Isolation of base stabilized fluoroborylene and its radical cation

The synthesis and characterization of metal-free fluoroborylene [(Me-cAAC) 2 BF] ( 1 ) is reported.

Herein, we report the synthesis and characterization of the metal free low valent fluoroborylene [(Me-cAAC) 2 BF] ( 1 ) stabilized by cyclic (alkyl)(amino) carbene (cAAC). The fluoroborylene 1 is obtained by the reductive defluorination of Me-cAAC:BF 3 with 2.0 equivalents of KC 8 in the presence of 1.0 equivalent of Me-cAAC. Due to its highly electron rich nature, 1 underwent one-electron oxidation with 1.0 equivalent of lithium tetrakis(pentafluorophenyl)borate [LiB(C 6 F 5 ) 4 ] to form the radical cation [(Me-cAAC) 2 BF]˙ + [B(C 6 F 5 ) 4 ] − ( 2 ). DFT studies suggested that the lone pair of electrons is localized on the boron atom in 1 , which explains its unprecedented reactivity. Both compounds 1 and 2 were characterized by X-ray crystallography. The radical cation 2 was studied by EPR spectroscopy.