Synthesis and redox properties of a pi-conjugated cyclobutadienecobalt polymer containing ferrocenyl groups

The reaction of CpCo( PPh3)(2), in which Cp = eta (5)-cyclopentadienyl with a pi -conjugated diacetylene, FcC dropC-o-C6H4-C drop CFc, in which Fc= fe rrocenyl, was found to give a cyclobutadienecobalt mononuclear complex, {et a (4)-C4Fe2(o-FcC(6)H(4))(2))CoCp (1), the crystal structure of which was d etermined by X-ray crystallography. In contrast, the reaction of CpCo(PPh3) (2) with FcC dropC p-C6H4, C drop CFc affords a cyclobutadienecobalt polyme r, [p-C6H4(eta (4)-C(4)Fc(2)) CoCp](n) (2). The monocobalt complex 1 shows reversible le(-) and 3e(-) redox waves at E-0' = 0.116 and 0.350 V vs Ag/Ag +, and the polymer complex 2 shows two chemically reversible redox waves at E-0' = 0.143 and 0.219 V for the oxidation of the ferrocenyl moieties in t he cyclic voltammogram. Crystal data are as follows: (1. C65H49CoFe4), tric linic, space group P1 (No. 2), a = 13.547(4), b=16.197(4), c = 11.763(4) A, alpha =106.79(2), beta =97.93(3), gamma = 97.12(3), V = 2410(1) A(3), Z = 2.