Competition between the stabilizing effects of saturated alkyl substituents and pi bonds on complexes of silver ion (Ag+) with alkenes

The coordination of Ag+ ions to alkenes is of both theoretical and practical interest. While much attention has been paid to how the nature of the C=C pi bond affects the coordinative process, little attention has been directed toward the effect of saturated side chains on complex stabilization despite experimental evidence suggesting its importance. Calculations employing the M06-2X DFT functional have revealed that saturated chains can exhibit as powerful a stabilizing effect on Ag+/alkene complex formation as increased alkyl substitution about the C=C bond. Natural bond orbital (NBO) analysis confirms the mechanism of stabilization to be that of agostic interactions of properly-oriented CH sigma-bonds in the saturated chain with the Ag+ ion. Analysis by the extended transition state energy decomposition approach with the natural orbital for chemical valence method (ETS-NOCV) and the reduced density gradient (RDG) model were used to better characterize the nature of the interaction as a near equivalent combination of electrostatic and orbital interactions.

Automated summary

This study found that saturated chains can have a stabilizing effect on the formation of Ag+/alkene complexes as powerful as increased alkyl substitution around the C=C bond. The mechanism of stabilization is mainly achieved through agostic interactions between properly-oriented CH sigma-bonds in the saturated chain and the Ag+ ion. Analysis using ETS-NOCV and RDG models showed that the interaction nature is a near equivalent combination of electrostatic and orbital interactions.