Luận án tiến sĩ: Tổng hợp, cấu trúc và phản ứng phức imido cobalt

SYNTHESIS, STRUCTURE, AND REACTIVITY OF TERMINAL COBALT IMIDO COMPLEXES by Daniel Travis Shay A dissertation submitted to the Faculty of the University of Delaware in partial fulfillment of the requirements for the degree Doctor of Philosophy in Chemistry and Biochemistry. Fall 2006 Copyright 2006 Daniel Travis Shay All Rights Reserved UMI Number: 3247713 UMI Microform 3247713 Copyright 2007 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.

ProQuest Information and Learning Company 300 North Zeeb Road P. Box 1346 Ann Arbor, MI 48106-1346 SYNTHESIS, STRUCTURE, AND REACTIVITY OF TERMINAL COBALT IMIDO COMPLEXES by Daniel Travis Shay Approved:_________________________________________________ Charles G. Chair of the Department of Chemistry and Biochemistry Approved:_________________________________________________ Thomas M. Dean of the College of Arts and Sciences Approved:_________________________________________________ Daniel Rich, Ph.

Provost I certify that I have read this dissertation and in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Professor in Charge of dissertation I certify that I have read this dissertation and in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Member of dissertation committee I certify that I have read this dissertation and in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Member of dissertation committee I certify that I have read this dissertation and in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy.

Signed:___________________________________________________________ Roger Grey, Ph. Member of dissertation committee Acknowledgements I would first like to thank my advisor Klaus H. Theopold for giving me the opportunity to work in his laboratory on such an interesting research project. He has been a wonderful mentor offering me guidance throughout the past five years.

I am proud to hold the degree of Doctor of Philosophy in Chemistry from his research group at the University of Delaware. I would also like to thank all the students and professors in the Chemistry Department at the University of Delaware who have helped me during my time at the University. I would like to thank the Theopold group (both past and present) for their help and input for my projects. Also, I would like to thank both Dr.

Riordan and Dr. Fox and their respective groups for allowing me to use both their time and their student’s time for helpful discussions, and of course their lab supplies. I would like to thank the departmental staff for helping me keep the lab running smoothly. Our electronic and glass shop have always responded very quickly when their services were required.

Last but not least, I would like to thank my wife Ni Yan who has given me the support and encouragement to complete my Ph. She has pushed me each time I thought the road was long and for that I am grateful. I would also like to thank myself for sticking with it and seeing it to the end. IV Dedicated to my loving wife Ni Yan V Table of Contents List of Tables--------------------------------------------------------------------------- IX List of Figures-------------------------------------------------------------------------- XI List of Schemes------------------------------------------------------------------------- XII Abstract----------------------------------------------------------------------------------- XIV Introduction------------------------------------------------------------------------------ 1 Synthesis, Structure, Reactivity of Terminal Imido Complexes-Results and Discussion Synthesis and Structure-------------------------------------------------------- 14 Spectroscopic Characterization----------------------------------------------- 36 Reactivity------------------------------------------------------------------------ 48 Conclusion----------------------------------------------------------------------- 87 Experimental Section----------------------------------------------------------- 88 General Techniques---------------------------------------------------- 88 Synthesis of TptBu,MeCoNAd------------------------------------------ 89 Synthesis of TptBu,MeCoNtBu------------------------------------------ 89 Synthesis of TptBu,MeCoNMe------------------------------------------ 90 Synthesis of TptBu,MeCoNEt-------------------------------------------- 91 Synthesis of BptBu,Me(Me-pz-CMe2CH2N(Ad)H)Co --------------- 92 Synthesis of BptBu,Me(Me-pz-CMe2CH2N(Ad)H)CoI -------------- 93 Synthesis of BptBu,Me(Me-pz-CMe2CH2N(tBu)H)Co --------------- 93 Synthesis of TptBu,MeCo(Lut)BARF----------------------------------- 94 Synthesis of TptBu,MeK-d9---------------------------------------------- 95 VI Synthesis of TptBu,MeCo(N3)------------------------------------------- 97 Reaction of TptBu,MeCoNAd with HCl--------------------------------- 98 Reaction of TptBu,MeCoNAd with H2O------------------------------- 98 Reaction of TptBu,MeCoNAd with CO-------------------------------- 98 Reaction of TptBu,MeCoNtBu with CO-------------------------------- 99 Reaction of TptBu,MeCoLutBARF with O2--------------------------- 99 Adamantyl Aziridine---------------------------------------------------- 100 Adamantyl Piperidine---------------------------------------------------- 100 Methyl Azide------------------------------------------------------------- 101 Azo Adamantane--------------------------------------------------------- 102 Kinetic Isotope Effect Measurements--------------------------------- 102 Crystal Structure Determinations--------------------------------------- 103 Appendix A Figure A1.1 Field dependence of magnetic susceptibility of 1---- 104 Crystal Data and Structure Refinement for TptBu,MeCoNAd-1/2 C5H12 (1)----------------------------------------- 105 TptBu,MeCoNtBu-1/3 C5H12 (2)---------------------------------------- 106 TptBu,MeCoNMe (3)------------------------------------------------------ 107 TptBu,MeCoNEt (4)-------------------------------------------------------- 108 TptBu,MeCoLutBARF-1/2 C5H12 (5)------------------------------------- 109 BptBu,Me(Me-pz-CMe2CH2N(Ad)H)Co (6)----------------------------- 110 BptBu,Me(Me-pz-CMe2CH2N(Ad)H)CoI (7)---------------------------- 111 BptBu,Me(Me-pz-CMe2CH2N(tBu)H)Co (8)----------------------------- 112 VII Table A1.

