ORBITAL INTERACTIONS IN CHEMISTRY

Transcription

1 ORBITAL INTERACTIONS IN CHEMISTRY THOMAS A. ALBRIGHT Department of Chemistry University of Houston JEREMY K. BURDETT Department of Chemistry The University of Chicago MYUNG-HWAN WHANGBO Department of Chemistry North Carolina State University A Wiley-Interscience Publication JOHN WILEY & SONS New York Chichester Brisbane Toronto Singapore

2 Contents 1. ATOMIC AND MOLECULAR ORBITALS 1.1. Introduction, Atomic Orbitals, Molecular Orbitals, 5 2. CONCEPTS OF BONDING AND ORBITAL INTERACTION 2.1. Orbital Interaction Energy, 12 A. Degenerate Interaction, 13 B. Nondegenerate Interaction, Molecular Orbital Coefficients, 18 A. Degenerate Interaction, 18 B. Nondegenerate Interaction, Electron Density Distribution, PERTURBATIONAL MOLECULAR ORBITAL THEORY 3.1. Introduction, Nondegenerate Perturbation, 28 A. Intramolecular Perturbation, 29 B. Intermolecular Perturbation, Degenerate Perturbation, 34 A. Intramolecular Perturbation, 34 B. Intermolecular Perturbation, The Linear H 3 Molecule, SYMMETRY CONSIDERATIONS 4.1. Introduction, Groups, Symmetry-Adapted Wavefunctions, Degeneracies, Direct Products, 48

3 CONTENTS 4.6. Symmetry Properties and Integrals, The Noncrossing Rule, Principles of Orbital Construction Using Symmetry Principles, 53 MOLECULAR ORBITAL CONSTRUCTION FROM FRAGMENT ORBITALS Introduction, Triangulär H 3, Linear H 4, Rectangular and Square Planar H 4, Tetrahedral H 4, Pentagonal H 5 and Hexagonal H 6, Orbitals of 7r Systems, 71 MOLECULAR ORBITALS OF DIATOMIC MOLECULES AND ELECTRONEGATIVITY PERTURBATION Introduction, Orbital Hybridization, Molecular Orbitals of Diatomic Molecules, Electronegativity Perturbation, 82 MOLECULAR ORBITALS AND GEOMETRICAL PERTURBATIONS Molecular Orbitals ofah 2, Geometrical Perturbation, Walsh Diagrams, Jahn-Teller Distortions, 95 A. Second-Order Jahn-Teller Distortion, 95 B. First-Order Jahn-Teller Distortion, 97 C. Three-Center Bonding, Bond Orbitals, Through-Bond Interactions, 107 STATE WAVEFUNCTIONS AND STATE ENERGIES Introduction, The Molecular Hamiltonian and State Wavefunctions, The Fock Operator, State Energy, Excitation Energy, Ionizat'ion Potential and Electron Afflnity, Electron Density Distribution and the Magnitudes of Coulomb and Exchange Repulsions, Low vs. High Spin States, Electron-Electron Repulsion and Charged Species, Configurational Interaction, 125

4 CONTENTS xiii 9. MOLECULAR ORBITALS OF SMALL BUILDING BLOCKS MOsFrom Bond Orbitals, 131 A. AH, 131 B. Pyramidal AH 3, 133 C. Tetrahedral AH 4, Shapesof AH 3 Systems, 140 A. Six-Electron Systems, 141 B. Eight-Electron Systems, r-Bonding Effects of Ligands, Shapes of AH 4 Systems, MOLECULES WITH TWO HEAVY ATOMS Introduction, A 2 H 6 Systems, 152 A. Ethane, 153 B. Diborane, 155 C. Dimerization of AH 3, Twelve-Electron A 2 H 4 Systems, 158 A. Sudden Polarization, 159 B. Substituent Effects, 163 C. Dimerization of AH 2,165 D. Pyramidalization of A 2 H 4, Fourteen-Electron AH 2 BH 2 Systems, AH 3 BH 2 Systems, AH 3 BH Systems, ORBITAL INTERACTIONS THROUGH SPACE AND THROUGH BONDS Introduction, In-Plane a Orbitals of Small Rings, 184 A. Cyclopropane, 184 B. Cyclobutane, Through-Bond Interactions, 19 5 A. The Nature of Through-Bond Coupling, 195 B. Other Through-Bond Coupling Units, Breaking a C-C Bond, POLYENES AND CONJUGATED SYSTEMS Acylic Polyenes, HückelTheory, Cyclic Systems, Perturbations of Cyclic Systems, Conjugation in Three Dimensions, SOLIDS Energy Bands, Distortions of One-Dimensional Systems, 243

5 xiv CONTENTS Other One-Dimensional Systems, Three-Dimensional Systems, High Spin and Low Spin Considerations, HYPERVALENT MOLECULES Orbitals of Octahedrally Based Molecules, Geometfies of Hypervalent Molecules, TRANSITION METAL COMPLEXES-A STARTING POINT AT THE OCTAHEDRON Introduction, Octahedral ML 6, r-Effects in an Octahedron, Distortions from an Octahedral Geometry, SQUARE PLANAR, TETRAHEDRAL ML 4 COMPLEXES AND ELECTRON COUNTING Introduction, The Square Planar ML 4 Molecule, Electron Counting, The Square Planar-Tetrahedral ML 4 Interconversion, FIVE COORDINATION Introduction, The C 4 ML 5 Fragment, Five Coordination, Molecules Built up from ML 5 Fragments, Pentacoordinate Nitrosyls, THE C 2v ML 3 FRAGMENT Introduction, The Orbitals of a C 2 ML 3 Fragment, ML 3 -Containing Metallocycles, Comparison of C 2v ML 3 and C 4 ML S Fragments, THE ML 2 AND ML 4 FRAGMENTS Development of the C 2l) ML 4 Fragment Orbitals, efin-ML 4 Complexes, The C 2v ML 2 Fragment, Polyene-ML 2 Complexes, Reductive Elimination, COMPLEXES OF ML 3, MCp, AND Cp 2 M Derivation of the Orbitals for a C 3v ML 3 Fragment, The CpM Fragment Orbitals, 387

6 CONTENTS xv Cp 2 M and Metallocenes, Cp 2 ML Complexes, THE ISOLOBAL ANALOGY Introduction, Generation of Isolobal Fragments, Illustrations of the Isolobal Analogy, Extensions, CLUSTER COMPOUNDS Types of Cluster Compounds, Cluster Orbitals, Wade's Rules, 432 INDEX 441