This second edition was updated to include some of the recent developments, such as “increased-valence” structures for 3-electron-3-centre bonding, benzene, electron conduction and reaction mechanisms, spiral chain O4 polymers and recoupled-pair bonding. The author provides qualitative molecular orbital and valence-bond descriptions of the electronic structures for primarily electron-rich molecules, with strong emphasis given to the valence-bond approach that uses “increased-valence” structures. He describes how “long-bond” Lewis structures as well as standard Lewis structures are incorporated into “increased-valence” structures for electron-rich molecules. “Increased-valence” structures involve more electrons in bonding than do their component Lewis structures, and are used to provide interpretations for molecular electronic structure, bond properties and reactivities. Attention is also given to Pauling “3-electron bonds”, which are usually diatomic components of “increased-valence” structures for electron-rich molecules.
Atomic Orbitals, Electron Spin, Linear Combinations.- Pauling ‘3-Electron Bonds’, 4-Electron 3-Centre Bonding, and the Need for an ‘Increased Valence’ Theory.- Wave-Functions and Valence-Bond Structures for 1-Electron Bonds, Electron-Pair Bonds, Pauling ‘3-Electron Bonds’ and ‘No Bonds’.- Valence-Bond Structures for Some Diatomic Molecules.- Pauling ‘3-Electron Bonds’ and Hypoligated Transition Metal Complexes.- Pauling ‘3-Electron Bonds’, 5-Electron 3-Centre Bonding and Some Tetra-Atomic Radicals.- Some Dimers of Triatomic Radicals with 17 and 19 Valence-Shell Electrons.- Some Cu(II) Binuclear Transition-Metal Complexes.- Excited States.- Pauling ‘3-Electron Bonds’ and ‘Increased Valence’ Theory for N2O4.- Pauling ‘3-Electron Bonds’ and ‘Increased-Valence’ Structures.- Increased-Valence Structures Constructed from Lewis Structures: Delocalization of Lone-Pair Electrons into Vacant Bonding Orbitals.- ‘Increased-Valence’ Structures for N-Centre Bonding Units.- Delocalization of Lone-Pair Electrons into Antibonding Orbitals: Increased-Valence Structures, Molecular Orbital Theory and Atomic Valencies.- Slater Determinants and Wave-Functions for ‘Increased-Valence’ Structures.- Classical Valence Structures and Quinquevalent Nitrogen Atoms.- Some Tetrahedral Molecules and dπ − Pπ Bonding for Some Sulphur Compounds.- Transition Metal Complexes with CO, N2, NO and O2 Ligands.- Some Electron-Excess σ Bonded Systems.- Intermolecular Donor-Acceptor Complexes.- Base-Displacement Reactions and Electron Conduction in Alkali Metals.- Free-Radical and Spin-Paired Diradical Reactions.- Some Comparisons of Types of Wave-Functions for 4-Electron 3-Centre Bonding Units.- A Note on Pauling ‘3-Electron Bonds’ and Covalent-Ionic Resonance.- Valence-Bond Representations for 3-Electron 3-Centre Bonding.