A Stable Anionic Dithiolene Radical.

Sulfurization of anionic N-heterocyclic dicarbene, [:C{[N(2,6-PrCH)]CHCLi}] (2), with elemental sulfur (in a 1:2 ratio) in EtO at low temperature gives 3 by inserting two sulfur atoms into the Li-C (i.e., C2 and C4) bonds in polymeric 2. Further reaction of 3 with 2 equiv of elemental sulfur in THF affords 4 via unexpected C-H bond activation, which represents the first anionic dithiolene radical to be structurally characterized in the solid state. Alternatively, 4 may also be synthesized directly by reaction of 1 with sulfur (in a 1:4 ratio) in THF. Reaction of 4 with GeCl·dioxane gives an anionic germanium(IV)-bis(dithiolene) complex (5). The nature of the bonding in 4 and 5 was probed by experimental and theoretical methods.