Novel polymers having pyridone moieties as well as aromatic systems in the main chain were synthesized by the reaction of an organometallic polymer having cobaltacyclopentadiene moieties in the main chain (1) with various isocyanates (2). When dark brown 1 and 5 equiv of n-butyl isocyanate (2a) were heated in tetrahydrofuran at 120 degrees C for 6 h in a sealed tube, a greenish polymer (3a) was obtained in 99% yield by precipitation with methanol. From the spectroscopic measurements, the resulting polymer was found to contain N-n-butyl-2-pyridone and (eta(4)-cyclobutadiene)cobalt moieties (68% and 32%, respectively). By changing the feed ratio of 2a/1, the composition of a-pyridone and cyclobutadienecobalt moieties could be controlled. Using various isocyanates (2a-2d), 2-pyridone-containing polymers with various substituents were obtained. The cross-linking reaction could be also possible by using diisocyanate (2f).