Synthesis and characterisation of new binuclear oxo-vanadium(IV) complexes with a bis(bidentate)oxalate bridge. Crystal structures of the cationic and anionic complexes

International audienceThe new oxalate - vanadyl compounds [V2O2(C2O4)(H2O)6]Cl2 4Bu4NCl H2O (1) (Bu=C4H9) and [Et4N]4[V2O2(C2O4)(NCS)6] (2') (Et = C2H5) have been synthesized starting from V2O5 and VOSO4 5H2O, respectively. Metathesis of 2' with [FeCp2*]BF4 (Cp* = CS(CH3)5) gave a partial substitution of the cations affording FeCp2*]2[Et4N]2[V2O2(C2O4)(NCS)6] (2). The X-ray structures of 1 and 2 have been determined. In both complexes, which crystallise in the monoclinic space group P21/c, the centrosymmetric binuclear vanadium species present a bis(bidentate)oxalate ligand and an almost planar [V2O2(C2O4)X2] unit (X = O(H2O) for 1 and N(NSC) for 2)with two V = O groups located in trans positions in the equatorial plane. In both cases, the strong V = O terminal bond (1.569(7) in 1, 1,580(7) Å in 2) has a strong trans influence which is slightly greater in the cation of I than in the anion of 2. Magnetic susceptibility measurements indicate weak antiferromagnetic pairwise interactions for 1, 2 and 2'. (C) 2000 Elsevier Science S.A