Alkynophilicity of Group 13 MX3 Salts: A Theoretical Study

The concept of alkynophilicity is revisited with group 13 MX3 metal salts (M = In, Ga, Al, B; X = Cl, OTf) using M06-2X/6-31+G(d,p) calculations. This study aims at answering why some of these salts show reactivity toward enynes that is similar to that observed with late-transition-metal complexes, notably Au(I) species, and why some of them are inactive. For this purpose, the mechanism of the skeletal reorganization of 1,6-enynes into 1-vinylcyclopentenes has been computed, including monomeric (standard) and dimeric (superelectrophilic) activation. Those results are confronted with deactivation pathways based on the dissociation of the M-X bond. The role of the X ligand in the stabilization of the intermediate nonclassical carbocation is revealed, and the whole features required to make a good pi-Lewis acid are discussed.

Automated summary

This study revisits the concept of alkynophilicity using group 13 MX3 metal salts, focusing on the reactivity of these salts towards enynes and the role of the X ligand in stabilizing intermediate nonclassical carbocations. Computational calculations reveal the mechanisms of skeletal reorganization and the features required to make a good pi-Lewis acid.