Trinuclear metallacycles: metallatriangles and much more

This review article is intended to be a comprehensive, and yet critical, collection of the trinuclear metallacycles described to date. The main focus will be on the geometry of the metallacycles: the synthetic pathway leading to these species will not be used as a discriminating factor. In most cases, they were obtained (either on purpose or not) according to the principles of self-assembly, i.e., by the combination of metal fragments with two labile ligands (either with a trans or, more often, cis geometry) and ditopic linkers. However examples of trinuclear cyclic compounds obtained by different synthetic pathways (e.g., transformation of mononuclear metal complexes or metal-induced transfor- mation of added reagents) will be equally considered.