N-Heterocyclic Carbene Derived 3-Azabutadiene as a π-Base in Classic and Frustrated Lewis Pair Chemistry |
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Authors: | Youngsuk Kim Dr Liu Leo Liu Prof Dr Douglas W Stephan |
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Institution: | Department of Chemistry, University of Toronto, 80 St. George St. Toronto, Ontario, M5S3H6 Canada |
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Abstract: | 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 AlCl3, GaCl3, and Me2SAuCl, to form diverse classic Lewis adducts 3 – 5 . Combination of 1 with B(C6F5)3 or Ph3C]B(C6F5)4] 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 BPh3 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. |
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Keywords: | carbenes frustrated Lewis pairs Lewis acids Lewis bases single-electron transfer |
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