Dioxomolybdenum(VI) complexes of new binucleating schiff bases derived from methylene- or dithio-bis(salicyclaldehyde) and various amines

Abstract

The syntheses of binuclear dioxomolybdenum(VI) complexes of the type [(MoO2)2L], where L is a flexibly-bridged hexadentate tetraanionic Schiff base derived from the condensation of methylene- or dithio-bis(salicylaldehyde) with o-aminophenol, 2-aminoethanol, 2-amino-2-methyl propanol 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 MoO---Mo bridging. Treatment of [(MoO2)2L] with pyridine leads to the formation of [MoO2)2L(py)2] in which pyridine binds at the sixth labile binding sites in both [MoO2]2+ units. [(MoO2)2L(py)2] is readily convertable inot [(MoO2)2L] at ca 180°C in a single endothermic step, as seen from their DTA analysis. The pyridine adducts show two IR absorption at ca 900 cm-1, attributable to a cis-MoO2 structure, whereas the oligomeric complexes usually show one intense ν(MoO) band at 910-938 cm-1 and a broad but strong band at ca 820 cm-1 due to a weakend ν(MoO) band as a result of MoO → Mo interactions. © 1993.