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)44a,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. [ABSTRACT FROM AUTHOR]