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The synthesis and characterization of the first unique binuclear manganese(I) salicylate complex is described. The structure of the complex is unequivocally established with the help of an X-ray crystallographic study. The structure consists of two [MnO 6 ] units, containing octahedral Mn I ions, linked together by a bridging salicylato (Hsal ) ) ligand and each Mn I is chelated with a (H 2 sal) ligand. The complex possesses a metal oxidation state of +1 and is a rare example of a noncarbonyl or cyanide complex of a binuclear Mn I species. The effective magnetic moment per binuclear molecule ( l eff: ) at 27°C is 8.07 l B; that also describes the manganese (+1) oxidation state.

The binuclear copper complex [Cu(H 2 slox)] 2 (1) and heterobinuclear copper and molybdenum complexes [Cu(slox)MoO 2 (A) 2 ] (slox ¼ tetranegative disalicylaldehyde oxaloyldihydrazone) (A ¼ H 2 O (2), py (3), 2-pic (4), 3-pic (5), 4-pic (6)) and [Cu(slox)MoO 2 (NN)] (NN ¼ bpy (7) and phen (8)) have been synthesized from disalicylaldehyde oxaloyldihydrazone in methanol and characterized by various physico-chemical and spectroscopic techniques. The stoichiometry of the complexes has been established based on elemental analyses and thermoanalytical studies. The m eff values for the complexes rule out metal-metal interaction between the metal centers in the structural unit of the complexes. The dihydrazone has keto-enol forms; in 1, it is a dibasic tetradentate bridging ligand in enol form and in heterobinuclear complexes as a tetrabasic hexadentate bridging ligand. Electronic spectra of the complexes show that copper(II) is square-planar in binuclear and heterobinuclear complexes; molybdenum is a distorted octahedral stereochemistry in heterobinuclear complexes. EPR spectra suggest that in all complexes, the unpaired electron is in the d x2Ày2 orbital of copper and that the copper in heterobinuclear complexes is tetrahedrally distorted.

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