The reaction of VO(acac) 2 with the ONO-chelator obtained by the condensation of salicylaldehyde with 2-hydroxybenzoylhydrazine (H 2 L) in a monohydric alcohol (ROH) medium produces [VO(OR)L]-type oxidoalkoxido complexes (1-7) where R = Me, n Pr, i Pr, n Bu, i Bu, t Bu and n Pen. All the complexes show the metal atom to have a five-coordinate square pyramidal environment, although in some complexes there is an additional weak V⋯O interaction in the sixth axial position. In acetonitrile medium and in the presence of a cis-diol (ethylene glycol), H 2 L reacts with VO(acac) 2 to form a six-coordinate complex, [VO(OCH 2 CH 2 OH)L] (8). When the reaction is carried out in acetonitrile medium in the presence of 2-amino ethanol, a completely different type of product containing the square pyramidal complex anion [VO 2 L] - associated with the cation [NH 3 CH 2 CH 2 OH] + is obtained. It was noted previously that on being reacted with monodentate nitrogen donor bases B (which are stronger than pyridine), the [VO(OR)L] complexes react to form the same complex anion [VO 2 L] - associated with the corresponding cation [BH] + . The coordination environment around the V(V) acceptor center of the water soluble [BH] + [VO 2 L] - satisfies one of the several requirements for an efficient antidiabetic vanadium species such as water solubility, nature of donor atoms of the ligand and their disposition around the VO 2+ acceptor center. © 2011 Elsevier Ltd. All rights reserved.