title: Hydroalumination of a chlorotrialkynylsilane: spontaneous stepwise 1,3-dyotropic rearrangement via an intermediate silyl cation.
abstract: A new functionalised alkynylsilane, Cl-Si(CC-CMe3 )3 (3), was obtained by a facile multistep synthesis. Treatment of 3 with equimolar quantities of the hydrides H-M(CMe3 )2 (M=Al, Ga) gave the mixed alkenyl-di(alkynyl)silanes, in which the chlorine atom adopts a bridging position between the aluminium and silicon atoms. Dual hydrogallation of 3 resulted in the formation of a di(alkenyl)-alkynylsilane containing two gallium atoms, one of which is coordinated to the chlorine atom, and the second is bonded to the α-carbon atom of the remaining alkynyl group. A tert-butylsilane was unexpectedly formed by a unique 1,3-dyotropic chlorine-tert-butyl exchange for the corresponding dialuminium compound. One aluminium atom is bonded to a tert-butyl group, a terminal chlorine atom and the α-carbon atom of the ethynyl moiety; the second is coordinatively unsaturated, with two terminal tert-butyl substituents. High-level quantum-chemical calculations favour a stepwise dyotropic rearrangement with an intermediate cationic silicon species over a simultaneous tert-butyl-chlorine migration via a five-coordinate silicon atom in the transition state.
authors.affiliation: Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 30, 48149 Münster (Germany), Fax: (+49) 251-8336660. uhlw@uni-muenster.de.
authors.forename: Werner
authors.initials: W
authors.lastname: Uhl
authors.forename: Jörg
authors.initials: J
authors.lastname: Bohnemann
authors.forename: Marcus
authors.initials: M
authors.lastname: Layh
authors.forename: Ernst-Ulrich
authors.initials: EU
authors.lastname: Würthwein
keywords: alkynes; aluminium; dyotropic rearrangement; hydrometallation; quantum chemistry; silyl cations