SYNTHESIS, CHARACTERIZATION AND ELECTROCHEMICAL STUDIES OF OXIMATO-BRIDGED BINUCLEAR OSMIUM(II)-OXOVANADIUM(IV) COMPLEXES

The reaction of facial-[OsA(3)](-) (3 [A = anion of arylazo oxime (HA, 1)] with VO(acac)(2) furnishes hetero-bimetallic complexes of the typ e [OsA(3)VO(acac)](4). Replacement of acac neutral N,N donors (B) like 2,2'-bipyridine and 1,10-phenanthroline gives cationic species of the type [OsA(3)VO(B)](+) isolated as perchlorate salt 5. Extrusion of 4 and 5 with NaOH reverts to mononuclear 3. All the complexes have been characterized using their spectroscopic, magnetic and physicochemical results. A 1:1 correspondence in the IR spectra of 4 (A = A(2)) and co rresponding well-characterized iron-vanadium analogue, [FeA(3)(2)VO(ac ac)] suggests cognate structure 6. The new binuclear complexes are one -electron paramagnets and VO2+ core is EPR-active. The g-values sugges t the occupancy of the unpaired electron in d(xy) orbital. The complex es show a number of charge-transfer transitions in 200-700 nm region a nd exhibit nearly reversible osmium(III)-osmium(II) couple.