Synthesis of some P-trifluoromethyl-substituted (silylamino) phosphines, N-silylphosphoranimines, and phosphazenes

Treatment of P-chloro-substituted (silylamino)phosphines, (Me3Si)(2)NP(R)Cl, with the trifluoromethylating agent, [(Et2N)(3)PBr+](CF3-) [generated in situ from CF3Br and (Et2N)(3)P], readily affords the corresponding P-trifluoromethylphosphines, (Me3Si)(2)NP(R)CF3 (4, R = Ph; 5, R = n-Pr). Subsequent oxidative halogenation of 4 and 5 with X-2 (X = Cl, Pr, I) occurs with loss of Me3SiX to yield the P-halo-P-trifluoromethyl-N-silylphosphoranimines, Me3SiN=P(R)(CF3)X (6a-c; R = Ph; 7a-c, R = n-Pr). The P-Br compounds 6b and 7b were then converted to the P-trifluoroethoxy, Me3SiN=P(R)(CF3)OCH2CF3 (8, R = Ph; 9, R = n-Pr), and P-phenoxy, Me3SiN=P(R)(CF3)OPh (10, R = Ph; 11, R = n-Pr), derivatives by nucleophilic substitution reactions with LiOCH2CF3 and LiOPh, respectively. Although these P-CF3 systems are generally much more thermally stable than their P-alkyl analogs, the P-Br compounds 6b and 7b do thermally eliminate Me3SiBr to produce new P-trifluoromethyl substituted phosphazenes [CF3(R)P=N](n). The cyclic trimers (n = 3; 12, R = Ph; 13, R = n-Pr) were separated from the linear polymers (n similar to 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 (H-1, C-13, F-19, and P-31) spectroscopy and elemental analysis.