A Density-Functional Theory Based Study on the 16O/18O-Exchange Reactions of the Prototype Iron-Oxygen Compounds FeO+ and FeOH+ with H218O in the Gas Phase

Abstract

The mechanism of the degenerate 16O/18O exchange in the reactions of FeO+ and FeOH+ with water is examined by density functional theory. Based on previous experimental work (Chem. Eur. J. 1999, 5, 1176), two possible reaction pathways are investigated for both systems. The first mechanism consists of one (for FeOH+ + H2O) or two (for FeO+ + H2O) 1,3-hydrogen migrations from one oxygen atom to the other; the iron atom is not directly involved in these OH bond activations. The second route comprises a series of two (for FeOH+ + H2O) or four (for FeO+ + H2O) 1,2-hydrogen migration steps which involve the intermediate formations of metal-hydrogen bonds. Both mechanisms are evaluated under consideration of the respective low- and high spin potential-energy surfaces. The computational results show a clear preference for the 1,3-routes occurring on the respective high-spin surfaces bypassing the intermediacy of high-valent iron compounds having FeH bonds.