BINUCLEAR DIOXOMOLYBDENUM(VI) COMPLEXES OF FLEXIBLY-BRIDGED HEXADENTATE TETRAANIONIC SCHIFFS BASES DERIVED FROM METHYLENE-BIS(SALICYLALDEHYDE) OR DITHIO-BIS(SALICYLALDEHYDE) AND S-METHYLDITHIOCARBAZATE OR S-BENZYLDITHIOCARBAZATE

The flexibly-bridged hexadentate tetraanionic ligands, LH(4) [LH(4)=Sc hiff's bases obtained by the condensation of methylene- or dithio- bis (salicylaldehyde) with S-methyldithiocarbazate and S-benzyldithiocarba zate], react with [MoO2(acac)(2)] in a 1:2 molar ratio in refluxing me thanol to give complexes of the type [(MoO2)(2)L]. These complexes sho w an intense v(Mo=O) band at 924-948 cm(-1) and a broad but strong ban d at ca. 850 cm(-1) due to weakened v(Mo=O) as a result of Mo - O-iMo interactions. An oligomeric structure, in which each Mo(VI) ion achiev es a pseudo-octahedral structure via Mo - O-->Mo bridging, has been su ggested for these complexes. [(MoO2)(2)L] reacts with monodentate liga nds (D) like pyridine, 4-methylpyridine, and dimethylsulfoxide and for ms six-coordinated complexes of the type [(MoO2)(2)L(D)(2)] which are monomers. Cyclic voltammetry measurements indicate that these (MoO2)-O -VI complexes are resistant to (MoO)-O-IV reduction.