Electrochemical and spectroscopic studies of molybdenum(VI) complexes with aminopolycarboxylic acids

The complexes of molybdenum(VI) with iminodiacetic acid (IDA), nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) were investigated by means of polarographic and spectroscopic methods. The composition of the complexes was determined by the Job's method as following: 1Mo(VI)/1IDA; 1Mo(VI)/1NTA and 2Mo(VI)/1EDTA. The polarographic wave height was fairly dependent on the nature of the complexes. The overall reaction rate for the reduction of Mo(VI)-IDA complex was limited by diffusion. On the other hand, the polarographic reduction of Mo(VI)-NTA and - EDTA complexes were kinetically controlled by the preceding chemical reaction which was composed of protonation, dimerization and substitution of ligands, however, the rate-determining step was the substitution of ligands. The mechanism for the electroreduction of each complex was discussed.