Hydroalumination of a Chlorotrialkynylsilane: Spontaneous Stepwise 1,3‐Dyotropic Rearrangement via an Intermediate Silyl Cation |
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| Authors: | Prof. Dr. Werner Uhl Jörg Bohnemann Dr. Marcus Layh Prof. Dr. Ernst‐Ulrich Würthwein |
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| Affiliation: | 1. Institut für Anorganische und Analytische Chemie, Westf?lische Wilhelms‐Universit?t Münster, Corrensstrasse 30, 48149 Münster (Germany), Fax: (+49)?251‐8336660;2. Organisch‐Chemisches Institut, Westf?lische Wilhelms‐Universit?t Münster, Corrensstrasse 36, 48149 Münster (Germany) |
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| 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. |
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| Keywords: | alkynes aluminium dyotropic rearrangement hydrometallation quantum chemistry silyl cations |
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