9 Temperature (oC) vs Chemical Shift (ppm) for 1 ----- 113 Table A1.10 Temperature (oC) vs Chemical Shift (ppm) for 1d27 -- 114 References------------------------------------------------------------------------------------- 115 VIII List of Tables Table 1.1 Interatomic distances in Å for TptBu,MeCoNAd, (1)-------------------------- 16 Table 1.2 Interatomic angles in degree for TptBu,MeCoNAd, (1)----------------------- 17 Table 1.3 Interatomic distances in Å for TptBu,MeCoNtBu, (2)------------------------- 22 Table 1.4 Interatomic angles in degree for TptBu,MeCoNtBu, (2)----------------------- 23 Table 1.5 Interatomic distances in Å for TptBu,MeCoNMe, (3)-------------------------- 28 Table 1.6 Interatomic angles in degree for TptBu,MeCoNMe, (3)----------------------- 29 Table 1.7 Interatomic distances in Å for TptBu,MeCoNEt, (4)--------------------------- 32 Table 1.8 Interatomic angles in degree for TptBu,MeCoNEt, (4)------------------------- 33 Table 1.9 List of chemical shifts for TptBu,MeCoNAd and TptBu,MeCo15Nad --------- 46 Table 1.10 Interatomic distances in Å for [TptBu,MeCo(Lut)][BARF], (5)------------ 54 Table 1.11 Interatomic angles in degree for [TptBu,MeCo(Lut)][BARF], (5)---------- 55 Table 1.12 Interatomic distances in Å for BptBu,Me(Me-pz-CMe2CH2N(Ad)H)Co, (6)-------------------------------------------------------------------------------------- 62 Table 1.13 Interatomic bond angles in degree for BptBu,Me(Me-pz-CMe2CH2N(Ad)H)Co, (6)-------------------------------------------------------------------------------------- 63 Table 1.14 Interatomic distances in Å for BptBu,Me(Me-pz-CMe2CH2N(Ad)H)CoI, (7)-------------------------------------------------------------------------------------- 69 Table 1.15 Interatomic bond angles in degree for BptBu,Me(Me-pz-CMe2CH2N(Ad)H)CoI, (7)------------------------------------- 70 Table 1.16 Interatomic distances in Å for BptBu,Me(Me-pz-CMe2CH2N(tBu)H)Co, (8)-------------------------------------------------------------------------------------- 74 Table 1.17 Interatomic angles in degree for BptBu,Me(Me-pz-CMe2CH2N(Ad)H)Co, IX (8)------------------------------------------------------------------------------------ 75 Table 1.18 Rate Constants (S-1) and isotope effects for the interconversion of 1 to 6--------------------------------------------------------------------------------- 85 Table A1.1 Crystal data and structure refinement for TptBu,MeCoNAd⋅1/2 C5H12, 1 105 Table A1.2 Crystal data and structure refinement for TptBu,MeCoNtBu⋅1/3 C5H12, 2 106 Table A1.3 Crystal data and structure refinement for TptBu,MeCoNMe, 3 ------------ 107 Table A1.4 Crystal data and structure refinement for TptBu,MeCoNEt, 4 ------------ 108 Table A1.5 Crystal data and structure refinement for [TptBu,MeCoLut][BARF] ⋅1/2 C5H12, 5------------------------------------------------------------------------ 109 Table A1.6 Crystal data and structure refinement for BptBu,Me(Me-pz- CMe2CH2N(Ad)H)Co, 6 -------------------------------------------------------- 110 Table A1.7 Crystal data and structure refinement for BptBu,Me(Me-pz- CMe2CH2N(Ad)H)CoI, 7 --------------------------------------------------------- 111 Table A1.8 Crystal data and structure refinement for BptBu,Me(Me-pz- CMe2CH2N(tBu)H)Co, 8 --------------------------------------------------------- 112 Table A1.10 Temperature (oC) vs Chemical Shift (ppm) for 1d27 ------------------- 114 X List of Figures Figure 1.1 Simplified bonding description of terminal imido complexes--------- 1 Figure 1.2 Molecular orbital diagrams of an octahedral metal imido complex depicting the π bonding interaction---------------------------------------------------------------- 3 Figure 1.3 Examples of terminal