The halogen effecton the ring-opening ofgermacyclopropylidenoids to germaallenes

Özet

Density functional theory calculations wereemployed to explore the ring–opening reaction mechanisms of mono germanium analogues of cyclopropylidenoids viaDoering–Moore–Skattebøl method. The theoreticalfindings revealedthat the stepwise fashion with the intermediacy of a free germacyclopropylidene is operative for the structure with germaniumatom on the carbenic position (1). Moreover, the cyclopropylidene analogue (4) of the title structures proceedsviaconcerted manner for the corresponding ring-opening reaction. The calculated overall energy barrier to trigger the stepwise ring-opening reaction for 1is strongly higher than the concerted fashion for 4. Additionally, the effectof 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.