The Unexpected Mechanism Underlying the High‐Valent Mono‐Oxo‐Rhenium(V) Hydride Catalyzed Hydrosilylation of CN Functionalities: Insights from a DFT Study |
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| Authors: | Liangfang Huang Prof Xiaodi Yang Prof Haiyan Wei |
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| Affiliation: | Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, Jiangsu Provincial Key Laboratory for NSLSCS, Nanjing Normal University, Nanjing 210097 (China) |
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| Abstract: | In this study, we theoretically investigated the mechanism underlying the high‐valent mono‐oxo‐rhenium(V) hydride Re(O)HCl2(PPh3)2 ( 1 ) catalyzed hydrosilylation of C?N functionalities. Our results suggest that an ionic SN2‐Si outer‐sphere pathway involving the heterolytic cleavage of the Si?H bond competes with the hydride pathway involving the C?N bond inserted into the Re?H bond for the rhenium hydride ( 1 ) catalyzed hydrosilylation of the less steric C?N functionalities (phenylmethanimine, PhCH=NH, and N‐phenylbenzylideneimine, PhCH=NPh). The rate‐determining free‐energy barriers for the ionic outer‐sphere pathway are calculated to be ～28.1 and 27.6 kcal mol?1, respectively. These values are slightly more favorable than those obtained for the hydride pathway (by ～1–3 kcal mol?1), whereas for the large steric C?N functionality of N,1,1‐tri(phenyl)methanimine (PhCPh=NPh), the ionic outer‐sphere pathway (33.1 kcal mol?1) is more favorable than the hydride pathway by as much as 11.5 kcal mol?1. Along the ionic outer‐sphere pathway, neither the multiply bonded oxo ligand nor the inherent hydride moiety participate in the activation of the Si?H bond. |
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| Keywords: | density functional theory catalysis hydrosilylation mechanism rhenium |
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