Synthesis and characterization of a free phenylene bis(N-heterocyclic carbene) and its di-Rh complex: Catalytic activity of the di-Rh and CCC–NHC Rh pincer complexes in intermolecular hydrosilylation of alkynes |
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| Institution: | 1. Institut de Physique et Chimie des Matériaux de Strasbourg, Université de Strasbourg-CNRS UMR 7504, 23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2, France;2. Service de Radiocristallographie, Institut de Chimie CNRS – Université de Strasbourg, 1, rue Blaise Pascal, 67070 Strasbourg, France;3. University of Strasbourg Institute for Advanced Study (USIAS), 5 allée du Général Rouvillois, 67083 Strasbourg, France;1. Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari, Venice, Italy;2. Dipartimento di Chimica e Centro di Strutturistica Diffrattometrica, Università di Ferrara, Ferrara, Italy;1. Laboratory of Organometallics, Catalysis and Ordered Materials, State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Center for Chemical and Material Engineering, Wuhan University of Technology, Wuhan, China;2. Department of Applied Chemistry, Faculty of Sciences, Wuhan University of Technology, Wuhan 430070, China;3. Tomsk Polytechnic University, Lenin Avenue 30, 634050 Tomsk, Russian Federation;4. Chemistry Department, Faculty of Science, Fayoum University, Fayoum 63514, Egypt;5. Ghent University, Global Campus Songdo, 119 Songdomunhwa-Ro, Yeonsu-Gu, Incheon, South Korea |
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| Abstract: | 1,3-Bis(3-butylimidazolium-1-yl)benzene diiodide (1) was reacted with Li(2,2,6,6-tetramethylpiperidine) yielding the free bis-carbene, 1,3-bis(3-butylimidazol-2-ylidene-1-yl)benzene (3), which has been spectroscopically characterized. Combining the free bis-carbene with Rh(COD)Cl]2 yielded the corresponding di-Rh bis(N-heterocyclic carbene) complex (4) that was structurally characterized. The di-Rh bis-carbene complex was found to exhibit complex solution 13C and 1H NMR spectra that have been assigned as a mixture of diastereomers. The crystal structure of the di-Rh bis-carbene compound 4 was composed of a pair of enantiomeric atropisomers. The diastereomeric atropisomers were assigned as the source of the spectral complexities. The di-Rh di-carbene complex 4 and the CCC–NHC Rh pincer complex 2 were applied as catalysts in hydrosilylation reactions of terminal and internal alkynes. Both catalysts are highly active, regioselective, stereoselective, and chemoselective: terminal alkynes give predominantly the β-(Z) isomer and internal alkynes afford the β-(E) isomer in chloroform or benzene. One of the strongest attributes of the catalyst systems is that the results were achieved without exclusion of air and without purification of commercially available reagents. |
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