DIOXOMOLYBDENUM(VI) COMPLEXES OF NEW BINUCLEATING SCHIFF-BASES DERIVED FROM METHYLENE-BIS(SALICYLALDEHYDE) OR DITHIO-BIS(SALICYLALDEHYDE) AND VARIOUS AMINES

The syntheses of binuclear dioxomolybdenum(VI) complexes of the type [ (MoO2)2L], where L is a flexibly-bridged hexadentate tetraanionic Schi ff base derived from the condensation of methylene- or dithio-bis(sali cylaldehyde) with o-aminophenol, 2-aminoethanol, 2-amino-2-methyl prop anol or 1-amino-2-propanol, are reported. The IR and NMR spectral data suggest an oligomeric structure in which each molybdenum ion achieves a pseudo-octahedral structure via Mo=O---Mo bridging. Treatment of [( MoO2)2L] with pyridine leads to the formation of [MoO2)2L(py)2] in whi ch pyridine binds at the sixth labile binding sites in both [MoO2]2+ u nits. [(MoO2)2L(py)2] is readily convertable into [(MoO2)2L] at ca 180 -degrees-C in a single endothermic step, as seen from their DTA analys is. The pyridine adducts show two IR absorptions at ca 900 cm-1, attri butable to a cis-MoO2 structure, whereas the oligomeric complexes usua lly show one intense nu(Mo=O) band at 910-938 cm-1 and a broad but str ong band at ca 820 cm-1 due to a weakened nu(Mo=O) band as a result of Mo=O --> Mo interactions.