Modeling the Reaction of Fe Atoms with CCl4

Abstract

The reaction of iron atoms with carbon tetrachloride (CCl4) in gas phase was studied using density functional theory. A recent experimental study (Parkinson, G. S.; Dohnálek, Z.; Smith, R. S.; Kay, B. D. J. Phys. Chem. C 2009, 113, 1818) of this reaction, performed by dropping Fe atoms into CCl4 deposited on a cold FeO(111) surface, demonstrates rich chemistry with several products (C2Cl4, C2Cl6, OCCl2, CO, FeCl2, and FeCl3) observed. The reactions of Fe with CCl4 was studied under three stoichiometries, one Fe with one CCl4, one Fe with two CCl4 molecules, and two Fe with one CCl4, modeling the stoichiometric, CCl4-rich, and Fe-rich environments of the experimental work. The electronic structure calculations give insight into the reactions leading to the experimentally observed products, in particular with regard to the formation of FeCl3 and other oxygen containing compounds that are not predicted from the simplest reactive model of successive Cl atom abstractions. They rather suggest that novel Fe−C−Cl containing species are important intermediates in these reactions. The intermediate complexes are formed in highly exothermic reactions, in agreement with the experimentally observed reactivity on the surface at low temperature (30 K). This initial survey of the reactivity of Fe with CCl4 identifies some potential reaction pathways that are important in the effort to use Fe nanoparticles to differentiate harmful pathways that lead to the formation of contaminants like chloroform (CHCl3) from harmless pathways that lead to products such as formate (HCO2−) or carbon oxides in water and soil.