Influence of Coordination to Silver(I) Centers on the Activity of Heterocyclic Iodonium Salts Serving as Halogen-Bond-Donating Catalysts.

Kinetic data based on H NMR monitoring and computational studies indicate that in solution, pyrazole-containing iodonium triflates and silver(I) triflate bind to each other, and such an interplay results in the decrease of the total catalytic activity of the mixture of these Lewis acids compared to the separate catalysis of the Schiff condensation, the imine-isocyanide coupling, or the nucleophilic attack on a triple carbon-carbon bond. Moreover, the kinetic data indicate that such a cooperation with the silver(I) triflate results in prevention of decomposition of the iodonium salts during the reaction progress. XRD study confirms that the pyrazole-containing iodonium triflate coordinates to the silver(I) center via the pyrazole N atom to produce a rare example of a pentacoordinated trigonal bipyramidal dinuclear silver(I) complex featuring cationic ligands.

Diaryliodoniums as Hybrid Hydrogen- and Halogen-Bond-Donating Organocatalysts for the Groebke-Blackburn-Bienaymé Reaction.

Dibenziodolium and diphenyliodonium triflates display high catalytic activity for the multicomponent reaction that leads to a series of imidazopyridines. Density functional theory (DFT) calculations indicate that both the salts can play the role of hybrid hydrogen- and halogen-bond-donating organocatalysts, which electrophilically activate the carbonyl and imine groups during the reaction process. The -H atoms in the vicinal position to the I atom play a dual role: forming additional noncovalent bonds with the ligated substrate and increasing the maximum electrostatic potential on the σ-hole at the iodine atom owing to the effects of polarization.

Predicting the catalytic activity of azolium-based halogen bond donors: an experimentally-verified theoretical study.

This report demonstrates the successful application of electrostatic surface potential distribution analysis for evaluating the relative catalytic activity of a series of azolium-based halogen bond donors. A strong correlation ( > 0.97) was observed between the positive electrostatic potential of the σ-hole on the halogen atom and the Gibbs free energy of activation of the model reactions (, halogen abstraction and carbonyl activation).