The Chloronium Cation [(C 2 H 3 ) 2 Cl + ] and Unsaturated C 4 -Carbocations with C=C and C≡C Bonds in Their Solid Salts and in Solutions: An H 1 /C 13 NMR and Infrared Spectroscopic Study.

Solid salts of the divinyl chloronium (C 2 H 3 ) 2 Cl + cation ( I ) and unsaturated C 4 H 6 Cl + and C 4 H 7 + carbocations with the highly stable CHB 11 Hal 11 - anion (Hal=F, Cl) were obtained for the first time. At 120 °C, the salt of the chloronium cation decomposes, yielding a salt of the C 4 H 5 + cation. This thermally stable (up to 200 °C) carbocation is methyl propargyl, CH≡C-C + -H-CH 3 ( VI ), which, according to quantum chemical calculations, should be energetically much less favorable than other isomers of the C 4 H 7 + cations. Cation VI readily attaches HCl to the formal triple C≡C bond to form the CHCl=CH-C + H-CH 3 cation ( VII ). In infrared spectra of cations I , VI , and VII , frequencies of C=C and C≡C stretches are significantly lower than those predicted by calculations (by 400-500 cm -1 ). Infrared and 1 H/ 13 C magic-angle spinning NMR spectra of solid salts of cations I and VI and high-resolution 1 H/ 13 C NMR spectra of VII in solution in SO 2 ClF were interpreted. On the basis of the spectroscopic data, the charge and electron density distribution in the cations are discussed.