Silylphosphines acidity

Silylphosphines, (R3Si)3P, are well known. On the basis of electronegativity (Table 1) they are weaker n acids than organophosphines. With the isolation of R2Si=PR compounds, an increased variety of structmes is available. Six-membered silicon-phosphorus heterocycles (1) have been proposed as ligands for catalyst candidates, owing to the steric accessibility of the transition metal. 

The reactions of silylphosphines with electron-rich compounds are complex, involving insertion into the Si-P bond as the first step. With carbon dioxide, bis(silyl)phosphines give an equilibrium (equation 20) dominated by the phosphacarbamic acid ester 8 which loses disiloxane if R = 2,4,6-t-Bu3C6H2 (henceforth represented as Ar) to give the phosphaketene 9. This in turn reacts with the silylphosphide 10 to form the 1,3-phosphaallene 11, an analogue of carbodiimides, and also results directly from ArPHSiMe3, n-BuLi and C02 (equation 21)28. 

Lewis-acid-catalyzed/mediated Phosphination. The silylphosphine smoothly reacted with electrophiles activated by a Lewis acid. Addition of the silylphosphine to the activated pro-piolates also proceeded to produce vicinal s yn-silylphosphinated acrylates (eq 5). ... 

In the presence of Lewis acids such as EtsAl, EtaAlCl, and BF3 OEt2, the silylphosphine reacted with aldehydes and epoxides to give the corresponding a- and /3-hydroxyalkylphosphine derivatives, respectively (eqs 6 and 7)5 The more substituted alkylphosphine was preferentially formed by using an unsymmetrical epoxide. This is in contrast to the basic phosphination of epoxides, which provides mainly less substituted alkylphosphines. ... 

Silylation of Alcohols. The silylphosphine serves as a silyl group source for the silylation of alcohols in the presence of DEAD and PPTS. Primary and secondary hydroxy groups are rapidly converted to the TBDMS ether under acidic conditions (eq 9). Other silyl groups could also be introduced by using silylphos-phines having the corresponding silyl group. 

The styryltin phosphines (p-CH2=CHCeH4)R2SnPR 2 [R=p-tol, Bu", or (CH2)5 R = Bu or Ph] react with [Ni(CO)4] to give phosphine complexes of the [NiCCOJaL] type. 2 The n.m.r. spectra of 116 complexes of this type (L=P, As, or Sb donor) have been analysed with a view to assessing the ligands Reactions of [Ni(CO)4] with some silylphosphines... 

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