REACTIONS OF A CARBOSILYLATED METHYLENEPHOSPHONIUM ION WITH PI-CONJUGATED HYDROCARBONS

In the C-silylated methylenephosphonium salt [(Bu2P)-Bu-t=CHSiMe3](+) AlCl4- (6) cation and anion are separated in the solid state and in so lution. Adding an excess of AlCl3, however, does not allow the synthes is of the methylenephosphonium salt 6' with Al2Cl7- as counteranion bu t leads to the adduct (Bu2PCl)-Bu-t-CHSiMe3 . Al2Cl6 (7) which was cha racterized by an X-ray analysis. Electron-rich pi-conjugated hydrocarb ons Like fulvene 9 or anthracene 10 react with 6 (or 7) under formatio n of [2+4]-cycloadducts 11a,b and 12, respectively, while electron-poo r systems (benzene, naphthalene, C-60) are unreactive. (C) 1997 Elsevi er Science S.A.