ORGANOMETALLIC PHOTOELECTROCHEMISTRY - OXIDATION OF FAC-TRICARBONYLCHLORO[BIS(DIPHENYLPHOSPHINO)METHANE]MANGANESE(I)

The electrochemical oxidation of fac-tricarbonylchloro[bis(diphenylphosphino)methane]manganese(I) (FCM) has been studied at an irradiated (390-nm) channel electrode. Photocurrent measurements made as a function of variable mass transport, combined with simultaneous photoelectrochemical ESR measurements, have shown that new electrode reaction pathways appear under illumination. Specifically, first, light can induce a fac to mer isomerization in the molecule which leads to oxidation at potentials lower than those required in the dark, and this process has been quantitatively interpreted as a photo-CE (C = chemical step; E = electrode step) mechanism. Second, the direct oxidation of FCM is modified under illumination with enhancement of the current flowing. A modified disproportionation mechanism was found to uniquely and quantitatively describe the process. In both cases the relevant rate constants are reported.