Photoinduced hydrosilylation through hydrogen abstraction: an NMR and computational study of the structural effect of silane

The hydrosilylation reaction, describing the addition of Si-H bonds to unsaturated bonds, is performed in the presence of catalysts, usually highly active platinum catalysts. This work focuses on the study of a photoinduced hydrosilylation by the use of benzophenone which promotes the addition reaction of olefin on different hydrosilanes. The reactivity of silanes towards addition onto the double bond during hydrosilylation appears to depend on their structure. It was observed that the consumption of Si-H and C=C functional groups increases with the irradiation time, and reaches a maximum of approx. 51% in the case of diphenykilane. The hydrosilylation products are determined with H-1 NMR, HSQC, DEPT, COSY and C-13 NMR. The main product corresponds to the single adduct of the silyl radical onto the double bond. Substitution of the Si-H bond by two or three phenyls groups (triphenykilane, diphenysilane) enhances the yield of the reaction, although diphenykilane was found to be more efficient than triphenykilane because of its Lower steric hindrance. The ketyl radical formed after hydrogen abstraction by the triplet state of benzophenone likely forms benzopinacol, a reaction which reduces the overall yield of the hydrosilylation reaction. ALL these experiments are in Line with DFT calculations of the Gibbs free energy of the reactions involved. This sheds new Light on the photoinduced hydrosilylation process and opens the way to more active combinations of photoinitiator/silane/vinykilane systems.

Automated summary

The study investigates the photoinduced hydrosilylation reaction using benzophenone as a photoinitiator. The reactivity of different hydrosilanes towards addition onto the double bond is found to depend on their structure. Various spectroscopic techniques were used to determine the reaction products, and it was observed that the substitution of the Si-H bond by phenyl groups can enhance the reaction yield.