ray Crystallographic Data for Complex [Tpm Mn(CH 3CN) 3](BF 4)2 (2 )

234

Table 1. Crystal data and structure refinement for 2Mn .

Empirical formula C34 H31 B2F8MnN 9 Formula weight 794.24 Temperature 293(2) K Wavelength 0.71073 Å Crystal system triclinic Space group P1 Unit cell dimensions a = 12.6467(9) Å α= 67.315(1)° b = 12.9873(9) Å β= 70.336(1)° c = 13.4015(9) Å γ = 73.350(1)°

Volume 1881.1(2) Å 3 Z 2 Density (calculated) 1.402 g/cm 3 Absorption coefficient 4.29 cm -1 F(000) 810 Crystal size 0.54 x 0.42 x 0.40 mm θ range for data collection 2.10 to 27.56° Index ranges -15 ≤ h ≤ 16, -15 ≤ k ≤ 16, -17 ≤ l ≤ 17 Reflections collected 13066 Independent reflections 8270 [R(int) = 0.0340] Completeness to θ = 27.56° 95.1 % Max. and min. transmission 0.847 and 0.802 Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 8270 / 74 / 546 Goodness-of-fit on F 2 1.025 Final R indices [I>2 σ(I)] R1 = 0.0546, wR2 = 0.1524 R indices (all data) R1 = 0.0643, wR2 = 0.1642 Largest diff. peak and hole 0.355 and -0.231 e/Å 3

235

Table 2. Atomic coordinates (x 10 4) and equivalent isotropic displacement parameters Mn (Å 2 x 10 3) for 2 . U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. ______x y z U(eq) ______Mn(1) 2074(1) 3991(1) 2022(1) 49(1) N(1) 2254(2) 5440(1) 2512(1) 55(1) N(2) 2155(2) 6496(2) 1753(2) 60(1) N(3) 583(2) 5335(1) 1444(1) 50(1) N(4) 746(2) 6434(1) 979(2) 56(1) N(5) 3041(2) 5008(1) 299(1) 51(1) N(6) 2715(2) 6158(1) -6(1) 54(1) N(7) 2094(2) 2672(2) 1354(2) 63(1) N(8) 3499(2) 2900(2) 2768(2) 62(1) N(9) 933(2) 3055(2) 3593(2) 66(1) C(1) 2566(2) 5560(2) 3319(2) 60(1) C(2) 2663(3) 6691(2) 3050(2) 80(1) C(3) 2394(3) 7254(2) 2060(2) 74(1) C(4) 2783(2) 4597(2) 4300(2) 64(1) C(5) 1966(3) 3937(3) 4986(2) 79(1) C(6) 2225(4) 2997(3) 5886(3) 98(1) C(7) 3261(4) 2738(3) 6090(3) 104(1) C(8) 4063(3) 3411(3) 5438(3) 98(1) C(9) 3829(3) 4337(3) 4544(2) 81(1) C(10) -545(2) 5403(2) 1694(2) 55(1) C(11) -1083(2) 6550(2) 1405(2) 73(1) C(12) -248(2) 7172(2) 962(2) 69(1) C(13) -1055(2) 4376(2) 2222(2) 55(1) C(14) -655(2) 3498(2) 1773(2) 65(1) C(15) -1076(2) 2493(2) 2323(3) 79(1) C(16) -1916(3) 2373(3) 3320(3) 87(1) C(17) -2346(3) 3266(3) 3749(2) 83(1) C(18) -1921(2) 4257(2) 3209(2) 69(1)

236

C(19) 3739(2) 4808(2) -635(2) 54(1) C(20) 3840(2) 5830(2) -1525(2) 67(1) C(21) 3174(2) 6666(2) -1100(2) 65(1) C(22) 4268(2) 3659(2) -681(2) 54(1) C(23) 4765(2) 2847(2) 144(2) 70(1) C(24) 5212(2) 1754(3) 88(3) 85(1) C(25) 5175(3) 1480(3) -785(3) 86(1) C(26) 4699(3) 2277(3) -1619(3) 80(1) C(27) 4249(2) 3367(2) -1572(2) 65(1) C(28) 1849(2) 6717(2) 734(2) 56(1) C(29) 2085(2) 1874(2) 1213(2) 63(1) C(30) 2045(3) 850(3) 1035(3) 94(1) C(31) 4100(2) 2206(2) 3226(2) 62(1) C(32) 4884(3) 1316(3) 3817(3) 96(1) C(33) 590(2) 2339(2) 4342(2) 68(1) C(34) 171(4) 1429(3) 5320(3) 111(1) B(1) 3170(3) 9501(2) 3641(2) 71(1) F(1) 3798(2) 10115(2) 2657(2) 107(1) F(2) 2465(8) 10182(5) 4165(8) 160(4) F(3) 2601(9) 8916(6) 3412(5) 145(4) F(4) 3888(5) 8768(8) 4243(7) 156(5) F(2') 2079(6) 9667(14) 3611(7) 176(8) F(3') 3147(10) 9765(10) 4548(5) 130(5) F(4') 3570(10) 8372(4) 3901(7) 130(5) B(2) 8238(4) 91(3) 1487(3) 104(1) F(5) 7428(3) 548(3) 2208(3) 191(2) F(6) 9146(5) -440(6) 1935(6) 217(3) F(7) 7883(5) -777(3) 1434(4) 139(2) F(8) 8483(7) 804(3) 500(5) 233(5) F(6') 9104(8) 793(10) 1061(9) 126(5) F(7') 8735(14) -919(6) 1832(10) 275(18) F(8') 7908(12) 364(16) 551(9) 282(16) ______

237

Table 3. Selected bond lengths [Å] and angles [°] for 2Mn . ______Mn(1)-N(7) 2.209(2) Mn(1)-N(8) 2.217(2) Mn(1)-N(9) 2.231(2) Mn(1)-N(5) 2.291(2) Mn(1)-N(3) 2.292(2) Mn(1)-N(1) 2.307(2) N(7)-Mn(1)-N(8) 90.27(7) N(7)-Mn(1)-N(9) 86.01(8) N(8)-Mn(1)-N(9) 85.88(8) N(7)-Mn(1)-N(5) 90.81(7) N(8)-Mn(1)-N(5) 101.42(7) N(9)-Mn(1)-N(5) 172.07(7) N(7)-Mn(1)-N(3) 100.64(7) N(8)-Mn(1)-N(3) 168.96(6) N(9)-Mn(1)-N(3) 93.12(7) N(5)-Mn(1)-N(3) 80.32(6) N(7)-Mn(1)-N(1) 172.26(7) N(8)-Mn(1)-N(1) 88.65(7) N(9)-Mn(1)-N(1) 101.55(7) N(5)-Mn(1)-N(1) 81.90(6) N(3)-Mn(1)-N(1) 80.77(6) C(29)-N(7)-Mn(1) 167.2(2) C(31)-N(8)-Mn(1) 167.6(2) C(33)-N(9)-Mn(1) 161.0(2) ______

238

APPENDIX 32

Ph Ni X-ray Crystallographic Data for Complex [Tpm Ni(CH 3CN) 3](BF 4)2 (2 )

239

Ni Table 1. Crystal data and structure refinement for 2 ·CH 3CN .

