Organometallic Bonding And Reactivity: Fundamental Studies (topics In Organometallic Chemistry)

The making and breaking of carbon-metal bonds is fundamental to all the processes of organometallic chemistry and metal mediated homogeneous or heterogeneous catalysis. The ever expanding scope of highly specific stoichiometric and catalytic transformations or organic substrates involving metals requires a thorough physical and theoretical understanding of fundamental principles of organometallic structure and reactivity. Diffraction experiments form the basis of tailoring the molecular architecture of organometallic compounds for specific functions. Mass spectrometric techniques possess the power to provide direct information on the energetics of transient species generated in the gas-phase. Computational chemistry with ab initio or density functional methods make a reliable numerical assessment of structures and (relative) energies increasingly feasible. Embedding methods, combining quantum chemistry with force field of semiempirical MO treatments, quantum dynamic studies and the computational modelling of solvent effects extend the utility of the basic methods. This volume in the series Topics in Organometallic Chemistry presents a survey by renowned experts of important experimental and theoretical developments to elucidate basic aspects of bonding, energetics, reaction mechanisms, molecular geometries and solid-state structures of organometallic compounds. Written by authors with frontier research expertise in their fields, both experimental and quantum chemical techniques, methodologies, results and interpretations are detailed in a manner suitable for the non-specialist, who seeks state-of-the-art information in the respective field. Organometallic Bonding and Reactivity 3 Volume Editors 5 Editorial Board 5 Preface 6 Contents 14 Gas-Phase Organometallic Chemistry 15 Introduction 17 Experimental Methods 18 Atomic Metal and Metal Complex Ion Sources 18 Electron Ionization 19 Laser Vaporization and Glow Discharge 19 Surface Ionization 20 Multiphoton Ionization 20 High-Pressure Sources 20 Mass Spectrometric Methods 21 ICR Mass Spectrometry 21 Ion Beam Mass Spectrometry 21 Thermochemistry of Metal–Carbon Bonds 23 Methods of Analysis 24 Reactions 24 Data Analysis 25 Covalent Metal–Carbon Bonds 26 Cations 26 Bis-Ligated Cations 29 Neutrals 30 Dative Metal–Carbon Bonds 31 Ethene 31 Benzene 32 Alkanes 33 Mechanisms for Alkane Activation 33 Methane 34 Early First Row Transition Metal Ions 35 Late First Row Transition Metal Ions 37 Second and Third Row Transition Metal Ions 39 Ethane 41 Propane 45 Late First Row Transition Metal Ions 46 Early First and Second Row Transition Metal Ions 48 Effect of Ancillary Ligands 49 Effect of an Oxo Ligand 51 Reaction of CoO+ with Methane 52 Reaction of FeO+ with Methane 54 Reaction of Other Transition Metal Oxide Cations with Methane 54 Conclusions 54 References 55 Static and Dynamic Structures of Organometallic Molecules and Crystals 60 Introduction 61 Static and Dynamic Structures of Organometallic Molecules in the Solid State 63 Single Crystal X-ray Diffraction: Some Limitations 65 Dynamical Processes at Molecular Level 66 The Timescale in Diffraction Experiments 66 Atomic Displacements 68 Empirical Estimate of Reorientational Barriers 69 Organometallic Crystal Isomerization, Phase Transitions and Polymorphism 70 Crystal Polymorphism 72 Crystals Formed by Structural Isomers 73 Pseudo-Polymorphism of Electronic Isomers 74 Pseudo-Polymorphism Arising from Disorder 75 Crystal Transformations and Dynamics 75 Perspectives of an Organometallic Solid State and Materials Chemistry 77 References 79 Theoretical Treatment of Organometallic Reaction Mechanisms and Catalysis 82 Introduction 83 Methods 84 Qualitative Molecular Orbital Theory 84 Nonempirical Methods 86 Standard Ab Initio Methods 87 Density Functional Theory Methods 89 QM/MM Methods 90 QM/MD Methods 90 Selected Examples 91 Olefin Polymerization Using Metallocene-Based Transition-Metal Catalysts 91 Olefin Polymerization Using Late Transition-Metal Complexes as Catalysts 108 Olefin Hydroformylation and the Wacker Process: Influence of the Solvent Effects 111 Conclusion and Perspectives 115 References 116 A Critical Assessment of Density Functional Theory with Regard to Applications in Organometallic Chemistry 121 Introduction 123 Significant Problems and the Historical Role of Density Functional Theory 123 Perspectives and Priorities 125 Basics of Density Functional Theory – A Descriptive Presentation 126 Density Functional Theory of Closed-Shell Systems: Non-Spin-Polarized Theory 126 Density Functionals and Model Wave Functions 126 The Kohn-Sham Procedure 129 Effective Potentials 133 Kohn-Sham Eigenvalues 135 Extension to Open-Shell Systems 138 Spin Density Functional Theory 138 Spatial Symmetry Aspects 139 Physical Constraints on Functionals from Properties of Electron Holes 142 Exchange and Correlation Holes; Functionals 142 Approximate Functionals 145 Local and Gradient-Corrected Approximate Functionals 146 Hybrid Approximate Functionals 149 Selected Applications 152 Calibration and Validation 152 Organometallics – Broad View 157 Organometallics – Case Study of Transition-Metal-Catalyzed Oxygen Transfer Reactions 163 Olefin Dihydroxylation with OsO4/H2O2 163 Olefin Epoxidation with CH3ReO3/H2O2 166 Acknowlgements 170 References 170 Hybrid Quantum Mechanics/Molecular Mechanics Methods in Transition Metal Chemistry 176 Introduction 177 Hybrid QM/MM Methods 179 General Overview 179 One-Step QM/MM Methods: Combined MO+MM Method 181 Multistep QM/MM Methods: The IMOMM Method 182 Checklist of Technical Features 184 Applications 184 Structural Studies 185 Olefin Polymerization Via Homogeneous Catalysis 188 Asymmetric Dihydroxylation of Olefins 191 Agostic Complexes 195 Bioinorganic Complexes 197 Conclusions and Future Perspectives 199 Acknowledgement 199 References 200 Author index Volumes 1-4 203 General The making and breaking of carbon-metal bonds is fundamental to all the p- cesses of organometallic chemistry and moreover plays a significant role in - mogeneous as well as heterogeneous catalysis. This rather blunt statement - phasises the extent to which a proper understanding of the structure, energetics and reactivity of C-M bonds is at the core of the discipline. In order to accept it, a proper definition of the terms involved is required. Quite simply we define the metal-carbon bond in its broadest sense to embrace carbon linked to transiti- metals, lanthanides and actinides, and main group metals. We do not dist- guish between formally covalent single or multiple bonding on the one hand and q-bonding on the other. In the studies to be described in the following chapters, the emphasis will be on transition metal complexes and insofar as the fun- mentals come under scrutiny, simple metal alkyls or related species (metal al- nyl, alkynyl, aryl, or allyl) will play an emphatic part. The central role of metal alkyls and their congeners and especially the role of their metal carbon linkage in homogeneous catalysis may be appreciated by considering some key reaction steps leading to their formation or breakdown. There follows a few prominent examples of transition metal mediated stoichiometric or catalytic processes: - In homogeneous hydrogenation of double bonds, the stepwise reaction of an q2-coordinated alkene with dihydrogen gives first an alkyl metal hydride, and then the decoordinated alkane by elimination.

