Mechanistic, Computational Study of Alkene-Diazene Heterofunctional Cross-Metathesis Catalyzed by Ruthenium Complexes

Density functional theory calculations were used to study the cross-metathesis reaction between diazenes and alkenes catalyzed by 17 different ruthenium complexes. Density functional theory (DFT) calculations show that such a transformation is possible for properly designed catalysts. The highest estimated reaction rates were predicted for first-generation Hoveyda–Grubbs and indenylidene catalysts. In both cases, the energy barriers of the limiting step of the entire catalytic cycle were predicted to be significantly lower compared to all other studied catalysts and suggest that such a process is possible under mild temperature conditions. Moreover, to better understand the still unclear mechanism of azo metathesis, competing reactions that may take place in the reaction mixture were also analyzed. It was found that the association of an imine molecule instead of an olefin by the active ruthenium complex in the propagation part of the catalytic cycle may compete with diazene-alkene cross-azo metathesis.