Polynuclear Organometallic Cluster Complexes

Abstract The title refers to molecular compounds containing three or more transition metal atoms and hydrocarbyl ligands as a part of the metal–carbon cluster core. Because the chemistry of trimetallic clusters is the most well developed, these examples are to be stressed. Selected examples are presented to illustrate the principles of structure and bonding of organometallic clusters, synthetic approaches, and chemical reactions, including ligand substitution, oxidative addition, intramolecular insertion, protonation of metal–metal bonds and coordinated ligands, nucleophilic attack on coordinated ligands, and ligand fluxionality. The chemistry of these clusters is exemplified by trimetallic clusters containing hydrocarbon fragments of one, two, or three carbon atoms. While, many of the features of cluster chemistry are common with those of organometallic complexes containing a single metal atom, there are notable differences in structures and reactivities owing to the tendencies of ligands to bridge between two or more metal atoms and for ligands bound to only a single metal atom to undergo facile intramolecular migrations between metal atoms. These distinctions give rise to the ‘metal‐cluster‐metal surface analogy’ in which structural and spectroscopic features of organometallic clusters are used as models for hydrocarbons chemisorbed on metal surfaces.