Hydrosilylation of terminal alkynes catalyzed by a ONO-pincer iridium(III) hydride compound: Mechanistic insights into the hydrosilylation and dehydrogenative silylation catalysis
| Autor: | Duc Hanh Nguyen, Raquel Puerta-Oteo, Daniel Gómez-Bautista, Jesús J. Pérez-Torrente, M. Victoria Jiménez, Manuel Iglesias, F. Javier Modrego, Luis A. Oro |
|---|---|
| Přispěvatelé: | Ministerio de Economía y Competitividad (España), European Commission, Diputación General de Aragón |
| Rok vydání: | 2016 |
| Předmět: |
chemistry.chemical_classification
Denticity 010405 organic chemistry Alkene Hydride Hydrosilylation Organic Chemistry 010402 general chemistry 01 natural sciences Medicinal chemistry 0104 chemical sciences Pincer movement Inorganic Chemistry chemistry.chemical_compound chemistry Pyridine Organic chemistry Physical and Theoretical Chemistry Selectivity Pincer ligand |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| ISSN: | 1520-6041 0276-7333 |
| Popis: | The catalytic activity in the hydrosilylation of terminal alkynes by the unsaturated hydrido iridium(III) compound [IrH(κ-hqca)(coe)] (1), which contains the rigid asymmetrical dianionic ONO pincer ligand 8-oxidoquinoline-2-carboxylate, has been studied. A range of aliphatic and aromatic 1-alkynes has been efficiently reduced using various hydrosilanes. Hydrosilylation of the linear 1-alkynes hex-1-yne and oct-1-yne gives a good selectivity toward the β-(Z)-vinylsilane product, while for the bulkier t-Bu-C≡CH a reverse selectivity toward the β-(E)-vinylsilane and significant amounts of alkene, from a competitive dehydrogenative silylation, has been observed. Compound 1, unreactive toward silanes, reacts with a range of terminal alkynes RC≡CH, affording the unsaturated η-alkenyl complexes [Ir(κ-hqca)(E-CH=CHR)(coe)] in good yield. These species are able to coordinate monodentate neutral ligands such as PPh and pyridine, or CO in a reversible way, to yield octahedral derivatives. Further mechanistic aspects of the hydrosilylation process have been studied by DFT calculations. The catalytic cycle passes through Ir(III) species with an iridacyclopropene (η-vinylsilane) complex as the key intermediate. It has been found that this species may lead both to the dehydrogenative silylation products, via a β-elimination process, and to a hydrosilylation cycle. The β-elimination path has a higher activation energy than hydrosilylation. On the other hand, the selectivity to the vinylsilane hydrosilylation products can be accounted for by the different activation energies involved in the attack of a silane molecule at two different faces of the iridacyclopropene ring to give η-vinylsilane complexes with either an E or Z configuration. Finally, proton transfer from a η-silane to a η-vinylsilane ligand results in the formation of the corresponding β-(Z)- and β-(E)-vinylsilane isomers, respectively. Financial support from the Ministerio de Economia y Competitividad (MINECO/FEDER) of Spain (Project CTQ2013-42532-P) and Diputación General de Aragón (DGA/FSE E07) is gratefully acknowledged. R.P.-O. acknowledges her fellowship from the MINECO (BES-2011-045364). |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|