cis-dioxovanadium(V) and mixed-valence divanadium(IV, V) complexes containing β-diketonate and heterocyclic nitrogen-base ligands

Diamagnetic dioxovanadium(V) complexes, VO2(β-dik)(phen or bpy), were prepared by the direct reactions of VO(β-dik)2 with 1,10-phenanthroline and 2,2'-bipyridine in dichloromethane under aerobic conditions as well as by two other methods. These compounds were concluded to have a cis configuration on the basis of the IR and Raman data. These complexes are solvolyzed to afford the di-μ-methoxo- or di-μ-hydroxo-divanadium(V) species, and are reduced by hydrogen bromide to the oxovanadium(IV) species in dichloromethane. In methanol instead of dichloromethane, VO(acac)2 reacted with 2,2'-bipyridine to produce a novel mixed-valence divanadium(IV, V) complex, V2O3(acac)3(bpy), which was revealed by the magnetic, spectral, and polarographic data to be a trans adduct of VO(acac)2 with VO2(acac)(bpy) via an oxide ligand. (auth.)