Some [tris(trimethylsilyl)methyl]phosphorus derivatives
Abstract
Treatment of Li[C(SiMe3)3] with PPh2Cl gave the phosphine P[C(SiMe3)3]Ph2, which, in spite of the steric crowding caused by the silicon ligand, was readily converted into the phosphonium salts [P{C(SiMe3)3}Ph2H]I and [P{C(SiMe3)3}Ph2Me]I; the latter on heating gave the ylid MePh2PC(SiMe3)2. In methanol at room temperature the phosphine P[C(SiMe3)3]Ph2 readily loses one Me3Si group to give P[CH(SiMe3)2]Ph2; the remaining Me3Si groups are lost successively, with decreasing ease, giving finally PPh2Me. These Si–C bond cleavages are catalysed by acid but inhibited by base, and it is suggested that the initial step is protonation of the phosphine. The quaternary salt [P{C(SiMe3)3}Ph2Me]I successively loses its Me3Si groups very readily in methanol, ultimately to give [PPh2Me2]I.