Transition Metal Organoimido (Nitrene) Complexes

Bonding modes:

The majority of structurally characterized imido complexes exhibit linear, or near linear, geometries with M-N-C bond angles in the range 160-180°. Theoretical studies suggest that the metal-ligand bond order is usually intermediate between two and three, and that there is a rather soft potential for bending giving rise to the relatively wide range of observed bond angles. In valence-bond terms, the nitrogen in linear imidos is sp-hybridized, resulting in a formally triple M-N bond. There are only a few reported examples of strongly bent imido complexes, and the bending in these is attributed either to the steric constraints of a chelate ring or to electronic effects. In the limiting case of a strongly bent imido ligand, the N atom would be sp²-hybridized with a formally double M-N bond, and a non-bonding electron pair localized on the nitrogen. There are also a number of linear imidos for which a formally triple M-N bond would result in a violation of the 18-electron rule, and such compounds are best described as possessing a double MN bond.

Reference:
Wigley, D. E. Prog. Inorg. Chem. 1994, 42, 239, and references therein.

Examples of bent imidos:

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