Reactivity Studies of Catalytically Relevant Palladium Model Complexes by Ansis Maleckis

223 Pages·2014·4.61 MB·English

Reactivity Studies of Catalytically Relevant Palladium Model
Complexes

by

Ansis Maleckis

A dissertation submitted in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy
(Chemistry)
in The University of Michigan
2014

Doctoral Committee:

Professor Melanie S. Sanford, Chair
Professor Mark Banaszak Holl
Professor Erdogan Gulari
Professor John P. Wolfe
© Ansis Maleckis

2014
Acknowledgements

I would like to thank my advisor, Professor Melanie Sanford for having me as a
member of her research group. I thank you for your ideas, suggestions and unceasing
enthusiasm for research and science. You taught me how to explore, write and present
chemistry. I am extremely grateful to you also for your infinite understanding and
tolerance towards my unruly and idiosyncratic personality.
I thank my dissertation committee members, Professors John P. Wolfe, Mark
Banaszak Holl and Erdogan Gulari for their invaluable time and advice. I must thank the
department staff for all the help they have provided. DRs. Eugenio Alvarado and Chris
Kojiro for assistance with NMR experiments, DRs Jim Windak and Paul Lennon for
Mass spectrometry analyses and Dr Jeff W. Kampf for X-ray structures.

ii
Table of Contents

Acknowledgments......................................................................................................ii
List of Tables .............................................................................................................vi
List of Schemes ..........................................................................................................vii
List of Figures ............................................................................................................xii
Abstract ......................................................................................................................xv

Chapter 1
Introduction ................................................................................................................1

1.1 Reactivity Studies of Well Defined Palladium(IV) Centers ............................1
1.2 Studies towards Nickel and Palladium Catalyzed Trifluoromethylation .........6
1.3 References ........................................................................................................9

Chapter 2
Design and Synthesis of Palladium(IV) Model Complexes Supported by Facial
Tridentate Ligands .....................................................................................................11

iii
2.1 Introduction ..........................................................................................................11
2.2 Synthesis of Supporting fac-L X Ligands ...........................................................11
2
2.3 Preparation of (fac-L X)PdII(Aryl)(CF ) Complexes ..........................................13
2 3
2.4 Preparation and Reactivity of (fac-L X)PdIV(Aryl)(CF )(Hal) Complexes .........17
2 3
2.5 Conclusions ..........................................................................................................29
2.6 Experimental Section ...........................................................................................29
2.7 References ............................................................................................................59

Chapter 3
Investigation of C–H Activation at Palladium(IV) ....................................................61

3.1 Introduction ..........................................................................................................61
3.2 Synthesis of the [(Py CH)PdIV(biphenyl)Cl ]X Model System ...........................64
3 2
3.3 Reactivity of the Model Complexes ....................................................................68
3.4 Proposed Mechanism of C–H Activation at Palladium(IV) ................................71
3.5 Ligand Substitution at Palladium(IV) ..................................................................73
3.6 Rotation about the PdIV–C Bond .....................................................................78
Aryl
3.7 Configurational Isomerization at PdIV via Berry Pseudorotation ........................80
3.8 Acetate Assisted C–H Cleavage at Palladium(IV) ..............................................82
3.9 Regioselectivity of C–H Activation at Palladium(IV) .........................................85
3.10 Conclusions ........................................................................................................87
3.11 Experimental Section .........................................................................................88
3.12 References ..........................................................................................................140
iv
Chapter 4
Synthesis of Trifluoromethyl Complexes Using TFAA as CF Source ....................142
3

4.1 Introduction ..........................................................................................................142
4.2 Decarbonylative Synthesis of Nickel Trifluoromethyl Complexes .....................146
4.3 Decarbonylative Synthesis of PdII Trifluoromethyl Complexes ..........................150
4.4 Reactivity of the Perfluoroalkyl Nickel and Palladium Complexes ....................156
4.5 Conclusions ..........................................................................................................157
4.6 Experimental Section ...........................................................................................158
4.7 References ............................................................................................................179

Chapter 5
Catalytic Cycle of Trifluoromethylation with TFAA as a CF Source ......................181
3

5.1 Introduction ..........................................................................................................181
5.2 Oxidative Addition of TFA Esters to (RuPhos) Pd0 ............................................184
n
5.3 Decarbonylative Decomposition of (RuPhos)Pd(COR)(OCOR).......................186
f f
5.4 Transmetallation and Reductive Elimination.......................................................189
5.5 Conclusions ..........................................................................................................191
5.6 Experimental Section ...........................................................................................191
5.7 References ............................................................................................................205

v
List of Tables

Chapter 2
Design and Synthesis of Palladium(IV) Model Complexes Supported by Facial Tridentate
Ligands

Table 2.1 Preparation of (fac-L X)PdIV(Aryl)(CF )(Cl) complexes ................................. 19
2 3
Table 2.2 Reactions of (dpaa)PdII(Aryl)(CF ) with NFTPT ............................................. 20
3

Chapter 3
Investigation of C–H Activation at Palladium(IV)

Table 3.1 Spin-lattice relaxation times (T ) for complexes 7, 8 and 9.............................. 66
1
Table 3.2 MS data of [(Py CH)PdIV([1,1'-biphenyl]-2,2’-diyl)(Cl)]+ (12) ..................... 137
3
Table 3.3 MS data for intramolecular KIE determination .............................................. 137

vi
List of Schemes

Chapter 1
Introduction

Scheme 1.1 Diastereoselective Csp3-H iodination.............................................................. 2
Scheme 1.2 Acetoxylation and arylation of unactivated Csp3-H bonds ............................. 2
Scheme 1.3 Synthesis of TP and BiPy supported PdIV complexes ..................................... 3
Scheme 1.4 Formation of PdIV via oxidative addition of aryliodide to PdII ....................... 4
Scheme 1.5 Oxidative PdIV mediated fluorination of arylboronic acids ............................ 4
Scheme 1.6 Directed PdIV mediated C–H chlorination ...................................................... 5
Scheme 1.7 Directed PdIV mediated C–H sulfonylation ..................................................... 5
Scheme 1.8 Catalytic cycle for proposed trifluoromethylation reaction ............................ 8

