Thermoanalytical studies of oxovanadium(IV)hydroxamate complexes

The thermal decomposition behavior of oxovanadium(IV)hydroxamate complexes of composition [VO(acac)(C₆H₅C(O)NHO)] (I), [VO(C₆H₅C(O)NHO)₂] (II), [VO(acac)(4-ClC₆H₄C(O)NHO)] (III), [VO(4-ClC₆H₄C(O)NHO)₂] (IV) (where acac = (CH₃COCHCOCH₃ ^–) synthesized from the reactions of VO(acac)₂ with equi- and bimolar amounts of potassium benzohydroxamate and potassium 4-chlorobenzohydroxamate in THF + MeOH solvent medium has been studied by TG and DTA techniques. TG curves indicated that complexes I, II, and IV undergo decomposition in single step to yield VO₂ as the final residue, while complex III decomposes in two steps to yield VO(acac) as the likely intermediate and VO₂ as the ultimate product of decomposition. The formation of VO₂ has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stability for the complexes has been inferred as IV > I > III > II.