Synthesis, reactivity and electrochemical properties of substituted cyclopentadienyl cobalt(III) complexes

Cyclopentadienyl cobalt complexes (eta(5)-C5H4R)CoLI2 [L = CO, R = -COOCH2CH = CH2 (3); L = PPh3, R = -COOCH2CH = CH2 (6); L = P(p-C6H4CH3)(3), R = -COOC(CH3) = CH2 (7), -COOCH2C6H5 (8), -COOCH2CH = CH2 (9)] were prepared and characterized by elemental analyses, H-1 NMR, IR and UV-vis spectra. The reaction of complexes (eta(5)-C5H4R)CoLI2 [L = CO, R= -COOC(CH3) = CH2 (1), -COOCH2C6H5 (2); L = PPh3, R = -COOC(CH3) = CH2 (4), -COOCH2C6H5 (5)] with Na-Hg resulted in the formation of their corresponding substituted cobaltocene (eta(5)-C5H4R)(2)Co [R = -COOC(CH3) = CH2 (10), -COOCH2C6H5 (11)]. The electrochemical properties of these complexes 1-11 were studied by cyclic voltammetry. It was found that as the ligand (L) of the cobalt (III) complexes changing from co to PPH3 and P(p-tolyl)(3), their oxidation potentials increased gradually. The cyclic voltammetry of alpha,alpha'-substituted cobaltocene showed reversible oxidation of one electron process.