Alkylidene and alkylidyne surface complexes: Precursors and intermediates in alkane conversion processes on supported single-site catalysts

Well-defined surface alkylidenes and alkylidynes can be compared to their molecular counterparts in structural features and formation pathways, but their reactivity towards alkanes is strikingly different. They catalyse the metathesis of alkanes and cross-metathesis of alkanes, whereas no single-component molecular system is known to do so. Herein, we study such reactivity in terms of structure–activity relationships, to further propose a comparison to the reactivity of well-defined group 4–6 supported hydrides, focused on the alkane metathesis and alkane hydrogenolysis processes. There, the formation of intermediates containing alkylidenes and alkylidynes nicely pinpoints their pre-eminence in the catalytic conversion of alkanes, always in agreement with the elementary steps of molecular organometallic chemistry. Finally, a number of relevant reactions where the formation of alkylidene/alkylidyne intermediates has been presumed are also presented.