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 (C H ) 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).

Carbene‐Stabilized Disilicon as a Silicon‐Transfer Agent: Synthesis of a Dianionic Silicon Tris(dithiolene) Complex

“…may well serve as a convenient synthetic platform from which various main group‐based dithiolenes could be synthetically approached. For example, both boron dithiolene radicals and magnesium dithiolene complexes have recently been synthesized by utilizing 2 . .…”

Carbene‐Stabilized Dithiolene (L0) Zwitterions

“…[5c, 19] To the best of our knowledge, the literature does not reveal a report of stable carbene-, or silylene-, mediated cleavage of a sulphur-sulphur bond (in a molecular compound). The dramatic colour difference between 3 and 5 may be related to their distinct HOMO-LUMO energy gaps [DE HOMO-LUMO = 2.08 eV (3) and 2.88 eV (5)]. [8] Compound 5 is largely insoluble in benzene and toluene.…”

“…[2f] For example, this laboratory recently reported the synthesis and molecular structure of lithium dithiolene radical (Scheme 1), [4] which provides a unique synthetic platform for accessing the largely unexplored dithiolene chemistry of main group elements. [5] In contrast to dithiolate dianions (L 2À , containing six p-electrons), the 4pe-containing neutral dithiolene (L 0 ) is an electron-deficient system, thus inclined to seek electron-rich species. [2i] Neutral dithiolenes (L 0 ) have been reported to exist as dithiones and dithietes (Figure 1).…”

Bis(triphenylphosphine)iminium Salts of Dioxothiadiazole Radical Anions: Preparation, Crystal Structures, and Magnetic Properties

“…Achievement of such advanced properties requires, however, an expansion of the library of easily accessible and electroactive molecules with relatively stable radical forms. The most commonly studied radicals comprise α-diimines [12], dithiolenes [13][14][15], oxolenes [16,17], nitronyl nitroxides [18,19], tetrathiafulvalene (TTF) derivatives [20], π-conjugated macrocycles [21], TCNE and TCNQ derivatives [22][23][24][25], and verdazyl radicals [26].…”