Imine chloroboration: reaction of boron trichloride with a bulky diazadiene gives not a diazaborolium salt, but a 2,4,5-trichloro-1,3,2-diazaborolidine

Reaction of N,N'-bis(2,6-diisopropylphenyl)-1,4-diazadiene with BCl3 in hexane gave the crystalline product of double chloroboration, N,N'-bis(2,6-diisopropylphenyl)2,4,5-tri- chloro-1,3,2-diazaborolidine, which was characterised by single crystal X-ray diffraction, microanalysis and multinuclear NMR spectroscopy.