Carbodicarbenes: Unexpected π‑Accepting Ability during Reactivity with Small Molecules
datasetposted on 16.08.2017, 00:00 by Wen-Ching Chen, Wei-Chih Shih, Titel Jurca, Lili Zhao, Diego M. Andrada, Chun-Jung Peng, Chun-Chi Chang, Shu-kai Liu, Yi-Ping Wang, Yuh-Sheng Wen, Glenn P. A. Yap, Chao-Ping Hsu, Gernot Frenking, Tiow-Gan Ong
An investigation of carbodicarbenes, the less explored member of the carbenic complex/ligand family has yielded unexpected electronic features and concomitant reactivity. Observed 1,2-addition of E–H bonds (E = B, C, Si) across the carbone central carbon and that of the flanking N-heterocyclic carbene (NHC) fragment, combined with single-crystal X-ray studies of a model Pd complex strongly suggests a significant level of π-accepting ability at the central carbon of the NHC moiety. This feature is atypical of classic NHCs, which are strong σ-donors, with only nominal π-accepting ability. The unanticipated π-acidity is critical for engendering carbodicarbenes with reactivity more commonly observed with frustrated Lewis pairs (FLPs) rather than the more closely related NHCs and cyclic (alkyl)(amino)carbenes (CAACs).