Stable Boron Dithiolene Radicals.

Abstract: 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 (C₆H₁₁)₂BCl (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). [ABSTRACT FROM AUTHOR]