Specific features of the chemical structure of the oxo-complexes of d° and d² metals with monodentate and polydentate ligands

The structure of the oxo-complexes of transition d0 and d2 Group V–VII metals is discussed. Two types of distortion isomerism are considered: the trans-influence isomerism (the lengthening of the M=O multiple bond on passing from one isomer to another is accompanied by a shortening of the M–Ltrans bond) and the multiple bond isomerism (the lengthening of the M=O bond is not accompanied by a shortening of the M–Ltrans bond). The choice of the trans-partner out of the set of competing functional groups for the d0 metal is determined by the self-consistency principle, while for the d2 metal the rule becomes more complex and the choice of the trans-partner of the oxo-ligand depends on the individual features of the trans-ligand (on the combination of its σ- and π-donor properties). It is shown in relation to the d0-MoO2 and d2-ReO complexes with isotypical chelate O, N-donor ligands that the latter are coordinated to the metal in different ways. The bibliography includes 58 references.