Tris(pentafluorophenyl)borane as a Superior Catalyst in the Synthesis of Optically Active SiO-Containing Polymers

Tris(pentafluorophenyl)borane was found to be an effective catalyst in the synthesis of optically pure and completely diisotactic phenyl- and naphthyl-substituted poly(siloxane)s by the reaction between (R,R)-1,3-dimethyl-1,3-diphenyl {or di(1-naphthyl)}-1,3-disiloxanediol and 1,1,3,3-tetramethyl-1,3-disiloxane, 1,1,6,6-tetramethyl-1,6-disilahexane, or 1,4-bis(dimethylsilyl)benzene under mild reaction conditions. The optically active disloxane units in the produced polymers had better controlled chemical and stereoregular structures than those obtained from the bis(silanol)s and bis(dimethylamino)dimethylsilane. Homopolymerization of the starting bis(silanol) could be almost completely suppressed. Effects of the structure of the starting bis(silane)s on the yield, molecular weight, optical activity, and thermal properties of the resulting SiOSi-containing polymers were studied.