ORGANOMETALLIC NONLINEAR OPTICAL POLYMERS .3. COPOLYMERIZATION OF BRIDGED BIS(FERROCENYL) AND BIS(CYANOACETATE) MONOMERS VIA THE KNOEVENAGEL CONDENSATION

The bridged bis(ferrocenyl) monomer [{eta5-C5H4CHO}Fe{eta5-C5H4}]2SiMe2 (1) was prepared in two steps from {eta5-C5H4SnBu3}2Fe. A single-crystal molecular structure was obtained for monomer 1. The bis(cyanoacetate) monomers CNCH2CO2(CH2)nO2CCH2CN (2) [where n = 4,6, and 81 were prepared in high yield by reacting ethyl cyanoacetate with the appropriate diol in the presence of Ti(OC4H9)4. Knoevenagel polycondensation [K2CO3, THF, 50-degrees-C] of 1 and 2 afforded a new class of organometallic accordion copolymers. Average molecular weights for the accordion copolymers ranged from 9100 to 26 600 with polydispersities of approximately 2.1. The polymers were soluble in organic solvents and thus fully characterized by spectroscopic methods. The polymers were also characterized by thermal analysis and analytical data. The Knoevenagel polycondensation reaction appeared to produce a mixture of E and Z isomers (9/1, respectively); however, isomerically enriched polymer (i.e., 98% E isomer) was obtained through selective precipitation.