cobalt (III) imido complexes-------------------- 4 Figure 1.4 The multiple step synthesis of a terminal nickel II imido species---- 7 Figure 1.5 Reaction of an electrophile with an iridium t-butyl imido complex- 9 Figure 1.6 Nucleophilic attack of triphenyl phosphene with a chromium aryl imido complex resulting in ligand transfer-------------------------------------------------- 9 Figure 1.7 Copper catalyzed aziridination of olefins------------------------------- 10 Figure 1.8 One of the more common ligands employed for the catalytic aziridination of olefins-------------------------------------------------------------------------------------- 10 Figure 1.9 Mechanistic picture for the aziridination of olefins-------------------- 11 Figure 1.10 C-H activation of an inferred cobalt imido complex-------------------- 13 Figure 1.11 Molecular structure of TptBu,MeCoNAd, complex 1-------------------- 15 Figure 1.12 Molecular structure of TptBu,MeCoNtBu, complex 2-------------------- 21 Figure 1.13 Molecular structure of TptBu,MeCoNMe, complex 3-------------------- 27 Figure 1.14 Molecular structure of TptBu,MeCoNEt, complex 4---------------------- 31 Figure 1.15 1H NMR spectrum of TptBu,MeCoNAd, 1, in benzene C6D6 at 295K--- 38 Figure 1.16 d orbital splitting pattern of degenerate metal d orbitals in C3V symmetry- 39 Figure 1.17 Magnetic susceptibility and moment as a function of temperature of complex 1 ---------------------------------------------------------------------------- 42 Figure 1.18 Magnetic susceptibility and moment as a function of temperature of XI complex 1 after Hgo----------------------------------------------------------------- 43 Figure 1.19 Variable temperature 1H NMR analysis of 1 in C6D6--------------------- 45 Figure 1.201H NMR of 1:1 mixture of TptBu,MeCo14NAd and TptBu,MeCo15NAd in benzene C6D6 at 295K----------------------------------------------------------- 47 Figure 1.21A The molecular structure and of [TptBu,MeCo(Lut)][BARF], 5----------- 52 Figure 1.21B The molecular structure and of [TptBu,MeCo(Lut)][BARF], 5----------- 53 Figure 1.22 The molecular structure of BptBu,Me(Me-pz-CMe2CH2N(Ad)H)Co, 6--- 61 Figure 1.23 The molecular structure of BptBu,Me(Me-pz-CMe2CH2N(Ad)H)CoI, 7-- 68 Figure 1.24 Molecular structure of BptBu,Me(Me-pz-CMe2CH2N(tBu)H)Co, (8)--- 73 Figure 1.25 Interconversion of 1 to 6 at 335.26 Erying Analysis of TptBu,MeCoNAd from 40-90oC-------------------------- 81 Figure A1.1 Field dependence of magnetic susceptibility of 1 ------------------------- 104 XII List of Schemes Scheme 1.1 Possible organic transformation products of TptBu,MeCoNAd with ethylene 60 Scheme 1.2 Synthesis of pinacolone d3--------------------------------------------------------- 82 XIII Synthesis, Structure, and Reactivity of TptBu,MeCoNR (TptBu,Me = hydrotris(3-tBu-5- Me- pyrazolyl)borate) (R = Me, Et, tBu, Ad) Abstract The synthesis and structural characterization of imido ligated cobalt complexes that employ the sterically hindered hydrotris(3-tBu-5-Me-pyrazolyl)borate ligand, i., TptBu,MeCoNR (R = Me, Et, tBu, Ad) have been accomplished. These terminal imido complexes possess relatively short Co-N bond distances in the range of 1.67 Å, indicating a multiple bond to the metal. Reactivity studies have been undertaken with a variety of substrate ranging from protonation using acids such as HCl and lutidinium- BARF (BARF = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) to ligand transfer of the imido fragment to carbon monoxide. Kinetic studies of the thermal decomposition of TptBu,MeCoNAd which undergoes C-H activation of the Tp ligand yielding BptBu,Me(Me-pz-CMe2CH2N(Ad)H)Co, have been closely monitored by 1H NMR spectroscopy.

