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

Abstract

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.