Chemical Laboratories, D. S. College, Aligarh, Aligarh-202 001 Manuscript received 23 July 1979, accepted 29 December 1979 The complexes of molybdenum(VI) with 2-hydroxy-5-chloro and 2-hydroxy-5-bromo acetophenone oximes have been studied spectrophotometrically in water-ethanol medium. The yellow coloured solid complexes of above ligands were isolated by refluxing the metal and ligand solutions in stoichiometric ratio. These complexes were characterized by analytical, thermal, infra-red spectra) and magnetic susceptibility data. The composition of above complexes comes out to be 1:2 (metal:ligand), the general formula being MoO2 (C6H7O2NX)2 ; where X=CI and Br. Their spectral study of complexes show that these ligands act as bidentate ligand with molybdenum(VI) and coordination takes place by formation of M-O and M���N bonds through the oxygen of phenolic group and nitrogen of oxime group with metal. The magnetic susceptibility data reveals that complexes are diamagnetic, octahedral in nature and molecular weights determined by cryoscopic met bod show the monomer character. The stability constants are 5.5 x 108 and 2.31 x 108 ; and free energy of formation ��F�� are -12.11 and -11.59 K cal/mol in case of 2-hydroxy-5-chloro acetophenone oxime and 2-hydroxy-5-bromo acetophenone oxime respectively, determined spectrophotometrically applying the Mole-Ratio method.