N-Heterocyclic Carbene Analogues of Wittig Hydrocarbon

N-Heterocyclic carbene (NHC) analogues of Wittig hydrocarbon, [(NHC)(Stil)(NHC)] (3a-c) (NHC = SIPr (1a) = C[N(Dipp)CH²]₂, Dipp = 2,6-iPr₂C₆H₃; IPr (1b) = C[N(Dipp)CH]₂; Me-IPr (1c) = C[N(Dipp)CMe]₂ and Stil = C₆H₄CHCHC₆H₄) have been reported as crystalline solids. 3a-c are prepared by two-electron reductions of the corresponding bis-1,3-imidazoli(ni)um bromides [(NHC)(Stil)NHC)](Br)₂ (2a-c) with KC₈ in >94 % yields. 2a-c are accessible by the nickel catalyzed direct C−C coupling of NHCs (1a-c) with (E)-4,4'-dibromostilbene. One-electron oxidation of 3a,b yields the corresponding radical cations [(NHC)(Stil)NHC)]B(C₆F₅)₄ 4a,b. All compounds have been characterized by UV-Vis/NMR/EPR spectroscopy as well as 2a, 3a, and 3b by single crystal X-ray diffraction. The electronic structures of representative systems have been analyzed by quantum chemical calculations.