SYNTHESIS, LITHIATION AND PREFERRED CONFORMATIONS OF SOME ALPHA-SILYLATED AND ALPHA-STANNYLATED PHOSPHINES

Several phenyl substituted functional methylphosphines bearing a silyl or a stannyl residue in alpha-position, PhP(R)CH2EMe3 1-4, PhP(CH2EMe 3)(2) 5,6, Ph2PCH(SiMe3)(SnMe3) 7, the stannylene-bridged rac/meso-(Ph 2PCHSiMe3)(2)(SnMe2) 8 and the alpha-silylated silylphosphine PhP(SiMe 3)CH2SiMe3 9, are prepared by the reaction of lithio phosphides with h alomethylsilanes and -stannanes. The tin compounds offer an efficient synthetic access to alpha-lithiated phosphines which have a broad pote ntial for the synthesis of alpha- and beta-functional phosphines. Mult inuclear NMR analysis of the silyl-, stannyl- and the mixed silylstann yl derivative indicates preferred conformations with strongly differen t (2)J(P-31,Si-29) and (2)J(Sn-119,P-31), respectively.