The halogen effect on the ring-opening of germacyclopropylidenoids to germaallenes

Density functional theory calculations were employed to explore the ring-opening reaction mechanisms of mono germanium analogues of cyclopropylidenoids via Doering-Moore-Skattebol method. The theoretical findings revealed that the stepwise fashion with the intermediacy of a free germacyclopropylidene is operative for the structure with germanium atom on the carbenic position (1). Moreover, the cyclopropylidene analogue (4) of the title structures proceeds via concerted manner for the corresponding ring-opening reaction. The calculated overall energy barrier to trigger the stepwise ring-opening reaction for 1 is strongly higher than the concerted fashion for 4. Additionally, the effect of halogens (X = F, Cl, Br) on the reaction mechanism were also investigated. The energy barriers for chlorine substituted precursors are found to be lower than the fluorine and bromine substituted forms.