Empirical formula C36 H34 B2F8N10 Ni Formula weight 839.06 Temperature 293(2) K Wavelength 0.71073 Å Crystal system monoclinic

Space group P2 1/n Unit cell dimensions a = 12.3799(8) Å α= 90° b = 16.6360(10) Å β= 92.677(1)° c = 19.5125(12) Å γ = 90°

Volume 4014.3(4) Å 3 Z 4 Density (calculated) 1.388 g/cm 3 Absorption coefficient 5.61 cm -1 F(000) 1720 Crystal size 0.24 x 0.40 x 0.42 mm θ range for data collection 1.99 to 27.52° Index ranges -15 ≤ h ≤ 16, -21 ≤ k ≤ 19, -24 ≤ l ≤ 25 Reflections collected 27327 Independent reflections 9148 [R(int) = 0.0448] Completeness to θ = 27.52° 99.0 % Max. and min. transmission 0.877 and 0.799 Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 9148 / 10 / 535 Goodness-of-fit on F 2 1.025 Final R indices [I>2 σ(I)] R1 = 0.0545, wR2 = 0.1545 R indices (all data) R1 = 0.0700, wR2 = 0.1703 Largest diff. peak and hole 0.618 and -0.366 e/Å 3

240

Table 2. Atomic coordinates (x 10 4) and equivalent isotropic displacement parameters Ni (Å 2 x 10 3) for 2 ·CH 3CN. U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. ______x y z U(eq) ______Ni(1) 5974(1) 7671(1) 5369(1) 41(1) N(1) 6575(2) 8007(1) 4401(1) 43(1) N(2) 7150(2) 8705(1) 4407(1) 44(1) N(3) 7586(2) 7871(1) 5777(1) 43(1) N(4) 8112(2) 8491(1) 5473(1) 45(1) N(5) 5756(2) 8926(1) 5557(1) 42(1) N(6) 6623(2) 9394(1) 5410(1) 44(1) N(7) 5241(2) 7400(1) 6268(1) 51(1) N(8) 4479(2) 7481(2) 4865(1) 52(1) N(9) 6308(2) 6452(2) 5300(1) 56(1) C(1) 6317(2) 7872(2) 3735(1) 47(1) C(2) 6709(2) 8492(2) 3330(1) 53(1) C(3) 7242(2) 9008(2) 3771(1) 50(1) C(4) 5735(2) 7142(2) 3481(1) 50(1) C(5) 6128(2) 6380(2) 3644(2) 57(1) C(6) 5621(3) 5703(2) 3375(2) 72(1) C(7) 4716(3) 5781(3) 2934(2) 82(1) C(8) 4329(3) 6538(3) 2768(2) 84(1) C(9) 4838(3) 7211(2) 3031(2) 69(1) C(10) 8375(2) 7444(2) 6100(1) 51(1) C(11) 9384(2) 7787(2) 5990(2) 61(1) C(12) 9193(2) 8450(2) 5597(1) 55(1) C(13) 8170(2) 6741(2) 6537(2) 65(1) C(14) 7421(3) 6779(3) 7039(2) 89(1) C(15) 7270(5) 6109(5) 7463(3) 140(3) C(16) 7869(7) 5439(5) 7387(4) 170(4) C(17) 8631(6) 5418(4) 6903(4) 147(3) C(18) 8794(4) 6060(3) 6474(3) 100(1) C(19) 5158(2) 9395(2) 5955(1) 45(1)

241

C(20) 5658(2) 10148(2) 6056(2) 58(1) C(21) 6587(2) 10121(2) 5710(2) 53(1) C(22) 4126(2) 9156(2) 6244(1) 46(1) C(23) 3291(2) 8818(2) 5844(2) 56(1) C(24) 2312(2) 8643(2) 6128(2) 70(1) C(25) 2153(3) 8813(2) 6811(2) 77(1) C(26) 2975(3) 9161(2) 7206(2) 71(1) C(27) 3959(2) 9330(2) 6930(1) 59(1) C(28) 7523(2) 9062(2) 5049(1) 43(1) C(29) 4704(2) 7203(2) 6687(2) 55(1) C(30) 4014(3) 6953(3) 7231(2) 87(1) C(31) 3655(2) 7369(2) 4618(2) 57(1) C(32) 2573(3) 7236(3) 4306(3) 92(1) C(33) 6455(3) 5783(2) 5368(2) 65(1) C(34) 6647(5) 4928(3) 5458(3) 113(2) B(1) 1877(4) 5952(4) 6010(3) 95(2) F(1) 1247(3) 6128(4) 5494(2) 199(2) F(2) 2943(3) 6088(3) 5895(2) 155(2) F(3) 1575(3) 6279(4) 6584(2) 213(3) F(4) 1818(6) 5154(3) 6060(4) 265(3) B(2) 382(3) 9288(3) 4011(2) 75(1) F(5) -499(2) 9679(2) 4305(1) 82(1) F(6) 50(6) 8646(4) 3706(4) 234(4) F(7) 1114(2) 9091(3) 4541(2) 114(1) F(8) 929(3) 9875(2) 3668(2) 117(1) F(5') 119(11) 9403(10) 3322(5) 104(5) F(6') -580(9) 9078(13) 4210(8) 129(6) F(7') 1027(18) 8655(12) 4026(14) 206(12) F(8') 810(30) 9916(13) 4305(15) 340(30) N(10) 10646(6) 6664(5) 3202(4) 161(3) C(35) 10040(7) 6665(5) 3664(6) 152(4) C(36) 9354(7) 6691(7) 4234(6) 217(5)

