SYNTHESIS, CHARACTERIZATION AND CRYSTAL-STRUCTURE OF MOLYBDENUM AND MOLYBDENUM-COPPER HYDROXY-RICH SCHIFF-BASE COMPLEXES

The reaction of hydroxy-rich Schiff bases [H(3)L = XC(6)H(3)(OH) CH=NC(R)(CH2OH)(2) where X = H, 5-CI or 5-Br and R = Me or Et] with [MoO2(acac)(2)] (acac = acetylacetonate) gave mononuclear complexes [MoO2(HL)(MeOH)]. The complexes were characterised by spectroscopic methods and by a single-crystal structure determination. Reaction of the mononuclear complexes with Ph(2)PCH(2)PPh(2) in methanol or acetonitrile led to five-co-ordinate polymeric compounds of the type [MoO(L)](n) in which the fifth position of the distorted square pyramid is occupied by the oxygen atom of a CH2O- moiety of a neighbouring repeat unit. The complex [MoO2(HL(3))(MeOH)][H(3)L(3)=2-(5-chlorosalicylideneamino)-1 ,3-dihydroxy-2-methylpropane] reacted with Cu(O(2)CMe)(2) in methanol-acetonitrile to yield the mixed-metal cluster [Cu(2)Mo(2)O(4)L(2)(3)(OMe)(2)] with a Cu2Mo2O4 cubane-like core. Reflux of this complex with an excess of 2,2'-bipyridine in acetonitrile yielded pale blue-green crystals of the tetranuclear cluster [CuMo3O8(HL(3))(2)(bipy)(2)] the structure of which has been determined by X-ray crystallography. The molybdenum part may be described in terms of three ore-bridged centres, one tetraoxomolybdate [MoO4](2-) and two six-co-ordinated MoO2(Schiff base) moieties. The magnetic properties of this compound have been studied in the temperature range 5-300 K.