Photochemical Alkene Hydrophosphination with Bis(trichlorosilyl)phosphine.

Bis(trichlorosilyl)phosphine (HP(SiCl), ) was prepared from [TBA][P(SiCl)] ([TBA], TBA = tetra--butylammonium) and triflic acid in 36% yield. Phosphine is an efficient reagent for hydrophosphination of unactivated terminal olefins under UV irradiation (15-60 min) and gives rise to bis(trichlorosilyl)alkylphosphines (RP(SiCl), R = (CH)CH, 88%; (CH)CH, 98%; (CH)C(CH), 76%; CHCy, 93%; (CH)Cy, 95%; CHCH(CH)(CH)CH, 82%; (CH)O(CH)CH, 95%; (CH)Cl, 83%; (CH)SiMe, 92%; (CH)C(H)CH, 44%) in excellent yields. The products require no further purification beyond filtration and removal of volatile material under reduced pressure. The P-Si bonds of prototypical products RP(SiCl) (R = -(CH)CH, -(CH)CH) are readily functionalized to give further phosphorus-containing products: HC(CH)PCl (56%), [HC(CH)P(CHPh)]Br (84%), HC(CH)PH (61%), HC(CH)P(O)(H)(OH) (81%), and HC(CH)P(O)(OH) (55%). Experimental mechanistic investigations, accompanied by quantum chemical calculations, point toward a radical-chain mechanism. Phosphine enables the fast, high-yielding, and atom-efficient preparation of compounds that contain phosphorus-carbon bonds in procedures that bypass white phosphorus (P), a toxic and high-energy intermediate of the phosphorus industry.