Cyclopentadienyl and related complexes of the group 6 elements having metal–metal triple bonds: Synthesis, structure, bonding and reactivity

• Triple bonds are very reactive towards an immense variety of molecules.
• Triple bonds promote the formation of unusual geometries and coordination modes.
• Triple bonds promote the mild formation and cleavage of many different bonds.

The aim of this review is to cover the literature of the last 25 years concerning the synthesis, structure, bonding, and reactivity of compounds of the group 6 elements having metal–metal triple bonds and bearing cyclopentadienyl (η5-C5H5) or related ligands.