Vanadium(IV/V) Complexes Containing [VO]2+, [VO]3+, [VO2]+ and [VO(O2)]+ Cores with Ligands Derived from 2-Acetylpyridine andS-Benzyl- orS-Methyldithiocarbazate

Abstract

Vanadium complexes containing [VO]2+, [VO]3+, [VO2]+ and [VO(O2)]+ cores with ligands (LH) derived from 2-acetylpyridine and S-benzyldithiocarbazate (Hacpy-sbdt, I) or S-methyldithiocarbazate (Hacpy-smdt, II) are introduced. The dioxovanadium(V) complexes [VO2L] [HL = I (2), II (5)] were isolated from the reaction between LH and [VO(acac)2] in the presence of air and KOH in dry methanol. Treatment of II with aerated [VO(acac)2] in wet methanol yielded the malonato complex [VO(acpy-smdt)mal] (6), with the malonate ligand originating from acetylacetonate. Under anaerobic reaction conditions, LH replaced one of the acac(1−) ligands to yield the oxovanadium(IV) complexes [VO(acac)L] [HL = I (1), II (4)]. Treatment of these complexes with H2O2, catechol or benzhydroxamic acid gave rise to oxo(peroxo)vanadium complexes [VO(O2)L] [HL = I (3), II (7)], catecholato complexes [VOL(cat)] [HL = I (8), II (9)] or benzhydroxamato complexes [VOL(bha)] [HL = I (10), II (11)]. Compounds 3 and 7 were capable of transferring an oxo group to PPh3. In the presence of L-ascorbic acid under aerobic conditions, 8 and 11 were converted into 2 and 5, possibly through intermediate reduction. Acidification of 2 with HCl in methanol afforded a hydroxo(oxo) complex. The crystal and molecular structures of 2 and 6 were determined, confirming the NNS (enethiolate) binding mode of L−, and the bidentate coordination of the malonate ligand in 6. The geometrical arrangement of the ligand set in 2 is intermediate between a trigonal bipyramid and a tetragonal pyramid. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)