Synthesis and cyclic voltammetric studies of diiron complexes, ER(2)[(eta-C(5)H(4))Fe(L(2))Me](2) (E = C, Si, Ge, Sn; R = H, alkyl; L(2) = diphosphine] and (eta-C(5)H(5))Fe(L(2))ER(2)Fc [Fc = (eta-C(5)H(4))Fe(eta-C(5)H(5))].

The cyclic voltammetric studies on ER(2)[(eta(5)-C(5)H(4))Fe(L(2))Me](2) (L(2) = dppe; ER(2) = CH(2) (1a), SiMe(2) (2a), GeMe(2) (3a), SnMe(2) (4a) revealed two well resolved reversible waves [(1)E(1/2) = -0.33 V, (2)E(1/2) = -0.20 V (for 1a); (1)E(1/2) = -0.35 V, (2)E(1/2) = -0.21 V (for 2a);(1)E(1/2) = -0.36 V, (2)E(1/2) = -0.23 V (for 3a);(1)E(1/2) = -0.36 V, (2)E(1/2) = -0.22 V (for 4a)] in CH(2)Cl(2) suggesting electronic communication between two iron centers which is seen for the first time in this family of organometallic complexes. The resolution between two reversible waves increases in the order of 1a < 2a < 3a < 4a; however, coordinating solvents such as pyridine, PhCN, DMSO and DMF decreased these interactions attributable to the stabilization of cationic species formed after the first oxidation. UV/Vis spectroelectrochemistry of 1a-4a revealed two distinct absorbance patterns for both redox processes and reflected the stepwise oxidation. Homobimetallic complexes containing ferrocenyl groups, (eta(5)-C(5)H(5))Fe(L(2))ER(2)Fc [ER(2) = none, L(2) = cis-dppen (5a), ER(2) = SiMe(2), L(2) = cis-dppen (6a), dppm (6b); ER(2) = GeMe(2), L(2) = cis-dppen (7a), dppm (7b); ER(2) = Sn(t)Bu(2), L(2) = dmpe (8a); Fc = (eta(5)-C(5)H(4))Fe(eta(5)4-C(5)H(5))] were prepared and studied in terms of electrochemistry. The cyclic voltammogram of 5a exhibited two well resolved one electron reversible waves at (1)E(1/2) = -0.21 V and (2)E(1/2) = 0.58 V corresponding to oxidation of the Fe(P-P) and Fc iron atoms respectively. Other complexes in this series (6a/6b, 7a/7b, 8a) containing direct Fe-E-Fc (E = Si, Ge and Sn) bridging units were not stable under electrochemical conditions and rupture of the Fe-E bonds was observed.