Imido ligands importance

Imido-ligands, NR, are isoelectronic with the oxo ligand and should produce complexes of similar types. However, there are two important differences between NR and The imido-group has better electron-donating capabilities and the fact that with the substituent R the steric requirements of this ligand can be controlled within a wide range. This allows the stabilization of imido species with low coordination numbers and with ligands which are easily oxidized. 

Coordinated nitrenes RN2- have been thoroughly investigated in recent years285,286 owing to their formal similarity to carbenes and to their potential importance, e.g. as catalysts in the Haber ammonia process. Theoretical studies have suggested that imido ligands may also prove effective in promoting alkene metathesis.287... 

Group 4 imido chemistry see Imide Complexes) is less well studied than that of the group 5-7 metals. An important reason for this is the change in reactivity of the imido ligand upon coordination to the more electropositive metals. The increased polarity of the M=NR unit in compounds... 

The 1,2-addition of C—H bonds across metal-heteroatom bonds has been reported for two different classes of complexes early transition metal d° complexes with imido ligands and late transition metal complexes with amido, hydroxo, and aryloxo ligands (Scheme 11.36). These transformations are potentially related to o-bond metathesis reactions discussed above however, the presence of a lone pair on the heteroatom that receives the activated hydrogen may impart important differences. 

Details concerning the mechanism of forming these Re(V) metallacyclopentene complexes are not yet available. Knowing the precise mechanism is extremely important because these results may have some relevance to the question concerning the mechanism of 3+2 cycloadditions involving olefins and oxo or imido ligands in Os(VIII)... 

In the imido systems the n n transition is shifted to lower energy (518 nm) and markedly decreases in intensity. On the other hand, upon substitution of the anionic trans-ligands by acetonitrile the n->-n transition is found at 450 nm, shifting to 525 nm upon protonation. Moreover, the metal-N(nitrido) stretching frequency increases to 1016 cm From a chemical viewpoint it is important that the nitrido-nitrile complex can be... 

The [Tc=N] core is second only to the [Tc=0] core in its importance for the coordination chemistry of technetium in the context of radiopharmaceutical applications. The nitrido ligand N is isoelectronic with the 0x0 o ligand and with the imido R—ligand. The highly negative charge makes the nitrido ligand a very powerful rr-donor, well able to stabilize the... 

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