Synthesis and Characterization of Dioxomolybdenum(VI) Complexes with Tridentate O,N,S-Donor Schiff Bases and 4,4'-Bipyridyl Ligand

The presence of the cis-dioxomolybdenum (VI) cation, [MoO2]2+, in the oxidized forms of specific molybdoenzymes has stimulated both the search for new structures in which half of this work is coordinated to Schiff base ligands containing oxygen, nitrogen or sulfur donors. The tautomerism of these ligands as well as the well known tendency of sulfur donors to act as bridging ligands allows various structural possibilities for the corresponding metal complexes. The reaction of MoO2(acac)2 with the equimolar Schiff base ligands, which are derived from salicylaldehyde and S-methyldithiocarbazate, and bidentate ligand in methanol, led to the mononuclear dioxomolybdenum(VI) complexes of the type of [MoO2 (Schiff base)(S)](L) (S=CH3OH or H2O). However, these three dioxomolybdenum(VI) complexes synthesized contain one uncoordinated 4,4'-bby or 4,4'-dpdo molecule per asymmetric structural unit, which is not common and is noteworthy.