Electron transfer in organometallic clusters. 9. Redox chemistry of RCCo3(CO)8PPh3 and RCCo3(CO)9-n (L-L)n (L-L ≡ polydentate ligands)

Article abstract of DOI:10.1021/om00137a011

Electrochemical studies of RCCo₃(CO)₈PPh₃, [RCCo₃(CO)₈]₂(μ-dppe), RCCo₃(CO)₇9μ -dppe) (or dppm), RCCo₃(CO)₅(dppm)₂, and RCCo₃(CO)₆(tpme) (R = Ph, CH₃) are described. Although the primary reduction step is one-electron for all derivatives, a fast ECE process gives rise to an overall two-electron diffusion currents for the primary wave unless the Co-Co bond is spanned by a chelate ligand. The i-E responses for [RCCo₃(CO)₈]₂dppe and RCCo₃(CO)₈PPh₃ are also complicated by ECE and EC reactions and are solvent dependent. An explanation is offered on the basis of fast ligand dissociations with the radical anions RCCo₃(CO)₈L^-· and RCCo₃(CO)₈(L-L)^-· (L = PR₃; L-L ≡ dangling polydentate ligand) coupled with ligand and solvent-dependent chemical and homogeneous electron-transfer rates. Reversible oxidation was recognized in the series [RCCo₃(CO)₅(dppm)₂]^2/1/0/1- and [RCCo₃(CO)₆tpme]^1/0/1-. RCCo₃(CO)₇(PPh₃)₂ was obtained by an ETC reaction.