Cyclopentadienyl cobalt complexes (n5-C5H4R)CoLI2 [L = CO,R=-COOCH2CH=CH2 (3); L=PPh3,R=-COOCH2-CH=CH2 (6); L= P(p-C6H4CH3)3,R=-COOC(CH3) = CH2 (7),-COOCH2C6H5(8),-COOCH2CH = CH2 (9)] were prepared and characterized by elemental analyses,1H NMR,IR and UV-vis spectra.The reaction of complexes (n5-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 (n5-C5H4R)2Co [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 α,α’-substituted cobaltocene showed reversible oxidation of one electron pro- L = P (p-C6H4CH3) 3, where R = -COOCH2CH = CH2 (3); L = R = -COOC (CH3) = CH2 (7), - COOCH2C6H5 (8), - COOCH2CH = CH2 (9)] were prepared and characterized by elemental analyzes, 1H NMR, IR and UV-vis spectra. The reaction of complexes (2): L = PPh3, R = -COOC (CH3) = CH2 (4), - COOCH2C6H5 (5) )] with Na-Hg resulted in the formation of their corresponding substituted cobaltocene (n5-C5H4R) 2Co [R = -COOC (CH3) = CH2 (10), - COOCH2C6H5 11 were studied by cyclic voltammetry. It was found that as ligand (L) of the cobalt (III) complexes changing from CO to PPh3 and P (p-tolyl) 3, their oxidation potentials were gradually increased. The cyclic voltammetry of α, α’-substituted cobaltocene showed reversible oxidation of one electron pro-