Biomimetic oxo-, dioxo- and oxo-peroxo-hydrazonato-vanadium(IV/V) complexes

摘要

[VO(acac)_2] reacts with HL (HL is the hydrazone Hacpy-inh I, or Hacpy-bhz II; acpy = acetylpyridine, inh = isonicotinic acid hydrazide, bhz = benzoylhydrazide) in dry methanol to yield the oxovanadium(IV) complexes [VOL(acac)] (HL = I:1 HL = II:3). The dioxovanadium(V) complexes [VO_2L] (HL = I:2, HL = II:4) are obtained by aerial oxidation of 1 and 3 in methanol. Treatment of 1 and 3, or 2 and 4, with H_2O_2 yields the oxoperoxovanadium(V) complexes [VO(O_2)L] (HL = I:5, HL = II:6). In the presence of catechol or benzohydroxamic acid, 1 and 3 give the mixed chelate complexes [VOL(cat)] (HL = I:7; HL = II:8), or [VOL(bha)] (HL = I:9, HL=II:10). The peroxo complexes 5 and 6 undergo oxygen transfer reaction with PPh_3 in DMF. In DMF and DMSO, 7,8,9 and 10 showly convert to the corresponding dioxo species 2 and 4. Acidification of 2 and 4 with HCl dissolved in methanol affords oxo-hydroxo complexes. Reaction of 7 with L-ascorbic acid yields 2. The crystal and molecular structures of 2 and 4 have been determined, confirming the ONN binding mode of I and II from their enolate form.