CAAC Boranes. Synthesis and characterization of cyclic (alkyl) (amino) carbene borane complexes from BF₃ and BH₃.
In situ formation of two cyclic (alkyl) (amino) carbenes (CAACs) followed by addition of BF₃•Et₂O provided the first two examples of CAAC-BF₃ complexes: 1-(2,6-diisopropylphenyl)-3,5,5-trimethyl-3-phenylpyrrolidin-2-ylidene trifluoroborane, and 2-(2,6-diisopropylphenyl)-3,3-dimethyl-2-azaspiro[4.5]decan-1-ylidene trifluoroborane. These CAAC-BF₃ complexes are robust compounds that are stable to ambient laboratory conditions and silica gel chromatography. They were characterized by spectroscopy and X-ray crystallography. In contrast, a CAAC complex with borane (BH₃) was readily formed in situ according to ¹H and ¹¹B NMR analysis, but did not survive the workup conditions. These results set the stage for further studies of the chemistry of CAAC boranes.
UPMC Univ. Paris 06, Institut parisien de chimie moléculaire (UMR CNRS 7201), C 229, 4 place Jussieu, 75005 Paris, France. jam287@pitt.edu
Julien
J
Monot
Louis
L
Fensterbank
Max
M
Malacria
Emmanuel
E
Lacôte
Steven J
SJ
Geib
Dennis P
DP
Curran