Facet-Solvent Synergy Enables Stereodivergent Hydrosilylation of Terminal Alkynes Using CsPbBr3 Perovskite Photocatalysts.

Vinylsilanes are indispensable intermediates in modern organic synthesis, yet achieving stereodivergent control in alkyne hydrosilylation remains a long-standing challenge. Herein, we report the first example of visible-light-driven chemodivergent hydrosilylation of terminal alkynes enabled by CsPbBr3 perovskite nanocrystal photocatalysts. By exploiting a unique facet-solvent synergy, the same alkyne substrates can be selectively transformed into either β-(Z)- or β-(E)-vinylsilanes under mild conditions. Dodecahedral CsPbBr3 nanocrystals in nonchlorinated media promote kinetically controlled β-(Z)-selective hydrosilylation with excellent yields and outstanding stereoselectivity (up to E:Z = 1:99). In contrast, cubic CsPbBr3 nanocrystals in chlorinated solvent mixtures undergo halide exchange, enabling time-dependent Z to E isomerization and delivering thermodynamically favored β-(E)-vinylsilanes with remarkable selectivity (up to E:Z = 99:1). Mechanistic investigations support a dual SET/HAT (single-electron transfer/hydrogen atom transfer) photoredox cycle involving silyl radical generation and solvent-induced modulation of perovskite redox properties. The protocol features broad functional group tolerance, gram-scale applicability, catalyst recyclability, and successful late-stage functionalization of natural products and drug derivatives. This work establishes perovskite nanocrystals as versatile photocatalysts for stereodivergent bond construction and highlights solvent-induced halide exchange for catalyst transformation as a powerful strategy in selective photocatalytic synthesis.