Rh(I)/(III)‐N‐Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio‐ and Stereoselectivity in the Hydrosilylation of Alkynes

P.K.R. Panyam, B. Atwi, F. Ziegler, W. Frey, M. Nowakowski, M. Bauer, M.R. Buchmeiser, Chemistry – A European Journal 27 (2021) 17220–17229.

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Journal Article | Published | English
Author
Panyam, Pradeep K. R.; Atwi, Boshra; Ziegler, Felix; Frey, Wolfgang; Nowakowski, MichałLibreCat ; Bauer, MatthiasLibreCat ; Buchmeiser, Michael R.
Abstract
Rh(I) NHC and Rh(III) Cp* NHC complexes (Cp*=pentamethylcyclopentadienyl, NHC=N-heterocyclic carbene=pyrid-2-ylimidazol-2-ylidene (Py−Im), thiophen-2-ylimidazol-2-ylidene) are presented. Selected catalysts were selectively immobilized inside the mesopores of SBA-15 with average pore diameters of 5.0 and 6.2 nm. Together with their homogenous progenitors, the immobilized catalysts were used in the hydrosilylation of terminal alkynes. For aromatic alkynes, both the neutral and cationic Rh(I) complexes showed excellent reactivity with exclusive formation of the β(E)-isomer. For aliphatic alkynes, however, selectivity of the Rh(I) complexes was low. By contrast, the neutral and cationic Rh(III) Cp* NHC complexes proved to be highly regio- and stereoselective catalysts, allowing for the formation of the thermodynamically less stable β-(Z)-vinylsilane isomers at room temperature. Notably, the SBA-15 immobilized Rh(I) catalysts, in which the pore walls provide an additional confinement, showed excellent β-(Z)-selectivity in the hydrosilylation of aliphatic alkynes, too. Also, in the case of 4-aminophenylacetylene, selective formation of the β(Z)-isomer was observed with a neutral SBA-15 supported Rh(III) Cp* NHC complex but not with its homogenous counterpart. These are the first examples of high β(Z)-selectivity in the hydrosilylation of alkynes by confinement generated upon immobilization inside mesoporous silica.
Publishing Year
Journal Title
Chemistry – A European Journal
Volume
27
Issue
68
Page
17220-17229
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Panyam PKR, Atwi B, Ziegler F, et al. Rh(I)/(III)‐N‐Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio‐ and Stereoselectivity in the Hydrosilylation of Alkynes. Chemistry – A European Journal. 2021;27(68):17220-17229. doi:10.1002/chem.202103099
Panyam, P. K. R., Atwi, B., Ziegler, F., Frey, W., Nowakowski, M., Bauer, M., & Buchmeiser, M. R. (2021). Rh(I)/(III)‐N‐Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio‐ and Stereoselectivity in the Hydrosilylation of Alkynes. Chemistry – A European Journal, 27(68), 17220–17229. https://doi.org/10.1002/chem.202103099
@article{Panyam_Atwi_Ziegler_Frey_Nowakowski_Bauer_Buchmeiser_2021, title={Rh(I)/(III)‐N‐Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio‐ and Stereoselectivity in the Hydrosilylation of Alkynes}, volume={27}, DOI={10.1002/chem.202103099}, number={68}, journal={Chemistry – A European Journal}, publisher={Wiley}, author={Panyam, Pradeep K. R. and Atwi, Boshra and Ziegler, Felix and Frey, Wolfgang and Nowakowski, Michał and Bauer, Matthias and Buchmeiser, Michael R.}, year={2021}, pages={17220–17229} }
Panyam, Pradeep K. R., Boshra Atwi, Felix Ziegler, Wolfgang Frey, Michał Nowakowski, Matthias Bauer, and Michael R. Buchmeiser. “Rh(I)/(III)‐N‐Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio‐ and Stereoselectivity in the Hydrosilylation of Alkynes.” Chemistry – A European Journal 27, no. 68 (2021): 17220–29. https://doi.org/10.1002/chem.202103099.
P. K. R. Panyam et al., “Rh(I)/(III)‐N‐Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio‐ and Stereoselectivity in the Hydrosilylation of Alkynes,” Chemistry – A European Journal, vol. 27, no. 68, pp. 17220–17229, 2021, doi: 10.1002/chem.202103099.
Panyam, Pradeep K. R., et al. “Rh(I)/(III)‐N‐Heterocyclic Carbene Complexes: Effect of Steric Confinement Upon Immobilization on Regio‐ and Stereoselectivity in the Hydrosilylation of Alkynes.” Chemistry – A European Journal, vol. 27, no. 68, Wiley, 2021, pp. 17220–29, doi:10.1002/chem.202103099.

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