Vanadium( V ) Oxoperoxo Complexes with Side Chain Substituted N ‐Salicylidenehydrazides: Modeling Supramolecular Interactions inVanadium Haloperoxidases

The Schiff‐base ligand derived from salicylaldehyde and γ‐hydroxybutanoic acid hydrazide (H 2 Salhyhb) reacts with potassium metavanadate and hydrogen peroxide in a water/methanol solution with a pH value of around two to yield the corresponding vanadium( V ) oxoperoxo complex [VO(O 2 )HSalhyhb(H 2 O)] ( 1 ). Complex 1 crystallizes with one molecule of water as 1· H 2 O in the monoclinic space group P 2 1 / n . For the vanadium atom a pentagonal‐bipyramidal coordination geometry is observed, with a side‐on bonded peroxo ligand in the equatorial plane. The hydroxy side chain of the hydrazide ligand is involved in a hydrogen‐bond network with the peroxo ligand at the vanadium atom. This network shows some similarities with the hydrogen‐bonding scheme found for the peroxo form of vanadium haloperoxidases. The stoichiometric reaction of 1 with 1,3,5‐trimethoxybenzene (TMB) in the presence of tetrabutylammonium bromide leads to the formation of 1‐bromo‐2,4,6‐trimethoxybenzene (Br‐TMB), thus mimicking the oxidative halogenation function of the native enzyme. Complex 1 is also capable of oxidizing triphenylphosphane and methylphenylsulfane, yielding a cis ‐dioxovanadium( V ) complex and the corresponding phosphane or sulfane oxide, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)