A Stable Anionic Dithiolene Radical

Sulfurization
of anionic N-heterocyclic dicarbene, [:C­{[N­(2,6-Pri2C6H3)]2CHCLi}]n (2), with
elemental sulfur (in a 1:2 ratio) in Et2O 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 GeCl2·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.