An iridium complex is found to catalyze the selective dehydrogenative coupling of ethylene to 1,3-butadiene. The key intermediate, and a major resting state, is, an iridacyclopentane that undergoes a surprisingly facile beta-H elimination, enabled by a. partial dechelation (kappa(3)-kappa(2)) of the supporting 3,5-dimethylphenyh-2,6-bis(oxazolinyl) ligand.