Cationic Bismuth Amides Add across Activated C═X Bonds (X = C, N, and S): Pronounced Solvent Effects on Reactivity and Selectivity

Abstract

The reactivity of a literature-known, ring-strained cationic bismuth amide toward the unsaturated substrates RNCNR, CS2, and acrylonitrile is reported (R = iPr, Cy, and pTol). Subtle changes in the polarity of the reaction medium (THF vs pyridine) can be exploited to selectively address two different reaction pathways. Either the dinuclear nature of the starting material is preserved, only one substrate molecule per two bismuth atoms is incorporated into the product, and an aryl migration is possible or well-defined mononuclear compounds with a Bi/substrate ration of 1:1 are observed. These findings correlate with an unexpected increase in reactivity of the cationic bismuth species, when the polarity of the solvent is increased from THF to pyridine, and are likely to be connected to the nuclearity of the cationic bismuth amide starting material.

Insertion of CO2and CS2into Bi–N bonds enables catalyzed CH-activation and light-induced bismuthinidene transfer

“…Mononuclear model systems were chosen based on the investigations of their aggregation behavior ( vide supra ), to keep the computational approach feasible at a sufficiently high level of theory, and because a higher reactivity for mononuclear species has been proposed in related systems. 34 We suggest a heterolytic cleavage of the Bi–E bond as the initiating step of the reaction to give the charge-separated intermediate Int-1-E . This intermediate is energetically more favorable for E = O than for E = S due to stabilization of the negative charge by the electronegative oxygen atoms in the (R 2 NCO 2 ) − moiety.…”