Reaction coordinate analyses of transition metal catalyzed Csingle bondH and Csingle bondS activation steps Original Research Article

The application of first-principle quantum chemical calculations toward analyzing and understanding heterogeneously catalyzed Csingle bondX bond activation is reviewed. More specifically, two industrially relevant systems, methane activation and thiophene desulfurization are discussed. Density functional theoretical (DFT) calculations are used to examine Csingle bondH activation of acetate a precursor to acetate decar☐ylation and Csingle bondS activation of thiophene. Both systems require a sufficient cluster size model for the catalyst in order to predict energetic information, and hence model periodic trends. Csingle bondH activation of acetate closely mimics the activation of methane. The reaction path is characterized by a late transition state with respect to the Csingle bondH bond stretch. There is considerable Msingle bondH and Msingle bondC bond formation. The predicted barrier is +115 kJ/mol. Thiophene hydrodesulfurization which occurs via η1 adsorption of thiophene, is initially activated by hydrogenating thiophene to 2,5 dihydrothiophene (DHT). DHT activation proceeds via a metal atom insertion into the Csingle bondS bond. The formation of an additional Msingle bondS bond (two-fold sulfur) stabilizes the metallocycle intermediate and lowers the barrier of DHT Csingle bondS bond breaking from +250 to +150 kJ/mol.