242

Ni Table 3. Selected bond lengths [Å] and angles [°] for 2 ·CH 3CN. ______Ni(1)-N(7) 2.063(2) Ni(1)-N(9) 2.075(3) Ni(1)-N(8) 2.080(2) Ni(1)-N(1) 2.136(2) Ni(1)-N(3) 2.139(2) Ni(1)-N(5) 2.139(2) N(7)-Ni(1)-N(9) 86.49(10) N(7)-Ni(1)-N(8) 87.21(9) N(9)-Ni(1)-N(8) 89.78(10) N(7)-Ni(1)-N(1) 173.93(8) N(9)-Ni(1)-N(1) 96.85(9) N(8)-Ni(1)-N(1) 87.73(8) N(7)-Ni(1)-N(3) 99.08(8) N(9)-Ni(1)-N(3) 89.50(9) N(8)-Ni(1)-N(3) 173.61(9) N(1)-Ni(1)-N(3) 86.06(8) N(7)-Ni(1)-N(5) 90.18(9) N(9)-Ni(1)-N(5) 172.80(8) N(8)-Ni(1)-N(5) 96.44(9) N(1)-Ni(1)-N(5) 87.05(8) N(3)-Ni(1)-N(5) 84.72(8) C(29)-N(7)-Ni(1) 168.3(2) C(31)-N(8)-Ni(1) 177.2(3) C(33)-N(9)-Ni(1) 169.1(2) ______

243

APPENDIX 33

Me,Me Fe X-ray Crystallographic Data for Complex [Tp Fe(CH 3CN) 3]BF 4 (3 ).

244

Fe Table 1.Crystal data and structure refinement for 3 ·(CH3CN) 0.5 .

Empirical formula C22 H32.5 B2F4FeN 9.5 Formula weight 583.55 Temperature 293(2) K Wavelength 0.71073 Å Crystal system hexagonal Space group R3 (hexagonal setting) Unit cell dimensions a = 11.6034(6) Å α= 90° b = 11.6034(6) Å β= 90° c = 37.890(3) Å γ = 120°

Volume 4418.0(4) Å 3 Z 6 Density (calculated) 1.316 g/cm 3 Absorption coefficient 5.66 cm -1 F(000) 1818 Crystal size 0.14 x 0.40 x 0.42 mm θ range for data collection 2.10 to 27.51° Index ranges -15 ≤ h ≤ 14, -15 ≤ k ≤ 14, -49 ≤ l ≤ 47 Reflections collected 9721 Independent reflections 2248 [R(int) = 0.0378] Completeness to θ = 27.51° 99.2 % Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 2248 / 0 / 115 Goodness-of-fit on F 2 1.052 Final R indices [I>2 σ(I)] R1 = 0.0448, wR2 = 0.1352 R indices (all data) R1 = 0.0474, wR2 = 0.1382 Largest diff. peak and hole 0.563 and -0.319 e/Å 3

245

Table 2. Atomic coordinates (x 10 4) and equivalent isotropic displacement parameters Fe (Å 2 x 10 3) for 3 ·(CH3CN) 0.5 . U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. ______x y z U(eq) ______Fe(1) 10000 10000 863(1) 44(1) N(1) 8405(1) 9754(1) 1198(1) 47(1) N(2) 8697(1) 9897(1) 1550(1) 44(1) N(3) 8586(2) 8356(2) 511(1) 64(1) C(1) 7208(2) 9658(2) 1165(1) 53(1) C(2) 6739(2) 9742(2) 1494(1) 56(1) C(3) 7697(2) 9903(2) 1734(1) 49(1) C(4) 7698(2) 10052(2) 2124(1) 67(1) C(5) 6562(2) 9508(3) 814(1) 75(1) C(6) 7692(2) 7526(2) 376(1) 61(1) C(7) 6501(3) 6460(3) 214(1) 97(1) B(1) 10000 10000 1688(1) 44(1) B(2) 6667 3333 256(2) 87(2) F(1) 6667 3333 -81(2) 241(4) F(2) 7720(2) 4490(2) 363(1) 139(1)

______

246

Fe Table 3. Selected bond lengths [Å] and angles [°] for 3 ·(CH3CN) 0.5 . ______Fe(1)-N(1) 2.1423(14) Fe(1)-N(1)#1 2.1423(14) Fe(1)-N(1)#2 2.1423(14) Fe(1)-N(3) 2.232(2) Fe(1)-N(3)#1 2.232(2) Fe(1)-N(3)#2 2.232(2) N(1)#1-Fe(1)-N(1)#2 88.45(5) N(1)#1-Fe(1)-N(1) 88.45(5) N(1)#2-Fe(1)-N(1) 88.45(5) N(1)-Fe(1)-N(3)#2 179.26(6) N(1)#1-Fe(1)-N(3) 179.26(6) N(1)#2-Fe(1)-N(3)#1 179.26(6) N(1)-Fe(1)-N(3)#1 92.26(6) N(1)#1-Fe(1)-N(3)#2 92.26(6) N(1)#2-Fe(1)-N(3) 92.26(6) N(1)-Fe(1)-N(3) 91.33(6) N(1)#1-Fe(1)-N(3)#1 91.33(6) N(1)#2-Fe(1)-N(3)#2 91.33(6) N(3)-Fe(1)-N(3)#1 87.96(7) N(3)-Fe(1)-N(3)#2 87.96(7) N(3)#1-Fe(1)-N(3)#2 87.96(7) C(6)-N(3)-Fe(1) 166.54(19)

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247

APPENDIX 34

Me,Me Co X-ray Crystallographic Data for Complex [Tp Co(CH 3CN) 3]BF 4 (3 ).

248

Co Table 1. Crystal data and structure refinement for 3 ·(CH3CN) 0.5 .

