New Route to Dehydroannulenes by Coupling Linear Polyynes Using Ruthenium Carbonyl

The reaction of FcC⋮CC⋮CC⋮CC⋮CFc, 1, with Ru3(CO)12 has yielded the novel cyclic polyyne [Ru2(CO)6{μ-(Fc)C4(Fc)C⋮CC⋮C}]2, 2, where Fc = (C5H5)Fe(C5H4) by a ruthenium-induced coupling of two molecules of 1 at both ends of the molecule. The molecule contains a planar cyclic tetrayne with two Ru2(CO)6 metallacycles. All four ferrocenyl groups lie on the same side of the ring. The differential pulse voltammogram of 2 shows two oxidation peaks separated by 47 mV.