REACTION-KINETICS OF COORDINATIVELY UNSATURATED IRON CARBONYLS FORMED ON GAS-PHASE EXCIMER LASER PHOTOLYSIS OF FE(CO)5

The reactions of species produced on gas-phase excimer laser photolysis of Fe(CO)5 have been followed by transient infrared spectroscopy employing a diode laser probe. The initial photoproducts formed on 193-nm photolysis are identified as Fe(CO)2 and a product that is most likely Fe(CO). Both Fe(CO)2 and Fe(CO)3 are produced on 248-nm photolysis. Photolysis at 351 nm leads to the production of both Fe(CO)3 and Fe(CO)4. Species best assigned as excited states of Fe(CO)3 and Fe(CO)4 are observed to form as initial photoproducts following 248- and 351-nm photolysis, respectively. The magnitudes of the rate constants for reaction of the various coordinatively unsaturated metal carbonyls formed in this study with parent Fe(CO)5 or CO (summarized in Table I) are consistent with the hypothesis that spin-allowed reactions will be rapid while spin-disallowed reactions will be considerably slower. To provide further data in testing this hypothesis, the reaction of Fe(CO)4 with both O2 and H-2 has been measured.