The Chloronium Cation [(C2H3)2Cl+] and Unsaturated C4-Carbocations with C=C and C≡C Bonds in Their Solid Salts and in Solutions: An H1/C13 NMR and Infrared Spectroscopic Study

Solid salts of the divinyl chloronium (C2H3)(2)Cl+ cation (I) and unsaturated C4H6Cl+ and C4H7+ carbocations with the highly stable CHB(11)Hal(11)(-) anion (Hal=F, Cl) were obtained for the first time. At 120 degrees C, the salt of the chloronium cation decomposes, yielding a salt of the C4H5+ cation. This thermally stable (up to 200 degrees C) carbocation is methyl propargyl, CH equivalent to C-C+-H-CH3 (VI), which, according to quantum chemical calculations, should be energetically much less favorable than other isomers of the C4H7+ cations. Cation VI readily attaches HCl to the formal triple C equivalent to C bond to form the CHCl=CH-C+H-CH3 cation (VII). In infrared spectra of cations I, VI, and VII, frequencies of C=C and C equivalent to C stretches are significantly lower than those predicted by calculations (by 400-500 cm(-1)). Infrared and H-1/C-13 magic-angle spinning NMR spectra of solid salts of cations I and VI and high-resolution H-1/C-13 NMR spectra of VII in solution in SO2ClF were interpreted. On the basis of the spectroscopic data, the charge and electron density distribution in the cations are discussed.