Dioxomolybdenum(VI) and dioxotungsten(VI) complexes of isomeric ONO donor ligands and the X-ray crystal structure of [MoO2(o-OC6H4CH=NCH2C6H4O)(MeOH)](2)center dot MeOH

Dioxomolybdenum(VI) and dioxotungsten(VI) complexes of two isomeric Schiff bases derived from salicylaldehyde, 2-hydroxy-1-naphthaldehyde and o-hydroxybenzylamine or o-aminobenzylalcohol have been prepared and characterized. H-1 NMR spectral data confirm the formation of [MO2L] (M = Mo or W, LH2 = ligand) types of complexes except the complex of dioxomolybdenum(VI) with the ligand salicylaldehyde-o-hydroxybenzylamine (H(2)sal-OHYBA) which forms [MoO2(sal-OHYBA). CH3OH]. An X-ray Study of [MoO2(sal-OHYBA) CH3OH] shows the presence of distorted octahedral geometry around molybdenum in which the tridentate ligand occupies meridional position where two anionic oxygens are mutually trans and are cis to the cis dioxo group. Generally the tungsten complex is more stable to decomposition than the molybdenum one within the same ligand. (C) 1997 Elsevier Science Ltd.