Empirical formula C22 H32.5 B2CoF 4N9.5 Formula weight 586.63 Temperature 293(2) K Wavelength 0.71073 Å Crystal system hexagonal Space group R3 (hexagonal setting) Unit cell dimensions a = 11.6161(9) Å α= 90° b = 11.6161(9) Å β= 90° c = 37.839(4) Å γ = 120°

Volume 4421.7(7) Å 3 Z 6 Density (calculated) 1.322 g/cm 3 Absorption coefficient 6.36 cm -1 F(000) 1824 Crystal size 0.20 x 0.38 x 0.40 mm θ range for data collection 2.09 to 27.51° Index ranges -14 ≤ h ≤ 13, -15 ≤ k ≤ 15, -48 ≤ l ≤ 45 Reflections collected 10468 Independent reflections 2260 [R(int) = 0.0610] Completeness to θ = 27.51° 99.5 % Max. and min. transmission 0.883 and 0.785 Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 2260 / 0 / 115 Goodness-of-fit on F 2 1.051 Final R indices [I>2 σ(I)] R1 = 0.0470, wR2 = 0.1385 R indices (all data) R1 = 0.0630, wR2 = 0.1478 Largest diff. peak and hole 0.376 and -0.339 e/Å 3

249

Table 2. Atomic coordinates (x 10 4) and equivalent isotropic displacement parameters Co (Å 2 x 10 3) for 3 ·(CH3CN) 0.5 . U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. ______x y z U(eq) ______Co(1) 10000 0 863(1) 47(1) N(1) 8435(2) -224(2) 1195(1) 49(1) N(2) 8707(2) -91(2) 1550(1) 47(1) N(3) 9802(2) 1394(2) 517(1) 64(1) C(1) 7235(2) -322(2) 1157(1) 54(1) C(2) 6751(2) -250(2) 1486(1) 59(1) C(3) 7690(2) -100(2) 1730(1) 51(1) C(4) 7670(3) 32(3) 2120(1) 70(1) C(5) 6610(3) -450(4) 805(1) 78(1) C(6) 9848(3) 2290(3) 383(1) 64(1) C(7) 9948(4) 3470(4) 224(1) 97(1) B(1) 10000 0 1688(1) 46(1) B(2) 6667 3333 237(3) 98(2) F(1) 6667 3333 -93(2) 276(5) F(2) 7727(3) 4481(3) 349(1) 158(1)

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250

Co Table 3. Selected bond lengths [Å] and angles [°] for 3 ·(CH3CN) 0.5 . ______Co(1)-N(1) 2.116(2) Co(1)-N(1)#1 2.116(2) Co(1)-N(1)#2 2.116(2) Co(1)-N(3) 2.182(2) Co(1)-N(3)#1 2.182(2) Co(1)-N(3)#2 2.182(2) N(1)#1-Co(1)-N(1) 88.35(7) N(1)#1-Co(1)-N(1)#2 88.35(7) N(1)-Co(1)-N(1)#2 88.35(7) N(1)-Co(1)-N(3)#1 179.05(8) N(1)#1-Co(1)-N(3)#2 179.05(8) N(1)#2-Co(1)-N(3) 179.05(8) N(1)-Co(1)-N(3)#2 91.37(8) N(1)#2-Co(1)-N(3)#1 91.37(8) N(1)#1-Co(1)-N(3) 91.37(8) N(1)-Co(1)-N(3) 92.55(8) N(1)#1-Co(1)-N(3)#1 92.55(8) N(1)#2-Co(1)-N(3)#2 92.55(8) N(3)#2-Co(1)-N(3)#1 87.75(9) N(3)#2-Co(1)-N(3) 87.75(9) N(3)#1-Co(1)-N(3) 87.75(9) C(6)-N(3)-Co(1) 167.2(2)

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251

APPENDIX 35

Ph,Me Fe X-ray Crystallographic Data for Complex [Tp Fe(CH 3CN)3]BF 4 (4 ).

252

Fe Table 1. Crystal data and structure refinement for 4 ·(CH 3CN) 0.5 .

Empirical formula C37 H38.5 B2F4FeN 9.5 Formula weight 769.74 Temperature 293(2) K Wavelength 0.71073 Å Crystal system triclinic Space group P1 Unit cell dimensions a = 11.5754(9) Å α= 67.126(1)° b = 12.2814(9) Å β= 77.677(1)° c = 15.4083(12) Å γ = 76.193(1)°

Volume 1942.0(3) Å 3 Z 2 Density (calculated) 1.316 g/cm 3 Absorption coefficient 4.47 cm -1 F(000) 798 Crystal size 0.16 x 0.28 x 0.54 mm θ range for data collection 1.88 to 27.60° Index ranges -15 ≤ h ≤ 15, -15 ≤ k ≤ 14, -18 ≤ l ≤ 20 Reflections collected 14016 Independent reflections 8709 [R(int) = 0.0339] Completeness to θ = 27.60° 96.8 % Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 8709 / 22 / 549 Goodness-of-fit on F 2 1.020 Final R indices [I>2 σ(I)] R1 = 0.0496, wR2 = 0.1352 R indices (all data) R1 = 0.0665, wR2 = 0.1484 Largest diff. peak and hole 0.567 and -0.309 e/Å 3

253

Table 2. Atomic coordinates (x 10 4) and equivalent isotropic displacement parameters Fe (Å 2 x 10 3) for 4 ·(CH 3CN) 0.5 . U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. ______x y z U(eq) ______Fe(1) 6906(1) 6212(1) 7038(1) 39(1) N(1) 5379(2) 6736(2) 6289(1) 43(1) N(2) 5649(2) 6694(2) 5387(1) 44(1) N(3) 7824(2) 7476(1) 5795(1) 43(1) N(4) 7564(2) 7539(1) 4945(1) 44(1) N(5) 7503(2) 4827(1) 6398(1) 41(1) N(6) 7661(2) 5328(1) 5424(1) 43(1) N(7) 8430(2) 5403(2) 7864(2) 56(1) N(8) 5939(2) 5049(2) 8313(1) 51(1) N(9) 6419(2) 7584(2) 7703(1) 52(1) C(1) 4189(2) 6811(2) 6515(2) 47(1) C(2) 3695(2) 6821(2) 5767(2) 60(1) C(3) 4633(2) 6743(2) 5068(2) 53(1) C(4) 4609(3) 6721(3) 4107(2) 76(1) C(5) 3555(2) 6875(2) 7442(2) 49(1) C(6) 3033(2) 5921(2) 8112(2) 62(1) C(7) 2475(3) 5972(3) 8983(2) 70(1) C(8) 2402(3) 6977(3) 9196(2) 71(1) C(9) 2896(3) 7932(3) 8538(2) 68(1) C(10) 3477(2) 7874(2) 7671(2) 59(1) C(11) 8333(2) 8442(2) 5588(2) 47(1) C(12) 8395(2) 9106(2) 4623(2) 55(1) C(13) 7908(2) 8518(2) 4232(2) 49(1) C(14) 7754(3) 8816(2) 3222(2) 66(1) C(15) 8777(2) 8701(2) 6308(2) 50(1) C(16) 8419(3) 9828(2) 6383(2) 72(1) C(17) 8837(3) 10068(3) 7061(3) 90(1) C(18) 9617(3) 9221(4) 7641(3) 89(1) C(19) 10002(3) 8144(3) 7542(3) 88(1)

