Synthesis and redox properties of poly(cobaltacyclopentadienylene thienylene)

New poly(cobaltacyclopentadienylene)s with π-conjugated spacers were synthesized by metallacycling polymerization (MCP) using CpCo(PPh3)2 (Cp = η5-cyclopentadienyl) and Me-C=C-A-C=C-Me, where A = phenylene and thienylene, as starting materials. The number-average molecular weights of polymers were 3.8x105 (Mw/Mn = 4.5) and 4.4x103 (Mw/Mn = 1.3), when A = phenylene and thienylene, respectively. Both polymers undergo quasi-reversible oxidation at ca. 0 V vs. Ag/Ag+. The cyclic voltammograms of the polymer with thienylene moiety is broader than that with phenylene moiety, indicating that electronic interaction between the cobalt cites through the thiophene ring is stronger than that through the benzene ring.