The reactions between tris(primary amino)boranes and boron trifluoride: alkylaminoboron difluorides and primary amine–boron trifluoride adducts

Abstract

The products of the reaction between tris(primary amino)boranes and boron trifluoride have been shown to depend on the nature of the alkyl group present. When R = Prⁱ or Bu^t the product is the primary aminoboron difluoride dimer, (RNHBF₂)₂, whereas when R = Me, Et, Prⁿ, or Buⁱ the product is the corresponding primary amine–boron trifluoride adduct together with various substituted borazines. Likewise tris(ethylamino)borane undergoes a novel reaction with boron trichloride to a quantitative yield of ethylamine—boron trichloride and B-trichloro-N-triethylborazine, (EtNBCl)₃. Some transammination reactions of diethylamino-boron difluoride are also described.

The proton, boron, and fluorine nuclear magnetic resonance spectra of these compounds are recorded. The occurrence of long-range proton–boron coupling is discussed and it is also shown that the alkyl groups in isopropylaminoboron difluoride dimer are in the trans configuration with respect to the plane of the ring.