Electronic structures of trans-dioxometal complexes

Abstract

We have employed computational methods based on density functional theory to elucidate the effects of equatorial ligands on the electronic structures of trans-dioxometal complexes. In complexes with ammine (σ-only) equatorial donors, the 1A1 g(b2 g)^2 → Eg(b2 g)^1(eg)^1 excitation energy increases with metal oxidation state: Mo(IV) < Tc(V) < Ru(VI) and W(IV) < Re(V) < Os(VI). Increasing transition energies are attributed to enhanced oxometal π-donor interactions in the higher valent central metals. But in complexes with cyanide equatorial donors, the 1A1 g(b2 g)^2 →Eg(b2 g)^1(eg)^1 energy remains roughly independent of metal oxidation state, likely owing to the compensating increased π-donation from the π(CN) orbitals to the metal dxy orbitals as the oxidation state of the metal increases.