Sono-electrochemistry: the oxidation of bis(cyclopentadienyl)molybdenum dichloride
Abstract
The oxidation of [Mo(cp)2Cl2](cp =η-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 +0.5V (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 (c.)(e. = electrochemical) and the disp. (disproportionation) steps are promoted by ultrasound.
e. step [Mo(cp)2Cl2]– e–→[Mo(cp)2Cl2]+(i), c. step [Mo(cp)2Cl2]++ MeCN → Cl·+[Mo(cp)2Cl(MeCN)]+(ii), disp. step [Mo(cp)2Cl2]++[Mo(cp)2Cl(MeCN)]+→[Mo(cp)2Cl(MeCN)]2++[Mo(cp)2Cl2](iii)