Trinuclear Clusters of the Early Transition Elements

Trinuclear clusters of the early transition elements, i.e. those elements situated on the left‐hand side of the transition series, represent the simplest types of clusters. They characteristically have a pronounced formation tendency and high stability; they are therefore produced under a wide variety of conditions and their triangular M 3 skeleton is conserved in ligand exchange reactions. These clusters play a very important role in the chemistry of the respective elements, and especially those of the 4 d and 5 d series. Biochemical implications are of interest in connection with Mo IV . This progress report presents a systematic account of the chemistry and the molecular and electronic structure of such compounds. A connection is also established with the crystal field treatment of mononuclear metal complexes.