Preparation of Novel Fluoro Derivatives of Amine Cyanoboranes and Amine Carboxyborane Esters

Sonication of the amine mono- and dibromocarboxyborane esters or the amine mono- and dibromocyanoboranes with excess AgF results in rapid incorporation of fluorine by bromine/fluorine exchange to
provide the difluoro derivatives of amine cyanoboranes
and amine carboxyborane esters, 1−10, in yields of 59−70%. Bromination of the amine monofluorocyanoboranes
and amine monofluorocarboxyborane ester derivatives
successfully afforded the expected amine bromofluoro
derivatives, 11 and 12, in yields of 57−62%. This was
confirmed by NMR shifts for all compounds. The pKa
value for the fluorinated amine carboxyborane 13 was
determined and found to be 5.15 compared to 8.38 for
Me3N:BH2COOH, in line with expectations. The molecular structure for compound 1 was determined by X-ray
crystallography.