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.