ß-(Z) Selectivity Control by Cyclometalated Rhodium(III)-Triazolylidene Homogeneous and Heterogeneous Terminal Alkyne Hydrosilylation Catalysts

Sánchez-Page, B. ; Munarriz, J. ; Jiménez, M.V. (Universidad de Zaragoza) ; Pérez-Torrente, J.J. (Universidad de Zaragoza) ; Blasco, J. (Universidad de Zaragoza) ; Subias, G. ; Passarelli, V. (Universidad de Zaragoza) ; Álvarez, P.

Resumen: The cyclometalated Rh(III)-NHC compounds [Cp*RhI(C, C')-Triaz] (Triaz = 1, 4-diphenyl-3-methyl-1, 2, 3-triazol-5-ylidene) and [Cp*RhI(C, C')-Im] (Im = 1-phenyl-3-methyl-imidazol-2-ylidene) are efficient catalysts for the hydrosilylation of terminal alkynes with complete regio- and stereoselectivity toward the thermodynamically less stable ß-(Z)-vinylsilane isomer at room temperature in chloroform or acetone. Catalyst [Cp*RhI(C, C')-Triaz] shows a superior catalytic performance in terms of activity and has been applied to the hydrosilylation of a range of linear 1-alkynes and phenylacetylene derivatives with diverse hydrosilanes, including HSiMePh2, HSiMe2Ph, HSiEt3, and the bulkier heptamethylhydrotrisiloxane (HMTS), to afford the corresponding ß-(Z)-vinylsilanes in quantitative yields. The graphene-based hybrid material TRGO-Triaz-Rh(III), featuring cyclometalated [Cp*RhI(C, C')-Triaz] (Triaz = 1, 4-diphenyl-3-methyl-1, 2, 3-triazol-5-ylidene) rhodium(III) complexes covalently immobilized through the triazolylidene linker, has been prepared by metalation of the trimethylsilyl-protected 3-methyl-4-phenyl-1, 2, 3-triazolium iodide functionalized graphene oxide material, TRGO-Triaz, with [Cp*RhCl2]2 using sodium tert-butoxide as base. The coordination sphere of the supported rhodium(III) complexes has been determined by means of XPS and extended X-ray absorption fine structure (EXAFS) spectroscopy, showing the replacement of the iodido ligand by O-functionalities on the carbon wall. In sharp contrast with the homogeneous catalyst, the heterogeneous hybrid catalyst TRGO-Triaz-Rh(III) is not active at room temperature although it shows an excellent catalytic performance at 60 °C. In addition, the hybrid catalyst TRGO-Triaz-Rh(III) has shown an excellent recyclability, allowing at least six catalytic runs in the hydrosilylation of oct-1-yne with HSiMePh2 in acetone with complete selectivity to the ß-(Z)-vinylsilane product. The reaction mechanism for the molecular catalyst [Cp*RhI(C, C')-Triaz] has been explored by means of DFT calculations, pointing to a metal-ligand bifunctional mechanism involving reversible cyclometalation that is competitive with a noncooperative pathway. The proposed mechanism entails the Rh-CAr assisted hydrosilane activation to afford a reactive Rh-silyl intermediate that leads to a (E)-silylvinylene intermediate after alkyne insertion and a metallacyclopropene-driven isomerization. The release of the ß-(Z)-vinylsilane product can occur by a reversible cyclometalation mechanism involving s-CAM with the CAr-H bond or, alternatively, the Si-H bond of an external hydrosilane. The energy barrier for the latter is 1.2 kcal·mol-1 lower than that of the CAr-H bond, which results in a small energy span difference that makes both pathways competitive under catalytic conditions.

Idioma: Inglés

DOI: 10.1021/acscatal.0c03295

Año: 2020

Publicado en: ACS CATALYSIS 10, 22 (2020), 13334-13351
ISSN: 2155-5435

Factor impacto JCR: 13.084 (2020)

Categ. JCR: CHEMISTRY, PHYSICAL rank: 15 / 162 = 0.093 (2020) - Q1 - T1

Factor impacto SCIMAGO: 4.897 - Chemistry (miscellaneous) (Q1) - Catalysis (Q1)

Financiación: info:eu-repo/grantAgreement/ES/DGA-FSE/E12-20R
Financiación: info:eu-repo/grantAgreement/ES/DGA-FSE/E42-20R
Financiación: info:eu-repo/grantAgreement/ES/MICINN-FEDER/CTQ2016-75884-P
Financiación: info:eu-repo/grantAgreement/ES/MICINN-FEDER/PID2019-103965GB-I00
Financiación: info:eu-repo/grantAgreement/ES/MICINN-FEDER/RTI2018-098537-B-C22

Tipo y forma: Article (PostPrint)

Área (Departamento): Área Química Inorgánica (Dpto. Química Inorgánica)
Área (Departamento): Área Física Materia Condensada (Dpto. Física Materia Condensa.)