UNIVERSITY OF CALIFORNIA, SAN DIEGO Structural and electronic studies of complexes relevant to the electrocatalyic reduction of carbon dioxide. A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Chemistry by Eric Edward Benson Committee in charge: Professor Clifford P. Kubiak, Chair Professor Andrew G. Dickson Professor Joshua S. Figueroa Professor Arnold L. Rheingold Professor Michael J. Tauber 2012 Copyright Eric Edward Benson, 2012 All rights reserved Signature Page The dissertation of Eric Edward Benson is approved, and it is acceptable in quality and form for publication on microfilm and electronically. Chair University of California, San Diego 2012 iii DEDICATION to my family iv EPIGRAPH Epigraph The further one goes, the less one knows. –Lao Tzu v TABLE OF CONTENTS Table of Contents Signature Page ............................................................................................................. iii Epigraph ........................................................................................................................ v Table of Contents ......................................................................................................... vi List of Figures .............................................................................................................. ix Lists of Schemes .......................................................................................................... xv List of Tables .............................................................................................................. xvi Acknowledgments ...................................................................................................... xxi Vita ............................................................................................................................ xxvi Abstract of the Dissertation ................................................................................... xxvii Chapter 1 Electrocatalytic and homogenous approaches to conversion of CO 2 to liquid fuels. ................................................................................................................ 1 1.1 Introduction ........................................................................................................ 1 1.1.1 The challenge of CO2 reduction, thermodynamic considerations. ............ 2 1.1.2 The challenge of CO2 reduction, kinetic considerations. ........................... 2 1.2 Tutorial on electrocatalysis ................................................................................. 3 1.3 A review of CO2 reduction catalysts to date ...................................................... 5 1.3.1 Metal complexes with macrocyclic ligands. .............................................. 7 1.3.2 Metal complexes with bipyridine ligands. ................................................ 12 1.3.3 CO2 reduction by transition metal phosphine complexes. ....................... 14 1.4 Lessons from nature ......................................................................................... 22 1.4.1 Ni-Fe-S. .................................................................................................... 23 1.4.2 Mo-S-Cu. .................................................................................................. 25 1.5 De Novo synthetic catalysts. ............................................................................. 27 1.6 Conclusions and Future Directions .................................................................. 31 1.7 References ........................................................................................................ 35 Chapter 2 Synthesis and characterization of 6,6’-(2,4,6-triisopropylphenyl)-2,2’- bipyridine (tripbipy) and its complexes of the late first row transition metals. ......... 39 2.1 Introduction ...................................................................................................... 39 2.2 Results and discussion ...................................................................................... 41 2.2.1 X-ray Crystallography .............................................................................. 42 2.2.2 Electronic Spectra ..................................................................................... 49 2.2.3 Magnetic Studies: ..................................................................................... 52 2.2.4 Electrochemistry ....................................................................................... 54 2.2.5 EPR ........................................................................................................... 55 2.3 Conclusions ...................................................................................................... 55 2.4 Experimental ..................................................................................................... 56 2.5 References ........................................................................................................ 60 2.6 Appendix .......................................................................................................... 63 vi Chapter 3 Stabilization of intermediates through the use of a bulky bipyridine, 6,6’-(2,4,6-triisopropylphenyl)-2,2’-bipyridine, in the reduction of CO 2 by rhenium polypyridyl complexes. .......................................................................................... 102 3.1 Introduction .................................................................................................... 102 3.2 Results and discussion .................................................................................... 104 3.2.1 Synthesis and FTIR spectroscopy .......................................................... 104 3.2.2 Electrochemistry ..................................................................................... 106 3.2.3 X-Ray crystallography ............................................................................ 107 3.3 Conclusions .................................................................................................... 111 3.4 Experimental ................................................................................................... 112 3.5 References ...................................................................................................... 115 3.6 Appendix ........................................................................................................ 118 Chapter 4 Structural investigations into the deactivation pathway of the CO 2 reduction electrocatalyst Re(bpy)(CO) 3Cl ......................................................................... 141 4.1 Introduction .................................................................................................... 141 4.2 Results and discussion .................................................................................... 143 4.3 Conclusions .................................................................................................... 149 4.4 Experimental ................................................................................................... 150 4.5 References ...................................................................................................... 153 4.6 Appendix ........................................................................................................ 156 - Chapter 5 FTIR and XRD characterization of M(bipy-R)(CO) 3 anions: electronic and structural properties of compounds relevant to the electrocatalytic reduction of CO 2 ........................................................................................................................................... 193 5.1 Introduction .................................................................................................... 193 5.2 Results and discussion .................................................................................... 195 5.2.1 Synthesis and Infrared Spectroscopy ...................................................... 195 5.2.2 Crystallography of rhenium anions ........................................................ 197 5.2.3 DFT of rhenium anions .......................................................................... 201 5.2.4 Re(bipy-CF3)(CO)3Cl ............................................................................ 205 5.2.5 Mn(bipy-tBu)(CO)3Cl ............................................................................ 206 5.3 Conclusions .................................................................................................... 209 5.4 Experimental ................................................................................................... 210 5.5 References ...................................................................................................... 216 5.6 Appendix ........................................................................................................ 219 Chapter 6 EXAFS and XANES of rhenium compounds relevant to the electrochemical reduction of CO 2......................................................................................... 300 6.1 Introduction .................................................................................................... 300 6.2 Results and discussion .................................................................................... 304 6.3 Conclusions .................................................................................................... 309 6.4 Experimental ..................................................................................................