Imidazolium Dicyanomethylides as N‐Ylide Precursors of Anionic N‐Heterocyclic Carbenes.

In the past, the use of nitrogen ylides focused primarily on cycloadditions, where the 1,3‐dipole was used as a building block for the formation of heterocycles such as pyrroles or pyrrolinones. In this work, we present a new perspective on imidazolium dicyanomethylides with their synthesis and utilization as anionic N‐heterocyclic carbenes (NHCs). The values of relative carbene formation energies (CREF) for a wide range of substituted imidazolium ylides unknown in the literature showed promising properties. In situ trapping reactions of these anionic NHCs with selenium led to anionic, water‐soluble compounds that exhibited remarkable coordination behavior according to X‐ray structure analyses. In addition, the 77Se shifts of the investigated compounds were measured to draw conclusions about their π‐acceptance. [ABSTRACT FROM AUTHOR]