Chapter 2
Design and Synthesis of Palladium(IV) Model Complexes Supported by Facial Tridentate
Ligands

Scheme 2.1 Synthesis of fac-L X ligands 2 and 3 ............................................................ 13
2
Scheme 2.2 Synthesis of fac-L X ligand 4 ....................................................................... 13
2
Scheme 2.3 Preparation of cis-(4-Mepy) Pd(4-MeC H )(CF ) ........................................ 14
2 6 4 3
vii
Scheme 2.4 Preparation of (Tp)PdII(4-MeC H )(CF )...................................................... 15
6 4 3
Scheme 2.5 Preparation of (L X)PdII(4-MeC H )(CF ) complexes ................................. 15
2 6 4 3
Scheme 2.6 Preparation of (Tp)PdIV(Aryl)(CF )(Cl) ........................................................ 18
3
Scheme 2.7 Reactivity of (Tp)PdIV(Aryl)(CF )(Cl) .......................................................... 18
3
Scheme 2.8 Reaction of (dpsa)PdIV(Aryl)(CF )(F) with TMSOTf .................................. 23
3
Scheme 2.9 Synthesis of (dpph)PdIV(Aryl)(CF )(Cl) ....................................................... 24
3
Scheme 2.10 Reactivity of of (dpph)PdIV(Aryl)(CF )(Cl) with L-type ligands ............... 26
3
Scheme 2.11 Reactivity of of (dpph)PdIV(Aryl)(CF )(Cl) with X-type ligands ............... 27
3
Scheme 2.12 Preparation of (dpph)PdIV(biphe)(Cl) ......................................................... 28

Chapter 3
Investigation of C–H Activation at Palladium(IV)

Scheme 3.1 para-Selective arylation of monosubstituted arenes ...................................... 61
Scheme 3.2 Oxidative dimerization of 2-arylpyridines .................................................... 62
Scheme 3.3 Carboamination of alkenes ............................................................................ 62
Scheme 3.4 Intramolecular C–H activation at a PdIV ....................................................... 63
Scheme 3.5 Preparation of [(Py CH)PdIV([1,1'-biphenyl]-2-yl)(Cl) ][X] Complexes ..... 64
3 2
Scheme 3.6 Binding of chloride counterion to [(Py CH)PdIV([1,1'-biphenyl]-2-yl)(Cl) ] 67
3 2
Scheme 3.7 Thermal decomposition of [(Py CH)PdIV([1,1'-biphenyl]-2-yl)(Cl) ][Cl].... 68
3 2
Scheme 3.8 Reactions of [(Py CH)PdIV([1,1'-biphenyl]-2-yl)(Cl) ][Cl] with bases ........ 69
3 2
Scheme 3.9 Concerted metallation-deprotonation (CMD) mechanism ............................ 69
Scheme 3.10 Acetate promoted C–H activation at PdIV ................................................... 70
viii
Scheme 3.11 Proposed mechanism for acetate-assisted C–H activation at PdIV .............. 72
Scheme 3.12 Chloride-to-acetate ligand substitution at PdIV ........................................... 73
Scheme 3.13 Detection of [(Py CH)PdIV([1,1'-biphenyl]-2-yl)(Cl)(OAc)]+ by NMR ..... 74
3
Scheme 3.14 Preparation of PdIV bromide and azide complexes ..................................... 74
Scheme 3.15 Preparation of [(Py CH)PdIV([1,1'-biphenyl]-2,2’-diyl)(Br)][TfO] ............ 76
3
Scheme 3.16 Reaction of [(Py CCH )PdIV(biphenyl-2,2’-diyl)(Br)][TfO] with AgOAc 77
3 3
Scheme 3.17 Chloride-to-bromide ligand exchange rate at PdIV ...................................... 78
Scheme 3.18 Rotation about the PdIV–C bond ............................................................. 79
Aryl
Scheme 3.19 Isomerization of [(Py CH)PdIV([1,1'-biphenyl]-2-yl)(Br) ][IBr ] ............... 81
3 2 2
Scheme 3.20 Determination of intramolecular KIE ......................................................... 83
Scheme 3.21 Determination of intermolecular KIE ......................................................... 84
Scheme 3.22 Regioselective acetate-assisted C–H activation at PdIV .............................. 85
Scheme 3.23 C–O bond forming reductive elimination process at PdIV center ................ 86
Scheme 3.24 General procedure for the synthesis of iodobiphenyls ................................ 90
Scheme 3.25 Synthesis of 2,6-dideutero-4-(t-butyl)-5'-fluoro-2'-iodobiphenyl (S14) ..... 94
Scheme 3.26 Synthesis of 2-deutero-2'-iodo-1,1'-biphenyl (S15) .................................... 97
Scheme 3.27 Equilibrium between conformers of (Py CH)PdII(biphen-2-yl)(I) .............. 99
3

Chapter 4
Synthesis of Trifluoromethyl Complexes Using TFAA as CF Source
3

Scheme 4.1. Swarts reaction ........................................................................................... 142
Scheme 4.2. McLoughlin-Thrower reaction ................................................................... 143
ix