Vanadium(V) Complexes of O,N,O-Donor Tridentate Ligands Containing the {V^VO(OMe)}²⁺ Unit: Syntheses, Structures and Properties

Abstract

Syntheses, characterisation and properties of two complexes containing the oxovanadium(V) methoxide unit have been described. Deprotonated benzoylhydrazones of 2–hydroxy–5–methoxy‐benzaldehyde (H₂bhsOMe) and 2–hydroxy–5–chlorobenzaldehyde (H₂bhsCl) were used as coligands. Crystal structures of both the complexes were determined. In solid state one of them is a dinuclear species [VO(bhsOMe)(OMe)]₂ (1) whereas the other one is a mononuclear complex [VO(bhsCl)(OMe)(HOMe)](2). The dinegative ligands coordinate the metal ions via phenolate–O, imine–N and deprotonated amide–O atoms. In 1, the metal ions of two square pyramidal VO(bhsOMe)(OMe) units share the methoxide groups to form a dinuclear species. The oxygen of a methanol molecule completes the hexacoordination of the metal centre in 2. In each of the two distorted octahedral VO₅N moieties of 1 the bridging methoxide oxygen and in that of 2 the methanol oxygen is trans to the corresponding oxo group. Both the complexes are redox active. The VO³⁺ to VO²⁺ reduction potentials (vs Ag/AgCl) of 1 and 2 are observed at −0.25 and −0.04 V, respectively. The band positions in the electronic spectra and the redox potentials reflect the influence of the substituents present on the ligands.

Key Words:

• Vanadium(V) complexes
• crystal structures
• solid state nuclearity
• substituent effect