In ene-yne activation, the least common of the five modes, a single metal species coordinates with the enol alkene and the tethered alkyne, simultaneously activating both moieties for reaction. Nickel, cobalt, and rhenium complexes have all been employed in this manner. A representative example was reported by Malacria et al. in 1994, in which an alkynyl substituted β-ketoester was treated with cyclopentadienyl cobalt complex and irradiation to give disubstituted methylene cyclopentane.