SYNTHESIS AND REACTIONS OF P-SUPERMESITYL-C-HALOPHOSPHAALKENES

C-Halophosphaalkenes (1, 2) were prepared in high yield by a one-pot synthesis from HCX3 or CI4 and Mes*PCl2 (Mes* = supermesityl = 2,4,6-tri-tert-butylphenyl). The C-iodophosphaalkenes Mes*P = CI2 (1 c) and Mes*P = CHI (2 c) undergo halogen-metal exchange with n-BuLi at low temperatures. The resulting carbenoids Mes*P = CILi (11 c) and Mes*P = CHLi (6) reacted with ClMMe3 (M = Si, Ge, Sn) to give Mes*P = CIMMe3 [(Z)-13: M = Ge; (Z)-14: M = Sn] or Mes*P = CHMMe3 (8-10), respectively. Further reaction of (Z)-13 and (Z)-14 with nBuLi and ClMMe3 gave Mes*P = C(MMe3)2 (18: M = Ge; 19: M = Sn). The carbenoid (Z)-11 c decomposed at -85-degrees-C; instead of the expected ''phosphaisonitrile'' Mes*P = C: (21), only Mes*C = P (15) was obtained which lends experimental support to the theoretically predicted instability of 21.