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.