Unravelling the Metastable Nature of the Single Site Tungsten Hydride Metathesis Catalyst Supported on γ-Alumina from First Principles

We explore the structure and formation mechanism of the surface tungsten hydride complex supported on alumina, which is a catalyst for alkane and alkene metathesis and cross-metathesis. We show that the kinetics for the formation reaction of the hydride from the grafted alkylidyne–alkyl W complex strongly favors the creation of a metastable Wⱽᴵ trihydride, which is less coordinated by the alumina surface than the most stable isomer. The reaction network for the hydride formation involves hydrogenation of the W≡C or W═C bond, hydrogenolysis of W–C bonds, and a second grafting step. The creation of metastable surface complexes is proposed to be a key path for the design of active and selective catalysts.