No abstract

We report measurements of the primary photochemical fragmentation of iron pentacarbonyl into the species Fe(CO)5-n(1⩽n⩽4) resulting from one-photon absorption at 352, 248, and 193 nm. We have observed a high degree of fragmentation, with increasing fragmentation at shorter wavelengths. We believe that the fragmentation results from sequential loss of carbon monoxide with a high degree of retention of internal excitation in the resulting Fe(CO)5-n fragments. A surprisal analysis shows that the fragmentation pattern is highly nonstatistical. The variation in fragmentation with input energy is consistent with a statistical model in which the vibrational space is restricted to a single vibrational degree of freedom. Alternatively, dissociation may proceed through a sequence of electronically excited fragments. Both pictures are consistent with a plausible molecular orbital argument.

Articles you may be interested inTime-resolved infrared diode laser spectroscopy of the ν1 band of the iron carbonyl radical (FeCO) produced by the ultraviolet photolysis of Fe(CO)5We have studied the photolysis of mixtures of Fe(CO), and PF J with a KrF laser operating at 248 nm. The product yields of Fe(COh(PFJh. Fe(CO),(PFJh. and Fe(CO).PF J have been measured as a function of laser fluence and mixture composition. A simple kinetic model appears to explain semiquantitatively the observed dependence of product yield upon mixture composition. This model has allowed us to determine that the primary photochemical yields at 248 nm for the fragments Fe(COh, Fe(CO),. and Fe(CO). over the fluence range 0.1-200 mJ/cm 2 are 0.55. 0.35. and 0.10. respectively. independent of laser fluence. This fragmentation results from a simple one-photon absorption process. We have found that CO ligands are exchanged readily in collisions of the above fragments with Fe(CO),. with a bimolecular rate constant relative to that for trapping by PF J of kMlkT = 4. We have also found that these primary photofragments react with Fe(CO), to form unobserved products with a rate constant (relative to that for trapping by PF J ) of kQlkT = 7.

Die Bestrahlung von Mischungen aus Cr(CO)6 und 1‐Buten in der Gasphase mit einen KrF‐Laser (248 nm) führt im Gegensatz zu Ergebnissen in Lösung zur Isomerisierung von 1‐Buten zu 2‐Buten.