The Schiff-base ligand derived from salicylaldehyde and γ-hydroxybutanoic acid hydrazide (H2Salhyhb) 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(O2)HSalhyhb(H2O)] (1). Complex 1 crystallizes with one molecule of water as 1·H2O in the monoclinic space group P21/n. For the vanadium atom a pentagonal-bipyramidal coordination

The water soluble ammonium salts of cis-dioxovanadium(v) complexes with side chain functionalized N-salicylidenehydrazides show hydrogen bonding interactions relevant for haloperoxidase enzymes. Under turnover conditions for the catalytic bromination of trimethoxybenzene, no substitution of the side chain hydroxy group is observed.