DIPEA-induced Si–H activation of siloxane for hydrosilylation polymerization via metal-free photocatalysis†

Abstract

Although metal-free hydrosilylation of siloxanes is essential for the industrial preparation of organosilicon compounds due to its unique advantages, such as the avoidance of the use and residue of precious metals, efficient metal-free silicon hydrogenation reactions are still rare. Herein, we report a straightforward visible light-driven metal-free hydrosilylation reaction based on siloxanes and silicon vinyl groups, catalyzed by the synergistic effect of the organic photooxidation catalyst 2,4,6-tris(diphenylamino)-5-fluoroisophthalonitrile and the base N,N′-diisopropylethylamine, which undergo electron transfer and selectively induce Si–H activation during catalysis. After optimization, the silicon vinyl conversion rate in the hydrosilylation reaction exceeded 99% without using any traditional hydrogen atom transfer reagents. Mechanistic studies based on experimental data and theoretical calculations revealed that the reaction proceeds through a free radical reaction and is thermodynamically feasible. The proposed methodology efficiently affords linear polymer formation via a stepwise growth approach. Furthermore, it can crosslink commercial high-molecular-weight polyvinyl silicone oil with disiloxane, realizing the gelation of the material.