SYNTHESIS, CHARACTERIZATION, AND POLYMERIZATION OF NEW FERROCENE FLUORENE COMPLEXES - A NOVEL HIGH-MOLECULAR-WEIGHT CONJUGATED POLYMER WITH PENDANT FERROCENE GROUPS

Ferrocenecarboxaldehyde was successfully condensed with fluorene derivatives to afford a series of new complexes, {eta5-C5H5}Fe{eta5-C5H4CH=(9-fluorenyl)} (where fluorenyl = 2-bromo-9-fluorenyl (1a), 2,7-dibromo-9-fluorenyl(2a), 2-nitro-9-fluorenyl(3)). The ferrocene-fluorenyl derivatives 1a and 2a were converted to the formyl, tributylstannyl, diformyl, and bis( tributylstannyl) complexes (1b, 1c, 2b, and 2c, respectively). Complexes 1b and 2b were characterized by single-crystal X-ray molecular structures. The fluorenyl ring systems were tilted out of the eta5-C5H4 plane by 39-degrees. Treatment of 1c and 2c with I2 afforded the mono- and diiodofluorenyl complexes 1d and 2d, respectively. The reactivity of complexes 2a-d was explored. The alkynylation (alkyne, L2PdCl2, CuI, PPh3) of 2a was an extremely poor reaction, giving little or no cross-coupling. Complex 2b did not undergo the Knoevenagel polycondensation with bis(cyanoacetate) comonomers. Treatment of 2c with acid chlorides under Stille cross-coupling conditions afforded ketone product, and iodobenzene showed no cross-coupling. Complex 2d did copolymerize very cleanly with 2,5-diethynyl-1,4-bis(decyloxy)benzene using palladium catalysis to afford a soluble, high-molecular-weight conjugated polymer (4). A model compound (5) was prepared from cross-coupling 1d with 2,5-diethynyl-1,4-bis(decyloxy)benzene. For compound 5 we observed two oxidation events, one at +0.11 V and the other at +0.71 V (relative to the ferrocene/ferrocenium couple). Cyclic voltammetry of polymer 4 showed one, very reversible oxidation event at +0.13 V.