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.