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

The oxidation of [Mo(cp)(2)Cl-2] (cp = eta-C5H5) in acetonitrile solut ion at platinum electrodes has been studied. In the absence of ultraso und 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 el ectron per molecule of electroactive species and the second wave disap pears. The mechanism in equations (i)-(iii) is proposed to explain the observations. where the chemical fc) (e. = electrochemical) and the d isp. (disproportionation) steps are promoted by ultrasound. (i) e. ste p [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(c p)(2)Cl-2]