SONO-ELECTROCHEMISTRY - THE OXIDATION OF BIS(CYCLOPENTADIENYL)MOLYBDENUM DICHLORIDE

The oxidation of [Mo(cp)(2)Cl-2] (cp = eta-C5H5) in acetonitrile solution at platinum electrodes has been studied. In the absence of ultrasound a simple one-electron oxidation with a half-wave potential of +0.5 V (vs. saturated calomel electrode) is observed together with a much smaller wave with a half-wave potential of +1.05 V. In the presence of ultrasound the first wave involves the passage of greater than one electron per molecule of electroactive species and the second wave disappears. The mechanism in equations (i)-(iii) is proposed to explain the observations. where the chemical fc) (e. = electrochemical) and the disp. (disproportionation) steps are promoted by ultrasound. (i) e. step [Mo(cp)(2)Cl-2] - e --> [Mo(cp)(2)Cl-2](+) (ii) c.step [Mo(cp)(2)Cl-2](+) +MeCN --> Cl' + [Mo(cp)(2)Cl(MeCN)](+) disp. step [Mo(cp)(2)Cl-2](+) + [Mo(cp)(2)Cl(MeCN)](+) --> (iii) [Mo(cp)(2)Cl(MeCN)(2+) + [Mo(cp)(2)Cl-2]