SYNTHESIS AND PROPERTIES OF POLY(FERROCENYLDIHYDROSILANE) HOMOPOLYMER AND RANDOM COPOLYMERS

The strained, silicon-bridged [1]ferrocenophane Fe(eta-C5H4)(2)SiH2 (4) was prepared via the reaction of H2SiCl2 with Fe(eta-C5H4Li)2 . TMEDA in ether at < -78 degrees C. This species was analyzed by single-crystal X-ray diffraction and was found to possess a strained, ring-tilted structure similar to those of previously reported silicon-bridged [1]ferrocenophanes [tilt angle 19.1(1)degrees]. Thermal ring-opening polymerization of 4 afforded the poly(ferrocenylsilane) [Fe(eta-C5H4)(2)SiH2](n) (5), which was found to be insoluble in common organic solvents. Under the same conditions, mixtures of 4 and the dimethyl analog Fe(eta-C5H4)(2)SiMe(2) (1a) afforded soluble copolymers 7a-c, consisting of random ferrocenyldihydrosilane and ferrocenyldimethylsilane repeat units, as the first examples of poly(ferrocenylsilane) copolymers prepared via ring-opening polymerization. Repeat unit composition of the random copolymers could be controlled by manipulation of the monomer ratio and was readily assessed by H-1 NMR spectroscopy. TGA of 5 under N-2 at a heating rate of 10 degrees C/min found this material to be the most thermally stable to weight loss of all the poly(ferrocenylsilanes) yet studied with only 10% weight loss up to 600 degrees C and a ceramic yield of 63% at 1000 degrees C. Among copolymers 7a-c, thermal stability to weight loss increased with increasing ferrocenyldihydrosilane repeat unit content. The homopolymer 5 was found to be crystalline by wide-angle X-ray scattering, and a melting transition at 165 degrees C was detected by DSC. Glass transitions for the essentially amorphous copolymers were observed to fall between the T-g of 18 degrees C observed for 5 and the T-g of 33 degrees C reported for [Fe(eta-C5H4)(2)SiMe(2)](n) (2a).