The complex (η(5)-C(5)H(5))Ir(η(4)-C(6)H(6)) reacts with Grubbs' catalyst to give a novel polyacetylene consisting of cyclopentadienyliridium bound s-cis butadiene moieties separated by C=C linkages. A crystal structure of the pentamethylcyclopentadienyl analog establishes a strong structural analogy with norbornadiene, a classical ROMP monomer.