Cover Feature: The Noble Addendum of a Phosphenium Ligand to a Base Metal: Coordination, Activation, and Hydrogenation of Alkenes and Alkynes on a Chromium Complex (ChemPlusChem 6/2024)

The cover feature image illustrates the chemical diversity of the force behind the chemistry of a bis-phosphenium complex of chromium arising from photochemical stimulation ("the bright side") and thermally induced follow-up processes ("the dark side"). This reactivity allows to accomplish the catalytic hydrogenation of alkenes via two complementary molecular pathways: a photochemical route, which proceeds under the action of a lightsaber (Sorry: under continuous irradiation) and involves a σ-H2-complex as key intermediate, or in a dark reaction in which a π-alkene complex created in an initial photoreaction plays a central role. Another facet of the dark side is the ligand exchange reaction of the π-complex with alkynes to produce metallacycles, which represent the products of a [2+2]-cycloaddition and can be slashed in a photo-hydrogenation process under recovery of the original bis-phosphenium complex. More information can be found in the Research Article by N. Birchall, M. Nieger and D. Gudat.