Synthesis characterization, and the platinum-catalyzed ring-opening polymerization and stereoselective dimerization of silicon-bridged [1]ferrocenophanes with acetylenic substituents

Reaction of the lithium acetylides LiCdropCR (R = Ph, nBu) with the silicon-bridged [1]ferrocenophane Fe(eta-C5H4)(2)Si(Me)Cl (2a) at -78 degreesC was found to result in selective substitution of Cl., forming sila[1]ferrocenophanes with acetylenic substituentg Fe(eta-C5H4)(2)- Si(Me)CdropCR (4, R = Ph; 5, R = nBu). A similar reaction of sila[1]ferrocenophane Fe(eta-C5H4)(2)SiCl2 (2b) with 2 equiv of LiCdropCPh resulted in the substitution of both Cl atoms, forming Fe(eta-C5H4)(2)Si(CdropCPh)(2) (6). Transition metal-catalyzed ring-opening polymerization of monomers 4, 5, and 6 resulted in the formation of high molecular weight (M-n > 10(4)-10(5)) polyferrocenylsilanes with acetylenic substituents, [Fe(eta-C5H4)(2)Si(Me)CdropCR](n) (7, R = Ph; 8, R = nBu) and [Fe(eta-C5H4)(2)Si(CdropCPh)(2)](n) (9), respectively. The cyclic dimer [Fe(eta-C5H4)(2)Si(Me)CdropCPh](2) (10) Was isolated from the polymerization mixture derived from 4. The dimer was shown to exist in the cis configuration by single-crystal X-ray diffraction. Detailed studies on the polymerization of 4 have shown that the ratio of high polymer 7 to cyclic dimer 10 formed in the reaction is highly solvent and concentration dependent. Pyrolysis of polymers, 7 and 8 during thermogravimetric analysis (TGA) studies have resulted in the formation of black magnetic ceramics in the highest yields found to date for uncrosslinked polyferrocenylsilane homopolymers (2 h, 900 degreesC; 7, 81%; 8, 61%).