254

C(20) 9576(3) 7880(2) 6886(2) 68(1) C(21) 8206(2) 3743(2) 6621(2) 44(1) C(22) 8837(2) 3570(2) 5795(2) 55(1) C(23) 8474(2) 4580(2) 5054(2) 48(1) C(24) 8862(3) 4893(2) 4005(2) 69(1) C(25) 8211(2) 2859(2) 7601(2) 48(1) C(26) 9267(3) 2373(2) 7994(2) 66(1) C(27) 9285(3) 1459(3) 8876(2) 80(1) C(28) 8268(4) 1014(2) 9356(2) 82(1) C(29) 7219(3) 1483(2) 8980(2) 70(1) C(30) 7171(2) 2413(2) 8105(2) 55(1) C(31) 9198(2) 4929(2) 8293(2) 58(1) C(32) 10200(3) 4336(4) 8837(3) 96(1) C(33) 5476(2) 4393(2) 8959(2) 50(1) C(34) 4873(3) 3546(2) 9781(2) 67(1) C(35) 6227(2) 8323(2) 8003(2) 55(1) C(36) 5951(4) 9284(3) 8389(3) 92(1) B(1) 6956(2) 6578(2) 4904(2) 44(1) B(2) 3030(8) 2128(8) 8905(7) 106(5) F(1) 2593(5) 2630(7) 9560(5) 135(3) F(2) 2197(7) 1626(9) 8775(5) 145(3) F(3) 3303(10) 3032(5) 8120(5) 180(4) F(4) 3986(7) 1305(7) 9219(7) 163(4) B(2') 3127(7) 2027(8) 8700(7) 68(3) F(1') 2717(11) 2051(12) 9575(6) 249(8) F(2') 3098(11) 919(6) 8726(6) 152(4) F(3') 2455(9) 2857(9) 8061(6) 171(5) F(4') 4266(6) 2176(12) 8447(8) 190(5) C(37) 4790(20) -30(20) 4713(14) 95(5) C(38) 5115(14) 174(16) 5493(11) 76(3) N(10) 5360(7) 297(7) 6103(6) 113(2) ______

255

Fe Table 3. Selected bond lengths [Å] and angles [°] for 4 ·(CH3CN) 0.5 . ______Fe(1)-N(1) 2.150(2) Fe(1)-N(8) 2.190(2) Fe(1)-N(5) 2.190(2) Fe(1)-N(3) 2.194(2) Fe(1)-N(9) 2.202(2) Fe(1)-N(7) 2.204(2) N(1)-Fe(1)-N(8) 91.31(7) N(1)-Fe(1)-N(5) 85.57(6) N(8)-Fe(1)-N(5) 93.41(7) N(1)-Fe(1)-N(3) 88.50(7) N(8)-Fe(1)-N(3) 176.24(6) N(5)-Fe(1)-N(3) 90.32(6) N(1)-Fe(1)-N(9) 97.85(7) N(8)-Fe(1)-N(9) 87.48(7) N(5)-Fe(1)-N(9) 176.46(7) N(3)-Fe(1)-N(9) 88.83(7) N(1)-Fe(1)-N(7) 171.55(7) N(8)-Fe(1)-N(7) 83.13(8) N(5)-Fe(1)-N(7) 88.41(7) N(3)-Fe(1)-N(7) 97.46(8) N(9)-Fe(1)-N(7) 88.29(7) C(31)-N(7)-Fe(1) 176.27(2) C(33)-N(8)-Fe(1) 176.11(19) C(35)-N(9)-Fe(1) 175.51(2) ______

256

APPENDIX 36

Me,Me Ni X-ray Crystallographic Data for Complex [Tpm Ni(OH 2)Cl 2] (5 ).

257

Me,Me Ni Table 1. Crystal data and structure refinement for [Tpm Ni(OH 2)Cl 2] (5 ). Empirical formula C16 H24 Cl2 N6 Ni O Formula weight 446.02 Temperature 293(2) K Wavelength 0.71073 Å Crystal system Orthorhombic Space group Pbca Unit cell dimensions a = 15.8781(9) Å α= 90°. b = 13.9478(8) Å β= 90°. c = 35.968(2) Å γ = 90°.

Volume 7965.6(8) Å 3 Z 16 Density (calculated) 1.488 Mg/m 3 Absorption coefficient 1.260 mm -1 F(000) 3712 Crystal size 0.40 x 0.24 x 0.10 mm 3 Theta range for data collection 2.02 to 27.52°. Index ranges -20<=h<=20, -18<=k<=15, -46<=l<=46 Reflections collected 52862 Independent reflections 9092 [R(int) = 0.0593] Completeness to theta = 27.52° 99.1 % Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 9092 / 4 / 497 Goodness-of-fit on F 2 1.025 Final R indices [I>2sigma(I)] R1 = 0.0405, wR2 = 0.0997 R indices (all data) R1 = 0.0574, wR2 = 0.1110 Largest diff. peak and hole 0.620 and -0.436 e.Å -3

258

Table 2. Atomic coordinates ( x 10 4) and equivalent isotropic displacement parameters (Å 2x 10 3) for 5Ni . U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. ______x y z U(eq) ______Ni(1) 5230(1) 9310(1) 1944(1) 31(1) Ni(2) 4685(1) 7710(1) 634(1) 32(1) Cl(1) 6453(1) 9171(1) 1543(1) 42(1) Cl(2) 4487(1) 10336(1) 1512(1) 41(1) Cl(3) 5336(1) 6675(1) 1084(1) 41(1) Cl(4) 3441(1) 7996(1) 1000(1) 43(1) N(1) 5745(1) 10410(1) 2266(1) 37(1) N(2) 5750(1) 10290(1) 2644(1) 36(1) N(3) 4220(1) 9353(1) 2341(1) 35(1) N(4) 4433(1) 9473(2) 2709(1) 39(1) N(5) 5788(1) 8344(1) 2347(1) 35(1) N(6) 5710(1) 8592(1) 2715(1) 36(1) N(7) 4151(1) 6561(1) 335(1) 37(1) N(8) 4282(1) 6532(1) -41(1) 39(1) N(9) 4224(1) 8578(1) 190(1) 36(1) N(10) 4280(1) 8214(1) -164(1) 38(1) N(11) 5755(1) 7536(2) 270(1) 38(1) N(12) 5581(1) 7384(2) -97(1) 40(1) O(1) 4668(1) 8132(1) 1692(1) 37(1) O(2) 5234(1) 8926(1) 875(1) 38(1) C(1) 6183(2) 11211(2) 2204(1) 41(1) C(2) 6466(2) 11588(2) 2543(1) 47(1) C(3) 6192(2) 10996(2) 2819(1) 39(1) C(4) 6314(2) 11595(2) 1823(1) 57(1) C(5) 6315(2) 11028(2) 3230(1) 50(1)

