Dialkyl Chloronium Ions

The carborane acid H(CHB11Cl11) reacts with chloroalkanes RCl to give isolable dialkylchloronium ion salts, [R2Cl][CHB11Cl11], that are stable at room temperature. X-ray crystal structures have been obtained for R = CH3 and CH2CH3, revealing bent cation structures with C-Cl-C angles of 101.5 and 105.8 degrees, respectively. The dimethylchloronium ion salt loses CH,Cl upon heating and forms sublimable CH3(CHB11Cl11), providing a clean synthetic route to an extremely potent electrophilic methylating agent. IR spectra of all species have been interpreted, including the C-Cl stretch in CH3-ClCHB11Cl10.