Synthesis and reactivity of (Silylamino)-phosphines with P-H bonds

Abstract

The reactions of a series of {bis(trimethylsilyl)amino}(chloro)phosphines (Me(,3)Si)(,2)NP(R)Cl with i-PrMgCl were studied in detail and found to generally yield mixtures of the iso-propyl substitution products (Me(,3)Si)(,2)NP(R) (i-Pr) and reduction products (Me(,3)Si)(,2)NP(R)H {R = i-Pr, t-Bu, CH(,2)SiMe(,3), N(SiMe(,3))(,2), and Ph}. The P-H substituted phosphines appear to be formed by an unexpected side reaction in which i-PrMgCl acts as a reducing agent with elimination of propylene. This reaction is catalyzed by magnesium salts and the product distribution appears to be dependent on the steric bulk of the phosphorus substituents. Increase in the steric bulk of the phosphorus substituent (R) increases the relative amount of reduced product. Also, in a more direct synthesis, the same P-H substituted phosphines are prepared by the reduction of the chlorophosphines with LiAlH(,4). Further investigation of some simple derivative chemistry of these new P-H phosphines is also described. Included are their reactions with Me(,3)SiN(,3), MeI, and t-BuO(,2)SiMe(,3). The products of the reactions with Me(,3)SiN(,3) and t-BuO(,2)SiMe(,3) were sometimes found to yield both P-H and isomeric N-H compounds. Again, the product mixtures appear to be dependent on the steric bulk of the phosphorus substituents. However, the reactions with MeI, which also afford both P-H and N-H compounds, are dependent on the stoichiometry of the reaction.