259

C(6) 3390(2) 9250(2) 2341(1) 38(1) C(7) 3069(2) 9282(2) 2707(1) 43(1) C(8) 3744(2) 9412(2) 2935(1) 41(1) C(9) 2901(2) 9099(2) 1990(1) 48(1) C(10) 3790(2) 9488(2) 3350(1) 52(1) C(11) 6088(2) 7453(2) 2350(1) 41(1) C(12) 6188(2) 7127(2) 2716(1) 51(1) C(13) 5942(2) 7861(2) 2944(1) 43(1) C(14) 6276(2) 6918(2) 2003(1) 56(1) C(15) 5942(2) 7926(2) 3359(1) 61(1) C(16) 5311(2) 9493(2) 2809(1) 36(1) C(17) 3731(2) 5757(2) 415(1) 44(1) C(18) 3605(2) 5222(2) 89(1) 53(1) C(19) 3965(2) 5722(2) -199(1) 46(1) C(20) 3466(2) 5522(2) 802(1) 59(1) C(21) 4029(2) 5492(2) -603(1) 66(1) C(22) 3894(2) 9450(2) 147(1) 41(1) C(23) 3744(2) 9633(2) -231(1) 51(1) C(24) 3999(2) 8846(2) -425(1) 42(1) C(25) 3745(2) 10106(2) 466(1) 53(1) C(26) 4017(2) 8657(2) -834(1) 56(1) C(27) 6594(2) 7583(2) 288(1) 41(1) C(28) 6948(2) 7468(2) -67(1) 46(1) C(29) 6292(2) 7352(2) -309(1) 42(1) C(30) 7046(2) 7745(2) 646(1) 60(1) C(31) 6273(2) 7243(2) -722(1) 60(1) C(32) 4716(2) 7315(2) -220(1) 38(1)

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260

Table 3. Selected bond lengths [Å] and angles [°] for 5Ni . ______Ni(1)-O(1) 2.0776(17) Ni(1)-N(1) 2.088(2) Ni(1)-N(3) 2.147(2) Ni(1)-N(5) 2.167(2) Ni(1)-Cl(2) 2.4202(7) Ni(1)-Cl(1) 2.4264(7) Ni(2)-O(2) 2.0932(18) Ni(2)-N(7) 2.108(2) Ni(2)-N(9) 2.136(2) Ni(2)-N(11) 2.159(2) Ni(2)-Cl(3) 2.4004(7) Ni(2)-Cl(4) 2.4077(7) O(1)-Ni(1)-N(1) 172.29(8) O(1)-Ni(1)-N(3) 89.54(8) N(1)-Ni(1)-N(3) 84.50(8) O(1)-Ni(1)-N(5) 88.64(8) N(1)-Ni(1)-N(5) 85.80(8) N(3)-Ni(1)-N(5) 83.06(8) O(1)-Ni(1)-Cl(2) 88.71(6) N(1)-Ni(1)-Cl(2) 96.42(6) N(3)-Ni(1)-Cl(2) 92.64(6) N(5)-Ni(1)-Cl(2) 174.97(6) O(1)-Ni(1)-Cl(1) 91.17(6) N(1)-Ni(1)-Cl(1) 94.28(6) N(3)-Ni(1)-Cl(1) 174.17(6) N(5)-Ni(1)-Cl(1) 91.17(6) Cl(2)-Ni(1)-Cl(1) 93.16(2) O(2)-Ni(2)-N(7) 173.67(8)

261

O(2)-Ni(2)-N(9) 89.58(7) N(7)-Ni(2)-N(9) 84.87(8) O(2)-Ni(2)-N(11) 90.84(8) N(7)-Ni(2)-N(11) 85.49(8) N(9)-Ni(2)-N(11) 83.06(8) O(2)-Ni(2)-Cl(3) 91.71(5) N(7)-Ni(2)-Cl(3) 93.44(6) N(9)-Ni(2)-Cl(3) 173.07(6) N(11)-Ni(2)-Cl(3) 90.11(6) O(2)-Ni(2)-Cl(4) 88.92(6) N(7)-Ni(2)-Cl(4) 94.29(6) N(9)-Ni(2)-Cl(4) 91.93(6) N(11)-Ni(2)-Cl(4) 174.99(6) Cl(3)-Ni(2)-Cl(4) 94.91(3)

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262

APPENDIX 37

Me,Me Ni X-ray Crystallographic Data for Complex [Tpm Ni(OH 2)( m-ClC 6H4CO 2)2] (6 )

263

Ni Table 1. Crystal data and structure refinement for 6 ·CH 2Cl 2·0.5C 6H14 .

Empirical formula C34 H41 Cl 4N6NiO 5 Formula weight 814.24 Temperature 173(2) K Wavelength 0.71073 Å Crystal system Triclinic Space group P-1 Unit cell dimensions a = 10.1691(12) Å α= 98.767(2)°. b = 12.2478(14) Å β= 91.705(2)°. c = 15.6803(18) Å γ = 100.682(2)°.

