Transition metal imido complex

In coordination chemistry and organometallic chemistry, transition metal imido complexes is a coordination compound containing an imido ligand. Imido ligands can be terminal or bridging ligands. The parent imido ligand has the formula NH, but most imido ligands have alkyl or aryl groups in place of H. The imido ligand is generally viewed as a dianion, akin to oxide.

In some terminal imido complexes, the M=N−C angle is 180° but often the angle is decidedly bent. Complexes of the type M=NH are assumed to be intermediates in nitrogen fixation by synthetic catalysts.

Imido ligands are observed as doubly and, less often, triply bridging ligands.

Commonly metal-imido complexes are generated from metal oxo complexes. They arise by condensation of amines and metal oxides and metal halides:

This approach is illustrated by the conversion of MoO₂Cl₂ to the diimido derivative MoCl₂(NAr)₂(dimethoxyethane), precursors to the Schrock carbenes of the type Mo(OR)₂(NAr)(CH-t-Bu).

Aryl isocyanates react with metal oxides concomitant with decarboxylation:

Some are generated from the reaction of low-valence metal complexes with azides:

A few imido complexes have been generated by the alkylation of metal nitride complexes: