Si–H Bond Activation with Bullock’s Cationic Tungsten(II) Catalyst: CO as Cooperating Ligand
Open Access
- 6 November 2019
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 141 (47), 18845-18850
- https://doi.org/10.1021/jacs.9b10304
Abstract
An in-depth investigation of the reaction of tertiary hydrosilanes with [CpW(CO)2(IMes)]+[B(C6F5)4]- reveals a fundamentally new Si-H bond activation mode. Unlike the originally proposed oxidative addition of the Si-H bond to the tungsten(II) center, there is strong experimental and NMR spectroscopic evidence for the involvement of one of the CO ligands of the cationic complex in the Si-H bond breaking event. The Si-H bond is heterolytically cleaved to form a tungsten(II) hydride and a silylium ion, which is stabilized by one of the CO ligands. This reactive hydrosilane adduct was eventually isolated and characterized by X-ray diffraction analysis. Quantum-chemical calculations support a cooperative mechanism but a stepwise process consisting of oxidative addition and subsequent tungsten-to-oxygen silyl migration in the tungsten(IV) silyl hydride is also energetically feasible. However, our combined spectroscopic and computational analysis favors the cooperative pathway. The newly identified hydrosilane adduct is the key intermediate of Bullock's ionic carbonyl hydrosilylation.Funding Information
- Vedeck? Grantov? Agent?ra M?VVa? SR a SAV (1/0507/17, 1/0712/18)
- Deutsche Forschungsgemeinschaft (Oe 249/20-1)
- H2020 Marie Sklodowska-Curie Actions (752285)
- Einstein Stiftung Berlin
- Verband der Chemischen Industrie
- Agent?ra na Podporu V?skumu a V?voja (APVV-17-0324)
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