Volume 1893.3(4) Å 3 Z 2 Density (calculated) 1.428 Mg/m 3 Absorption coefficient 0.843 mm -1 F(000) 846 Crystal size 0.45 x 0.18 x 0.15 mm 3 Theta range for data collection 1.71 to 27.53°. Index ranges -13<=h<=13, -15<=k<=15, 0<=l<=20 Reflections collected 21539 Independent reflections 8523 [R(int) = 0.0309] Completeness to theta = 27.53° 97.7 % Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 8523 / 2 / 436 Goodness-of-fit on F 2 1.084 Final R indices [I>2sigma(I)] R1 = 0.0495, wR2 = 0.1262 R indices (all data) R1 = 0.0649, wR2 = 0.1341 Largest diff. peak and hole 1.840 and -1.886 e.Å -3

264

Table 2. Atomic coordinates ( x 10 4) and equivalent isotropic displacement parameters Ni (Å 2x 10 3) for 6 ·CH 2Cl 2·0.5C 6H14 . U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. ______x y z U(eq) ______Ni(1) 6505(1) 1659(1) 2228(1) 21(1) C(1) 3400(2) 1303(2) 2059(2) 23(1) N(1) 3881(2) 1353(2) 1206(1) 24(1) N(2) 5234(2) 1518(2) 1097(1) 23(1) C(2) 3149(3) 1208(2) 439(2) 27(1) C(3) 4068(3) 1296(2) -179(2) 30(1) C(4) 5342(3) 1493(2) 251(2) 24(1) C(5) 1656(3) 975(3) 365(2) 38(1) C(6) 6665(3) 1679(3) -136(2) 32(1) N(3) 3892(2) 2329(2) 2644(1) 22(1) N(4) 5248(2) 2706(2) 2799(1) 23(1) C(7) 3176(3) 3054(2) 3070(2) 28(1) C(8) 4101(3) 3923(2) 3508(2) 33(1) C(9) 5374(3) 3689(2) 3323(2) 26(1) C(10) 1679(3) 2818(3) 3020(2) 43(1) C(11) 6711(3) 4388(2) 3629(2) 33(1) N(5) 3725(2) 336(2) 2384(1) 24(1) N(6) 5046(2) 257(2) 2494(1) 23(1) C(12) 2875(3) -605(2) 2529(2) 27(1) C(13) 3677(3) -1317(2) 2743(2) 31(1) C(14) 5012(3) -758(2) 2714(2) 28(1) C(15) 1389(3) -725(3) 2464(2) 41(1) C(16) 6258(3) -1177(3) 2902(2) 37(1) O(1) 7708(2) 3048(2) 1901(1) 29(1)

265

O(2) 9413(2) 2366(2) 1279(1) 38(1) C(17) 8807(3) 3147(2) 1537(2) 28(1) C(18) 9418(3) 4313(2) 1384(2) 29(1) C(19) 8691(3) 5176(2) 1512(2) 30(1) C(20) 9247(3) 6221(2) 1322(2) 35(1) Cl(1) 8320(1) 7292(1) 1455(1) 52(1) C(21) 10505(4) 6443(3) 1023(2) 47(1) C(22) 11232(3) 5591(3) 908(2) 50(1) C(23) 10699(3) 4532(3) 1079(2) 41(1) O(3) 7510(2) 1857(2) 3421(1) 29(1) O(4) 9032(2) 746(2) 3191(1) 36(1) C(24) 8515(3) 1466(2) 3647(2) 28(1) C(25) 9139(3) 1919(2) 4544(2) 30(1) C(26) 8733(4) 2806(3) 5049(2) 50(1) C(27) 9338(4) 3216(3) 5870(2) 55(1) Cl(2) 8757(2) 4285(1) 6530(1) 143(1) C(28) 10355(4) 2775(3) 6187(2) 51(1) C(29) 10737(4) 1890(5) 5693(2) 77(2) C(30) 10140(4) 1462(4) 4878(2) 60(1) O(5) 7760(2) 620(2) 1677(1) 28(1) C(31) 5212(4) 1722(3) 4897(2) 56(1) Cl(3) 3622(1) 884(1) 4605(1) 67(1) Cl(4) 5107(2) 3021(1) 5519(1) 76(1) ______

266

Ni Table 3. Selected bond lengths [Å] and angles [°] for 6 ·CH 2Cl 2·0.5C 6H14 . ______Ni(1)-O(1) 2.0461(18) Ni(1)-O(3) 2.0639(18) Ni(1)-O(5) 2.0795(19) Ni(1)-N(4) 2.099(2) Ni(1)-N(2) 2.129(2) Ni(1)-N(6) 2.153(2) O(1)-Ni(1)-O(3) 92.63(8) O(1)-Ni(1)-O(5) 91.33(8) O(3)-Ni(1)-O(5) 91.15(7) O(1)-Ni(1)-N(4) 88.83(8) O(3)-Ni(1)-N(4) 88.16(8) O(5)-Ni(1)-N(4) 179.30(8) O(1)-Ni(1)-N(2) 90.36(8) O(3)-Ni(1)-N(2) 171.78(8) O(5)-Ni(1)-N(2) 96.44(8) N(4)-Ni(1)-N(2) 84.25(8) O(1)-Ni(1)-N(6) 173.19(8) O(3)-Ni(1)-N(6) 92.75(8) O(5)-Ni(1)-N(6) 92.72(8) N(4)-Ni(1)-N(6) 87.18(8) N(2)-Ni(1)-N(6) 83.75(8) ______

267

Ni Table 4. Hydrogen bonds for 6 ·CH 2Cl 2·0.5C 6H14 [Å and °]. ______D-H...A d(D-H) d(H...A) d(D...A) <(DHA) ______O(5)-H(5D)...O(2) 0.834(18) 1.82(2) 2.632(3) 163(4) O(5)-H(5E)...O(4) 0.824(18) 1.84(2) 2.638(3) 164(4) ______

268

APPENDIX 38

Me,Me Ni X-ray Crystallographic Data for Complex [(Tpm )2Ni][Ni(NHTs) 4] ( 7 )

269

Ni Table 1. Crystal data and structure refinement for 7 ·2CH 3CN. Empirical formula C64 H82 N18 Ni 2O8S4 Formula weight 1477.14 Temperature 123(2) K Wavelength 0.71073 Å Crystal system Monoclinic Space group P2(1)/n Unit cell dimensions a = 11.9729(12) Å α= 90°. b = 18.5906(19) Å β= 101.162(1)°. c = 15.7359(16) Å γ = 90°.