Determination of the rate of C-H insertion of the imido ligand of TptBu,MeCoNAd at a variety of temperatures led to the generation of an Erying Plot which showed curvature. Kinetic isotope measurements were also conducted showing a temperature dependent kinetic isotope effect indicating that breaking of the C-H bond was involved in the rate determining step. XIV Introduction Stable terminal imido complexes of the late first row transition metals are rare, presumably due to a lack of empty d orbitals available to accept π donation from the NR2- ligand.1 The imido moiety is a strong π-donor ligand, and as such is generally found coordinated to early metals in high oxidation states with d0-d2 configurations.2 Transition metal imido complexes have been postulated as the key intermediates in NR group transfer reactions.3 They have also gained interest because of their role as the catalytically active species in olefin aziridination.4 Metal imido complexes can be categorized into two different classes.5 The first category is linear, i., when an imido complex exhibits a M-N-R bond angle in the range of 160o to 180o.5 The second category is considered to be bent; here the M-N-R bond angle is between 130o to 150o.5,6 Valence bond theory suggests the principal bonding modes consist of one σ and one to two π bonds depending on the interaction of the nitrogen’s lone pair electrons with the metal.1 represents a simplified view of the two different bonding modes of the terminal imido ligand with a transition metal.8 M N R M N R Bonding Mode A Bonding Mode B Figure 1.1: Simplified bonding description of terminal imido complexes. Structure A depicts the linear fashion with the N atom to be considered sp hybridized while structure B shows the bent bonding mode and considers the N atom to be sp2 hybridized.

In this simplified bonding description of the imido ligand, the interaction of 1 the N atom’s lone pair electrons with that of the metal d orbitals determines a linear or bent structure. If empty d orbitals are available for bonding, one can image more interaction of the N atom’s electrons representing a more linear M-N-R bond. In more electron rich compounds bending of the M-N-R bond can occur and the lone pair electrons will be more localized on the nitrogen (bonding mode B). However, bending of the M-N-R bond can occur in complexes with electron deficient metal centers.

One such example is Os(NtBu)4. The Os-N-C bonds are bent with an angle of 156.9 Despite the interaction of the nitrogen’s electrons it is common to represent the metal to ligand bond as M=NR. This allows for a more simplified assignment of the metal’s oxidation state with the imido ligand acting as a di anionic 4 e- donor.