An Electronic Structure Study of the Conversion from 1,2-Diphenylacetylene to (E)-1,2-Diphenylethene Using a Bidentate Ru(II)-NC Catalyst

The {(C5H4N)(C6H4)}RuCl(CO)(PPh3)(2) catalyst has been shown to be highly efficient and selective for semi-hydrogenation reactions with a wide range of internal alkynes containing electron-withdrawing and electron-donating groups to E-alkenes. In this work, the reaction mechanism previously proposed by experimentalists to the formation of (E)-1,2-diphenylethene from 1,2-diphenylacetylene (Organometallics, 2020, 39, 862) is evaluated by using the Density Functional Theory. Our calculations show the existence of four new intermediates to avoid steric hindrance issues and to explain the releasing of the (Z)-1,2-diphenylethene and (E)-1,2-diphenylethene products at the end of the first and second cycles, respectively. Besides, by using the energetic span model, the turnover frequency (TOF)-determining transition state (TDTS) and intermediate (TDI) are found in the first cycle, providing an energetic span for the catalytic cycle of 16.8 kcal/mol at 383.15 K. This result assures that the reaction can really proceed by this mechanism.

Automated summary

In this study, the reaction mechanism of the semi-hydrogenation reaction catalyzed by {(C5H4N)(C6H4)}RuCl(CO)(PPh3)(2) catalyst was evaluated using Density Functional Theory. The calculations revealed the existence of four new intermediates to overcome steric hindrance issues and explained the release of the products. Additionally, the turnover frequency (TOF)-determining transition state (TDTS) and intermediate (TDI) were identified in the first cycle using the energetic span model.