Synthesis of Some P-Trifluoromethyl-Substituted (Silylamino)phosphines, N-Silylphosphoranimines, and Phosphazenes

Treatment of P-chloro-substituted (silylamino)phosphines, (Me(3)Si)(2)NP(R)Cl, with the trifluoromethylating agent, [(Et(2)N)(3)PBr(+)](CF(3)(-)) [generated in situ from CF(3)Br and (Et(2)N)(3)P], readily affords the corresponding P-trifluoromethylphosphines, (Me(3)Si)(2)NP(R)CF(3) (4, R = Ph; 5, R = n-Pr). Subsequent oxidative halogenation of 4 and 5 with X(2) (X = Cl, Br, I) occurs with loss of Me(3)SiX to yield the P-halo-P-trifluoromethyl-N-silylphosphoranimines, Me(3)SiN=P(R)(CF(3))X (6a-c; R = Ph; 7a-c, R = n-Pr). The P-Br compounds 6b and 7b were then converted to the P-trifluoroethoxy, Me(3)SiN=P(R)(CF(3))OCH(2)CF(3) (8, R = Ph; 9, R = n-Pr), and P-phenoxy, Me(3)SiN=P(R)(CF(3))OPh (10, R = Ph; 11, R = n-Pr), derivatives by nucleophilic substitution reactions with LiOCH(2)CF(3) and LiOPh, respectively. Although these P-CF(3) systems are generally much more thermally stable than their P-alkyl analogs, the P-Br compounds 6b and 7b do thermally eliminate Me(3)SiBr to produce new P-trifluoromethyl substituted phosphazenes [CF(3)(R)P=N](n)(). The cyclic trimers (n = 3; 12, R = Ph; 13, R = n-Pr) were separated from the linear polymers (n approximately 150-500; 14, R = Ph; 15, R = n-Pr) by sublimation. These new compounds (4-15) were generally obtained in good yields and were fully characterized by NMR ((1)H, (1)(3)C, (1)(9)F, and (3)(1)P) spectroscopy and elemental analysis.