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 p K a value for the fluorinated amine carboxyborane 13 was determined and found to be 5.15 compared to 8.38 for Me 3 N:BH 2 COOH, in line with expectations. The molecular structure for compound 1 was determined by X-ray crystallography.