An organometallic iridium compound having low melting point, excellent vaporization characteristic and low film formation temperature on a substrate, a process for producing the compound, and a process for preparing iridium-based films using the organometallic compound are provided.The organometallic iridium compound represented by the formula (1) ##STR00001## (example of specific compound: (ethylcyclopentadienyl)bis(ethylene)iridium) is obtained by reacting a compound represented by the formula (4) ##STR00002## with a compound represented by the formula (2) or (3) ##STR00003## An iridium-based film is prepared using the compound as a precursor. In the formulae, R.sub.1 represents hydrogen atom or a lower alkyl group; R.sub.2 represents a lower alkyl group; X represents a halogen atom; and M represents an alkali metal.