Isolation of bicyclopropenylidenes: Derivatives of the smallest member of the fulvalene family

(Figure Presented) Small and stable: A triafulvalene derivative is indefinitely stable at room temperature both in solution and in the solid state under inert atmosphere. The triafulvalene is synthesized by the magnesium-catalyzed coupling of two bis(chlorocyclopropenyl) derivatives. The two unsaturated three-membered rings are linked together by a carbon-carbon double bond (1.303 Å, see structure), which is so reactive that spontaneous addition of water occurs at room temperature.