Stable Boron Dithiolene Radicals

Whereas low‐temperature (−78 °C) reaction of the lithium dithiolene radical 1 . with boron bromide gives the dibromoboron dithiolene radical 2 . , the parallel reaction of 1 . with (C 6 H 11 ) 2 BCl (0 °C) affords the dicyclohexylboron dithiolene radical 3 . . Radicals 2 . and 3 . were characterized by single‐crystal X‐ray diffraction, UV/Vis, and EPR spectroscopy. The nature of these radicals was also probed computationally. Under mild conditions, 3 . undergoes unexpected thiourea‐mediated B−C bond activation to give zwitterion 4 , which may be regarded as an anionic dithiolene‐modified carbene complex of the sulfenyl cation RS + (R=cyclohexyl).