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.
Monot
Julien
J
UPMC Univ. Paris 06, Institut parisien de chimie moléculaire (UMR CNRS 7201), C 229, 4 place Jussieu, 75005 Paris, France. jam287@pitt.edu
Fensterbank
Louis
L
Malacria
Max
M
Lacôte
Emmanuel
E
Geib
Steven J
SJ
Curran
Dennis P
DP