title: Synthesis of ansa-[n]silacyclopentadienyl-cycloheptatrienyl-chromium complexes (n = 1, 2): novel precursors for polymers bearing chromium in the backbone.
abstract: Reaction of [(eta5-C5H4Li)(eta7-C7H6Li)Cr]tmeda with a variety of dialkyl(dichloro)silanes in aliphatic solvents afforded the corresponding [1]silatrochrocenophanes. Structural characterization by X-ray diffraction analysis of the [1]silatrochrocenophanes bearing Me2Si, (iPr)2Si, and silacyclobutane bridges revealed tilt angles alpha of 15.56(12) degrees , 15.8(1) degrees , and 16.33(17) degrees , respectively. Analogously, a [2]silatrochrocenophane (6) was prepared in excellent yield by reaction of [(eta5-C5H4Li)(eta7-C7H6Li)Cr]tmeda with 1,2-dichloro-1,1,2,2-tetramethyldisilane. This complex also was characterized structurally and exhibited a tilt angle alpha of 2.60(15) degrees. The [1]silatrochrocenophane bearing the Me2Si bridge underwent facile and regioselective carbon-silicon bond cleavage with [Pt(PEt3)4] to give a very high yield of an oxidative addition product. The ring-opening polymerization of these novel [1]silatrochrocenophanes afforded ring-opened chromium-based polymers.
authors.affiliation: Inorganic Rings and Macromolecules, Dept. of Chemistry, 80 St. George St., Toronto, Ontario M5S 3H6, Canada.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Bartole-Scott
authors.forename: Holger
authors.initials: H
authors.lastname: Braunschweig
authors.forename: Thomas
authors.initials: T
authors.lastname: Kupfer
authors.forename: Matthias
authors.initials: M
authors.lastname: Lutz
authors.forename: Ian
authors.initials: I
authors.lastname: Manners
authors.forename: Thi-Loan
authors.initials: TL
authors.lastname: Nguyen
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Radacki
authors.forename: Fabian
authors.initials: F
authors.lastname: Seeler