Air oxidation of divanadium(IV) complexes

The dinuclear VIV=O complex of 2,6-bis{[N,N-bis(2-pyridylmethyl)amino]methyl}-4-tert-butylphenolato (bpbp-), [(V=O)2bpbp(OH2)2](ClO4)3.H2O, is oxidised by air. Two products have been characterised in the solid state, namely a VVVV diperoxido complex, [(V=O)2bpbp(eta2-O2)2](ClO4), and a VVVIV trioxido complex, [V(O)2V(O)bpbp(OH2)](ClO4)(2).2H2O.EtOH, . The rate of formation of is solvent-dependent and is fastest in 2-propanol, compared to methanol or tetrahydrofuran. A transient species postulated to be a VV hydroperoxido species was detected during the course of this relatively slow reaction, which takes place on a timescale of hours to days. Concentration appears to be the factor determining whether complex or complex is obtained from reactions of with air: at higher complex concentrations formation of rather than is presumed to occur via a bimolecular reaction between the starting VIV complex and a reactive oxidized adduct.