Partial charges as reactivity descriptors for nitrido complexes

The experimental trend observed for the reactivity of d-block nitrido complexes is one of increasing electrophilicity of the nitrogen ligand, upon going from early (group 4) to later (group 8) transition metals. Accordingly nitrido complexes of group 8 frequently react with electron donors despite the formal N3− formulation of the nitrido ligand would suggest nucleophilic behaviour. A number of typically applied population analyses from the literature have been used in a DFT framework to investigate their ability to reproduce this observed trend. It is found that population analyses in comparative studies are valuable tools and that the partial charges on the nitrogen atom vary in accordance with experimental reactivity for a set of model complexes with a fixed ligand sphere and oxidation state. Both negatively charged, [M(N)Cl4]2−, and neutral complexes, [M(N)salen], (in both cases M = VV, CrV, MnV and FeV) follow this trend.