Boron trichloride adducts of N-substituted benzimidoyl chlorides: nitrilium tetrachloroborates

Boron trichloride and the N-substituted benzimidoyl chlorides PhCCl:NR (R = Me, Et, or Ph) form 1:1 adducts which are formulated as nitrilium tetrachloroborates PhCNR+BCl4– on the basis of their infrared spectra, which have ν(CN) at 2380, 2365, and 2318 cm.–1, respectively. Alkaline hydrolysis of these hydroscopic solid tetrachloroborates gives chloride, borate, and the amide PhCONHR. The alkyl compounds decompose at 150° to give RCl and PhCN,BCl3. N-Benzoylbenzimidoyl chloride forms an adduct PhCCl:N·COPh,BCl3 which is apparently covalent, with co-ordination through nitrogen or oxygen. The chlorides HCl, PhCl, MeCOCl, PhCOCl, and p-Cl·C6H4·COCl do not react with PhCN,BCl3 under mild conditions.