General Topics

Abstract

This introductory chapter starts by a brief history of the subject from the discovery by Zeise of a platinum-ethylene complex in 1827 to the last Nobel prizes awarded to Heck, Negishi, and Suzuki in 2010 for their work on palladium-catalyzed carbon–carbon coupling reactions. Then, the electronic characteristics of the transition metals are presented (number of d electrons, electronegativities), together with the shapes of the atomic d orbitals. The various types of ligands are introduced with their coordination modes, terminal, bridging, mono- and polyhapto. The special cases of CO, NO are discussed. The molecular orbitals of ML₆, ML₅, ML₄, ML₃, and ML₂ complexes are qualitatively studied. In each case, the structure of the d block is deduced from that of ML₆ using simple geometrical arguments. The main types of reactions of transition metal complexes are defined, including substitution, oxidative addition, reductive elimination, oxidative coupling, reductive decoupling, 1, 1 and 1, 2 migratory insertions, nucleophilic and electrophilic attacks on coordinated ligands. For each type, the main mechanisms are discussed with their consequences for the electronic structures of the complexes. All this introductory material can serve to decipher the modern literature on transition metal chemistry together with its applications in catalysis and synthetic organic chemistry.