Frustrated Lewis Pair Route to Hydrodesilylation of Silylphosphines

A 1:1 mixture of P­(SiMe3)3 and B­(p-C6F4H)3 reacts with 3 equiv of 4-heptanone to afford a 1:2 mixture of [(Me3SiO)­(n-Pr)2C]­H2P–B­(p-C6F4H)3 and the silyl enol ether, 4-trimethylsiloxy-3-heptene. Subsequent thermolysis of the adduct produces H3P–B­(p-C6F4H)3 and an additional equiv of silyl enol ether. In the presence of a catalytic quantity of B­(p-C6F4H)3, however, P­(SiMe3)3 reacts with 4-heptanone to produce a 1:1 mixture of [(Me3SiO)­(n-Pr)2C]2PH and silyl enol ether. Heating this mixture further produces [(Me3SiO)­(n-Pr)2C]­PH2, which is eventually converted to elemental phosphorus.