A Viable Anionic N-Heterocyclic Dicarbene

The first anionic N-heterocyclic dicarbene, polymeric [:C{[N(2,6-Pri2C6H3)]2CHCLi(THF)}]n 1, containing both normal (C2) and abnormal carbene (C4) centers in the same five-membered imidazole ring (III), has been prepared by lithiation of the imidazole monocarbene, :C{N(2,6-Pri2C6H3)CH}2. The dicarbene nature of 1 was unambiguously demonstrated by the formation of the group 13 Lewis acid adducts (THF)2Li:C{[N(2,6-Pri2C6H3)]2CHC(LA)}, where LA = AlMe3 [2·(THF)2] and BEt3 [3·(THF)2].