RHODIUM AND IRON COMPLEXES AND TRANSITION STATES: A COMPUTATIONAL, SPECTROSCOPIC AND ELECTROCHEMICAL STUDY. M.M. CONRADIE RHODIUM AND IRON COMPLEXES AND TRANSITION STATES: A COMPUTATIONAL, SPECTROSCOPIC AND ELECTROCHEMICAL STUDY. A thesis submitted to meet the requirements for the degree of Philosophiae Doctor in the Department of Chemistry Faculty of Natural and Agricultural Sciences at the University of the Free State by Marrigje Marianne Conradie promotor Prof. J. Conradie March 2010 I will be with you. I will not fail you nor forsake you. Joshua 1:5 Acknowledgments My further gratitude hereby expressed to: Prof. Jeanet Conradie, my mother and promoter, thank you for your devotion, support and late night discussions. Mr. Hans Koorts, my grandfather, who read this thesis for language and grammar editing. Family and friends, especially my sister Susan and my friend Liesel, for motivation and support. Prof. Jannie Swarts and colleagues, for valuable inputs and discussions. The Chemistry Department and the University of the Free State, for available facilities. Prof. Abhik Gosh and the bioinorganic chemistry group, for research opportunities and teaching me valuable computational skills. CTCC and the University of Tromsø, for available facilities. The National Research Foundation, for financial support. TABLE OF CONTENTS Table of contents Chapter 1 Introduction and aim of study ...............................................................................1 1.1 Introduction ...................................................................................................1 1.2 Aim of study ..................................................................................................7 Chapter 2 Survey of literature and fundamental aspects .....................................................9 2.1 Computational chemistry ..............................................................................9 2.1.1 Introduction ........................................................................................9 2.1.2 Basic Quantum Chemistry ...............................................................12 2.1.3 Density Functional Theory (DFT) ...................................................13 2.1.4 Amsterdam Density Functional (ADF) ............................................14 2.1.5 Gaussian03 .......................................................................................15 2.1.6 Exchange-and-correlation (XC) Functional .....................................15 2.1.7 Database ...........................................................................................17 2.2 Fundamental Concepts ................................................................................19 2.2.1 Basic Point Group Theory ................................................................19 2.2.2 Transition Metal Coordination .........................................................23 2.2.3 Crystal Field Theory (CFT) .............................................................25 2.2.4 Molecular Orbital (MO) Theory ......................................................30 2.2.5 Ligand Field Theory (LFT) ..............................................................33 2.2.6 Spin Crossover (SCO) ......................................................................33 2.2.7 Potential Energy Surface (PES) .......................................................35 2.3 Electrochemistry .........................................................................................39 2.3.1 Introduction ......................................................................................39 2.3.2 Cyclic Voltammetry (CV) ................................................................40 2.3.3 Spectroelectrochemistry (SEC) ........................................................45 2.4 Rhodium complexes ....................................................................................47 2.4.1 Square planar Rh(I) and octahedral Rh(III) chemistry ....................47 – 2.4.2 The Monsanto Process: [Rh(CO) 2I2] + CH 3I ..................................61 2.4.3 [Rh( β-diketonato)(CO)(PPh 3)] + CH 3I ............................................69 2.4.4 [Rh(acac)(P(OPh) 3)2] + CH 3I ...........................................................74 2.5 Iron complexes ............................................................................................77 2.5.1 [Fe( β-diketonato) 3] ...........................................................................77 2.5.2 [Fe(salen)(CH 3)2(COCH 3)2(py) 2] .....................................................82 2.5.3 [Fe(porphyrin)(Ar)] ..........................................................................85 TABLE OF CONTENTS Chapter 3 Results and discussion ..........................................................................................95 3.1 Rhodium complexes ....................................................................................95 3.1.1 Introduction ......................................................................................95 3.1.2 [Rh(acac)(CO)(PPh 3)] + CH 3I .........................................................97 3.1.3 [Rh( β-diketonato)(CO)(PPh 3)] + CH 3I ..........................................120 3.1.4 [Rh(acac)(P(OPh) 3)2] + CH 3I .........................................................129 3.1.5 Crystal structure of [Rh(bth)(CO) 2] ...............................................144 3.2 Iron complexes ..........................................................................................152 3.2.1 [Fe( β-diketonato) 3] .........................................................................152 3.2.2 [Fe(salen)(CH 3)2(COCH 3)2(py) 2] ...................................................168 3.2.3 [Fe(porphyrin)(Ar)] ........................................................................179 Chapter 4 Experimental .......................................................................................................193 4.1 Materials ....................................................................................................193 4.2 Techniques and apparatus .........................................................................193 4.2.1 Melting point (m.p.) determination ................................................193 4.2.2 Analysis ..........................................................................................193 4.2.3 Spectroscopic measurements .........................................................193 4.2.4 Spectrophotometric measurements ................................................194 4.2.5 Electrochemistry ............................................................................194 4.3 Synthesis ...................................................................................................195 4.3.1 β-diketones .....................................................................................195 4.3.2 Rhodium complexes .......................................................................195 4.3.3 [Fe( β-diketonato) 3] complexes { 1}-{10 } ......................................195 4.4 Crystallography .........................................................................................202 4.4.1 Structure determination of [Rh(bth)(CO) 2] ....................................202 4.5 Computational ...........................................................................................203 4.5.1 Resources .......................................................................................203 4.5.2 Rhodium complexes .......................................................................206 4.5.3 Iron complexes ...............................................................................208 Chapter 5 Concluding remarks and future perspectives ..................................................211 5.1 Concluding remarks ..................................................................................211 5.2 Future perspectives ...................................................................................216 TABLE OF CONTENTS Appendix A Infrared spectrophotometry (IR) .....................................................................................A-1 Ultraviolet spectrophotometry (UV) ...............................................................................A-6 Mass spectrometry (MS) ...............................................................................................A-11 Cyclic voltammetry (CV) ..............................................................................................A-16 Appendix B Crystallography: supporting information .........................................................................CD Appendix C Computational: supporting information ..........................................................................CD Abstract and keywords Opsomming en sleutelwoorde CHAPTER 1 Introduction and aim of study 1 1.1 Introduction. The formation and breaking of metal-carbon bonds have become an important and versatile tool in synthetic organic chemistry. 1 Transition metal assisted reactions used for the manufacture of organic compounds on an industrial scale include the oxidation, hydrogenation, hydroformylation, isomerization and polymerization of alkenes, diene cyclooligomerization and alcohol carbonylation. Other reactions, such as the asymmetric hydrogenation of prochiral alkenes, the activation of C-H bonds for hydrogen/deuterium exchange, the reduction of ketones by hydrosilation and the decarbonylation of aldehydes are also catalyzed by complexes of transition metals.