Lewis Acid Stabilized Diatomic Molecules of Group 14: A Computational Study on [(CO)₄Fe]₂E₂ (E = C, Si, Ge, Sn, Pb)

A Lewis base and acid combination has been effectively employed to stabilize and isolate the low-valent group 14 compounds. We report DFT studies on stabilizing low-valent group 14 diatomics as adducts of Lewis acids employing transition metal carbonyl fragment iron tetracarbonyl [Fe(CO)₄] as Lewis acid. Computational studies on [(CO)₄Fe]₂E₂, E = C, Si, Ge, Sn, and Pb, predict five plausible isomers on its potential energy surface: linear (E2_L), bent (E2_B), three-membered (E2_T), dibridged (E2_D), and four-membered (E2_F). For the carbon analogue, the lowest energy configuration is linear and has a typical cumulenic structure, while silicon and germanium analogues favor three-membered cyclic isomers. Four-membered cyclic isomers are the most stable for tin and lead analogues.