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Título

An alternative mechanistic paradigm for the β-Z hydrosilylation of terminal alkynes: The role of acetone as a silane shuttle

Autor Iglesias, Manuel ; Sanz Miguel, Pablo J. ; Polo, Víctor; Fernández-Álvarez, Francisco J. ; Pérez-Torrente, Jesús J. ; Oro, Luis A.
Palabras clave Silanes
Hydrosilylation
Homogeneous catalysis
Carbenes
Alkynes
Fecha de publicación 2013
EditorWiley-VCH
Citación Chemistry - A European Journal 19(51): 17559-17566 (2013)
ResumenThe β-Z selectivity in the hydrosilylation of terminal alkynes has been hitherto explained by introduction of isomerisation steps in classical mechanisms. DFT calculations and experimental observations on the system [M(I)2{κ-C,C,O,O-(bis-NHC)}]BF4 (M=Ir (3 a), Rh (3 b); bis-NHC=methylenebis(N-2-methoxyethyl)imidazole-2-ylidene) support a new mechanism, alternative to classical postulations, based on an outer-sphere model. Heterolytic splitting of the silane molecule by the metal centre and acetone (solvent) affords a metal hydride and the oxocarbenium ion [R 3Si - O(CH3)2]+, which reacts with the corresponding alkyne in solution to give the silylation product [R 3Si - CHï£C - R]+. Thus, acetone acts as a silane shuttle by transferring the silyl moiety from the silane to the alkyne. Finally, nucleophilic attack of the hydrido ligand over [R3Si - CHï£C - R]+ affords selectively the β-(Z)- vinylsilane. The β-Z selectivity is explained on the grounds of the steric interaction between the silyl moiety and the ligand system resulting from the geometry of the approach that leads to β-(E)-vinylsilanes. Silanes catch the shuttle: An outer-sphere mechanism that explains the β-Z hydrosilylation of terminal alkynes based on the role of acetone as a silane shuttle is disclosed. Heterolytic splitting of the silane molecule by the metal centre and acetone affords a metal hydride and the oxocarbenium ion [R 3Si - O(CH3)2]+, which reacts with the alkyne in solution to give the silylation product [R3Si - CHï£C - R]+ (see figure). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Versión del editorhttp://dx.doi.org/10.1002/chem.201303063
URI http://hdl.handle.net/10261/111096
DOI10.1002/chem.201303063
Identificadoresissn: 0947-6539
e-issn: 1521-3765
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