Carbodicarbene Bismaalkene Cations: Unravelling the Complexities of Carbene versus Carbone in Heavy Pnictogen Chemistry

• Published in: Angewandte Chemie International Edition 2021-03, Vol.60 (12), p.6682-6690
• Main Authors: Walley, Jacob E., Warring, Levi S., Wang, Guocang, Dickie, Diane A., Pan, Sudip, Frenking, Gernot, Gilliard, Robert J.
• Format: Article
• Language: English
• Subjects: bismaalkenes; Bismuth; carbenes; carbodicarbenes; Cations; Ligands; low-coordinate compounds
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202014398

We report a combined experimental and theoretical study on the first examples of carbodicarbene (CDC)‐stabilized bismuth complexes, which feature low‐coordinate cationic bismuth centers with C=Bi multiple‐bond character. Monocations [(CDC)Bi(Ph)Cl][SbF6] (8) and [(CDC)BiBr2(THF)2][SbF6] (11), dications [(CDC)Bi(Ph)][SbF6]2 (9) and [(CDC)BiBr(THF)3][NTf2]2 (12), and trication [(CDC)2Bi][NTf2]3 (13) have been synthesized via sequential halide ions from (CDC)Bi(Ph)Cl2 (7) and (CDC)BiBr3 (10). Notably, the dications and trication exhibit C⇉ Bi double dative bonds and thus represent unprecedented bismaalkene cations. The synthesis of these species highlights a unique non‐reductive route to C−Bi π‐bonding character. The CDC‐[Bi] complexes (7–13) were compared with related NHC‐[Bi] complexes (1, 3–6) and show substantially different structural properties. Indeed, the CDC ligand has a remarkable influence on the overall stability of the resulting low‐coordinate Bi complexes, suggesting that CDC is a superior ligand to NHC in heavy pnictogen chemistry. Unprecedented low‐coordinate carbodicarbene bismaalkene cations have been prepared which feature C⇉ Bi double dative bonds. The synthesis of these compounds represents a unique non‐reductive route to C=Bi double‐bond character.