N-Heterocyclic Carbene Derived 3-Azabutadiene as a π-Base in Classic and Frustrated Lewis Pair Chemistry.

N-Heterocyclic carbene (NHC) derived 3-azabutadienes 1 and 2 have been prepared by a single-step reaction of the corresponding NHC with cyclohexyl isocyanide. Compound 1 features π-basic, delocalized nucleophilic sites over the 3-azabutadiene moiety, therefore allowing for coordinating with small Lewis acids, such as AlCl , GaCl , and Me SAuCl, to form diverse classic Lewis adducts 3-5. Combination of 1 with B(C F ) or [Ph C][B(C F ) ] resulted in single-electron transfer and the obtained radical cation was detected by EPR. In addition, a frustrated Lewis pair comprised of the π-basic 1 and BPh effects the splitting of the O-H bond of phenol and the N-H bond of imidazole to give 7 and 8, respectively. An intrinsic bond orbital (IBO) analysis of the pathway leading to 8 showcases the transformation of the delocalized π-electrons of 1 to a newly formed C-H localized σ-bond.