SF6-Sensitized Infrared Photodecomposition of Fe(CO)5

Article abstract of DOI:10.1021/ja00189a007

The SF6-sensitized infrared photodecomposition of Fe(CO)5 induced by a transversely excited atmospheric (TEA) CO2 laser has been studied.The decomposition of Fe(CO)5 proceeds via sequential decarbonylation after thermal equilibrium is attained through collisional V-V and V-T/R processes.Fe(CO)4(PF3) is formed as a dominant product at lower conversion in a mixture of SF6-Fe(CO)5- PF3, which indicates that the rate-determining process is the first decarbonylation of excited Fe(CO)5 into Fe(CO)4 and CO, and that Fe(CO)4 is trapped by PF3 to yield Fe(CO)4(PF3).In addition, Fe(CO)3(PF3)2, Fe(CO)2(PF3)3, and Fe(CO)(PF3)4 are formed progressively with increasing conversion of Fe(CO)5.The higher PF3-substituted iron complexes are formed by repeated series of thermal excitation, decarbonylation, and trapping by PF3.Final products are CO and iron particles, following the shot by shot stoichiometry of Fe(CO)5 --> Fe + 5CO.The iron particles are found to by γ-iron or austenite, (Fe-C)4F, including 0.75 wt percent carbon which has a mean particle size of 80 Angstroem and a face-centered-cubic structure.Variations of the decomposition probability by changing the irradiation parameters are qualitatively explained by changes of kinetic temperture in irradiated volume.The decomposition mechanism in SF6-sensitized infrared photolysis is compared with those in conventional pyrolysis, infrared multiple-photon decomposition, and uV photolysis.