Reactivity of Heavier Vinyl Anions [(CH₃)₂EE′(CH₃)]⁻ (E, E′ = C, Si, Ge) toward Carbon Monoxide: A Computational Study

The structures of heavier vinyl anions [(CH3)2EE′(CH3)]− (E, E′ = C, Si, Ge) and their abilities to activate carbon monoxide were investigated by DFT. Particularly, heteronuclear species exhibit a strong influence of the position of the heavier of the two group 14 elements (E or E′) with strongly differing singlet–triplet gaps as a measure of tetrylene character. The reactions of CSi and CGe (E′ = Si, Ge) with CO proceed in a concerted manner via [1 + 2] or [2 + 2] cycloadditions to a variety of potential products, whereas those of positional isomers as well as digerma and sila-germa analogues occur in a stepwise fashion. The three-membered rings derived from tetrylene-like vinyl anions (E′ = Si, Ge and E = C) are dominated by keto resonance structures, while an enol structure is observed for the product obtained from SiC. Allene-like isomers could only be optimized in case of E = Si, Ge.