Volume 3436.3(6) Å 3 Z 2 Density (calculated) 1.428 Mg/m 3 Absorption coefficient 0.737 mm -1 F(000) 1552 Crystal size 0.50 x 0.50 x 0.15 mm 3 Theta range for data collection 1.71 to 27.49°. Index ranges -15<=h<=15, 0<=k<=24, 0<=l<=20 Reflections collected 40943 Independent reflections 7871 [R(int) = 0.0319] Completeness to theta = 27.49° 99.7 % Refinement method Full-matrix least-squares on F 2 Data / restraints / parameters 7871 / 1 / 451 Goodness-of-fit on F 2 1.066 Final R indices [I>2sigma(I)] R1 = 0.0315, wR2 = 0.0790 R indices (all data) R1 = 0.0431, wR2 = 0.0873 Largest diff. peak and hole 0.520 and -0.370 e.Å -3

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Table 2. Atomic coordinates ( x 10 4) and equivalent isotropic displacement parameters Ni (Å 2x 10 3) for 7 ·2CH 3CN. U(eq) is defined as one third of the trace of the orthogonalized U ij tensor. ______x y z U(eq) ______Ni(1) 5000 5000 10000 14(1) N(1) 4872(1) 4766(1) 8104(1) 17(1) N(2) 5622(1) 4964(1) 8840(1) 17(1) N(3) 3537(1) 4062(1) 8687(1) 16(1) N(4) 4095(1) 4058(1) 9538(1) 16(1) N(5) 3212(1) 5315(1) 8440(1) 17(1) N(6) 3588(1) 5542(1) 9278(1) 16(1) C(1) 5380(2) 4718(1) 7402(1) 20(1) C(2) 6505(2) 4886(1) 7703(1) 22(1) C(3) 6619(2) 5037(1) 8592(1) 19(1) C(4) 4756(2) 4524(1) 6517(1) 30(1) C(5) 7670(2) 5261(1) 9210(1) 23(1) C(6) 2877(1) 3464(1) 8481(1) 18(1) C(7) 3018(2) 3063(1) 9229(1) 20(1) C(8) 3779(1) 3445(1) 9865(1) 17(1) C(9) 2179(2) 3331(1) 7599(1) 24(1) C(10) 4218(2) 3228(1) 10786(1) 21(1) C(11) 2386(2) 5750(1) 7997(1) 20(1) C(12) 2213(2) 6272(1) 8577(1) 23(1) C(13) 2969(2) 6128(1) 9359(1) 19(1) C(14) 1877(2) 5648(1) 7062(1) 28(1) C(15) 3108(2) 6542(1) 10187(1) 23(1) C(16) 3685(1) 4668(1) 8142(1) 16(1) Ni(2) 0 5000 5000 15(1)

271

N(7) 979(1) 5811(1) 4942(1) 19(1) S(1) 1959(1) 5961(1) 4428(1) 17(1) O(1) 2453(1) 6668(1) 4638(1) 24(1) O(2) 2761(1) 5364(1) 4534(1) 24(1) C(17) 1358(2) 6001(1) 3302(1) 19(1) C(18) 706(2) 5430(1) 2908(1) 24(1) C(19) 248(2) 5459(1) 2029(1) 29(1) C(20) 429(2) 6053(1) 1531(1) 31(1) C(21) 1084(2) 6616(1) 1936(1) 32(1) C(22) 1547(2) 6597(1) 2817(1) 28(1) C(23) -81(2) 6091(2) 578(1) 44(1) N(8) -1344(1) 5583(1) 4707(1) 20(1) S(2) -1593(1) 6405(1) 4838(1) 17(1) O(3) -821(1) 6846(1) 4458(1) 22(1) O(4) -2800(1) 6554(1) 4558(1) 24(1) C(24) -1282(2) 6626(1) 5964(1) 18(1) C(25) -394(2) 7089(1) 6287(1) 22(1) C(26) -208(2) 7300(1) 7150(1) 26(1) C(27) -895(2) 7055(1) 7704(1) 28(1) C(28) -1768(2) 6576(1) 7377(1) 29(1) C(29) -1964(2) 6359(1) 6517(1) 25(1) C(30) -700(2) 7307(2) 8635(1) 42(1) N(9) 4513(2) 6490(2) 7082(2) 64(1) C(31) 4758(2) 6496(1) 6427(2) 37(1) C(32) 5062(2) 6483(2) 5582(2) 58(1) ______

272

Ni Table 3. Selected bond lengths [Å] and angles [°] for 7 ·2CH 3CN. ______Ni(1)-N(2) 2.1017(15) Ni(1)-N(2)#1 2.1017(15) Ni(1)-N(6)#1 2.1022(14) Ni(1)-N(6) 2.1022(14) Ni(1)-N(4)#1 2.1129(14) Ni(1)-N(4) 2.1129(14) Ni(2)-N(8)#2 1.9205(15) Ni(2)-N(8) 1.9205(15) Ni(2)-N(7) 1.9222(15) Ni(2)-N(7)#2 1.9222(15) N(2)-Ni(1)-N(2)#1 180.000(1) N(2)-Ni(1)-N(6)#1 94.06(6) N(2)#1-Ni(1)-N(6)#1 85.94(6) N(2)-Ni(1)-N(6) 85.94(6) N(2)#1-Ni(1)-N(6) 94.06(6) N(6)#1-Ni(1)-N(6) 180.0 N(2)-Ni(1)-N(4)#1 94.63(5) N(2)#1-Ni(1)-N(4)#1 85.37(5) N(6)#1-Ni(1)-N(4)#1 84.65(5) N(6)-Ni(1)-N(4)#1 95.35(5) N(2)-Ni(1)-N(4) 85.37(5) N(2)#1-Ni(1)-N(4) 94.63(5) N(6)#1-Ni(1)-N(4) 95.35(5) N(6)-Ni(1)-N(4) 84.65(5) N(4)#1-Ni(1)-N(4) 180.0 N(8)#2-Ni(2)-N(8) 180.00(9) N(8)#2-Ni(2)-N(7) 87.91(6) N(8)-Ni(2)-N(7) 92.09(6) N(8)#2-Ni(2)-N(7)#2 92.09(6) N(8)-Ni(2)-N(7)#2 87.91(6) N(7)-Ni(2)-N(7)#2 180.0 ______

273

Ni Table 4. Hydrogen bonds for 7 ·2CH 3CN [Å and °]. ______D-H...A d(D-H) d(H...A) d(D...A) <(DHA) ______N(7)-H(7B)...O(3) 0.811(17) 2.130(18) 2.881(2) 154(2) N(8)-H(8A)...O(2)#2 0.811(17) 2.112(18) 2.863(2) 154(2) ______Symmetry transformations used to generate equivalent atoms: #1 -x+1,-y+1,-z+2 #2 -x,-y+1,-z+1

274

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