Lewis Acid Stabilized Diatomic Molecules of Group 14: A Computational Study on [(CO) 4 Fe] 2 E 2 (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) 4 Fe] 2 E 2 , 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.