108452-84-2Relevant articles and documents
Cobaltacycles in three oxidation states: Redox properties and reaction routes
Kelly, Richard S.,Geiger, William E.
, p. 1432 - 1439 (1987)
The electrochemical reduction and oxidation of the Co(III) metallacycle Cp(PPh3)CoC4Ph4 (1) and its analogues have been studied. Oxidation is reversible (E° = +0.35 V vs. SCE) in dichloromethane to give a persistent cation radical which was characterized by ESR spectroscopy. A second oxidation (E° = +1.17 V) gives a more reactive dication which ultimately decomposes by disruption of the metallacycle. Reduction goes by fast one-electron transfer to a 19-electron complex which rapidly loses phosphine to give a transient 17-electron coordinatively unsaturated anion. In the presence of phosphines PR3 which are more basic than PPh3, efficient substitution of PPh3 by PR3 accompanies the reduction, in a partially electrocatalytic process. In the absence of added ligands, the 17-electron anion undergoes protonation and subsequent reduction via a ECEC mechanism to give a π-butadiene complex. The electrochemical results are interpreted in terms of previously published molecular orbital calculations on this class of molecules.
