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.