Computational Design of Neutral Heteronuclear Alkaline‐Earth Metal Complexes Featuring a 2c─3e Bond and Their Application in CO 2 Activation

In contrast to electron‐paired bonds, odd‐electron bonding systems have garnered significant interest due to their distinctive bonding and radical properties. A series of neutral heteronuclear (AEM–AEM′)AMD (AEM = Be, Mg, and Ca) complexes was theoretically designed by binding two distinct alkaline‐earth‐metal (AEM) atoms with amidinate radical ligands (AMD) via side‐on coordination. Upon one‐electron transfer from AEM–AEM′ to AMD, the electron occupies an AMD nonbonding orbital, avoiding destabilization from rising ligand orbital energy, while a two‐center three‐electron (2c─3e) bond forms between the two AEMs. Subsequent CO 2 activation studies show that (Mg─Ca)AMD exhibits the highest activity, a net electron transfer of 1.46 |e| derived from a two‐electron redox process, accompanied by activation indicators: elongation of the C─O bond length (from 1.160 to 1.248 Å), reduction of the Wiberg bond index (from 1.816 to 1.454) and decrease of the flexible force constant (from 16.667 to 6.410 mDyn/Å). Investigation of CO 2 conversion reveals CO formation with monotonically decreasing free energies. Although methane is the thermodynamically more favorable product, its formation encounters three energy‐consuming steps, making the free‐energy profile nonmonotonic. This work extends heteronuclear odd‐electron bonding into the s‐block and provides a route for CO 2 activation using alkaline‐earth systems beyond transition‐metal or main‐group catalysts.