Written by experts and pioneers in the field, the volume addresses state-of-the-art theoretical and experimental methodologies applicable to fundamental problems of structure and reactivity of organometallic compounds. The principles of ab initio and density functional theory, as well as integrated force field/quantum chemistry approaches are outlined, with particular emphasis on their applicability to transition metal organometallic molecules and their reactions. Specific case studies, spanning a range from static structural aspects to molecular structure dynamics, reaction mechanisms and catalytic cycles illustrate the power of modern quantum chemistry for organometallics. Experimental properties of organometallic systems, derived from gas phase organometallic chemistry as well as solid state structural chemistry provide deep and complementary insights into the fundamentals of the chemistry of the metal-carbon bond.

Gas-Phase Organometallic Chemistry....Pages 1-45 Static and Dynamic Structures of Organometallic Molecules and Crystals....Pages 47-68 Theoretical Treatment of Organometallic Reaction Mechanisms and Catalysis....Pages 69-107 A Critical Assessment of Density Functional Theory with Regard to Applications in Organometallic Chemistry....Pages 109-163 Hybrid Quantum Mechanics/Molecular Mechanics Methods in Transition Metal Chemistry....Pages 165-191 This volume addresses theoretical and experimental methodologies applicable to the structure and reactivity of organometallic compounds. The principles of ab initio and density functional theory, as well as integrated force field-quantum chemistry approaches are outlined.