Studies on metal complexes of ortho-quinone monooximes. Part 9. Analysis of the charge distribution within the o-quinone monooxime ligands through crystallographic data

Abstract

The known crystal structures of the o-benzoquinone monooxime complexes with d metals have been examined. In these compounds the ligands can, in principle, be present as o-benzoquinone monooximes I or o-nitrosophenols II. The available data indicate that the ligands are always intermediate between these limiting forms. Moreover, a comparison between the structures of the free ligands and those of their d-metal complexes shows that complexation to a d-metal influences the mesomeric equilibrium between forms I and II, causing a shift towards II. This feature is discussed in terms of the interaction of the ligands with the d orbitals of the metal.