Chemistry of strained silicon-containing rings
Subtitle: sila[1]ferrocenophanes and silacyclobutanes.
Published: 2004
Language: eng
Number of pages: 173
Description: Species B and C were investigated as potential models of intermediates in the thermal and/or nucleophilically-assisted ROP of [1]ferrocenophanes. Studies on the polymerization behaviour of D  showed it to have a dramatically increased rate of polymerization over the analogous non-hypercoordinate sila[1]ferrocenophane fcSiMePh ( D). Compound B also exhibited a rate-enhancing effect on the ROP of D and the resultant materials were shown to be copolymeric by characterization of a series of copolymers as well as their corresponding polycationic quaternized derivatives. These studies suggested that hypercoordinate Group 14 centres play a key role in the nucleophilically-assisted ROP of tin-bridged [1]ferrocenophanes and the thermal polymerization of metallocenophanes in the presence of nucleophilic impurities.Incorporation of strained silacyclic rings into catalytic species was investigated as a route to polymer-supported catalysts, with control over the bonding environment of the catalytic moiety dictated by the bonding environment in the monomer. Silacyclobutyl rings were incorporated into the ansa -bridge of zirconocenes to generate the silacyclobutyl-bridged zirconocenophanes (CH2)3SiCp2Zr(NMe2)2 and (CH2)3SiCp2ZrCl2 (A ). Platinum-catalyzed ring-opening polymerization (ROP) of A  yielded the polycarbosilane-supported olefin polymerization catalyst [(CH2)3SiCp2ZrCl2]n.Ring-opening protonolysis of sila[1]ferrocenophanes was investigated as a route to new ferrocenyl-substituted silicon-based species. Addition of HOTf across the Si-Cpipso bond of fcSiMe 2 and fcSiFc2 (Fc = (eta5-C5H 4)Fe(eta5-C5H5)) yielded the covalently bound silyl triflates FcSiMe2OTf and Fc3SiOTf. Reactions with HBF4 yielded the fluorosilanes FcSiMe2F and Fc3SiF and suggested the intermediacy of a highly reactive silylium species, capable of abstracting F- from the tetrafluoroborate anion. Reactions of fcSiMe2, fcSiFc2 and fcSiiPr2 with the acid of the non-coordinating tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anion generated the coordinated silylium ions [FcMe2Si(THF)]+, [Fc 3Si(THF)]+ and [FcSiiPr 2(OEt2)]+. In situ reaction of these species with pyridine generated [FcMe2Si(py)]+ , [Fc3Si(py)]+ and [FcSi iPr2(py)]+, respectively.The first hypercoordinate sila[1]ferrocenophanes fcSiMe(2-C6H 4CH2NMe2) (B) and fcSi(CH 2Cl)(2-C6H4CH2NMe2) ( C) (fc = (eta5-C5H4)2Fe) were synthesized. Structural characterization revealed pseudo-trigonal bipyramidal geometries, with axial positions occupied by nitrogen and one of the Cp ipso carbons. Solution state fluxionality of B and C was indicative of reversible intramolecular coordination of the nitrogen donor group. Quaternization generated [fcSiMe(2-C6H 4CH2NMe3)][OTf] and [fcSi(CH2Cl)(2-C 6H4CH2NMe3)] [OTf], respectively. Compound  C exhibited low room temperature stability and its intramolecular cyclization, to give [fcSi(cyclo-CH2NMe2CH 2C6H4)]Cl, was observed.
Notes: Adviser:  Ian Manners.

Thesis (Ph.D.)--University of Toronto, 2004.

Electronic version licensed for access by U. of T. users.

Source: Dissertation Abstracts International, Volume: 65-10, Section: B, page: 5141.