Reaction Pathways for the Oxidation of Methanol to Formaldehyde by an Iron−Oxo Species YoshizawaKazunari KagawaYoshihisa 2000 The reaction mechanism and energetics for the conversion of methanol to formaldehyde by an iron−oxo species, FeO<sup>+</sup>, is investigated. Three competitive reaction pathways for the catalytic reaction are analyzed from DFT computations at the B3LYP level of theory. In Path 1, the H atom of the OH group of methanol is first abstracted by the oxo group of FeO<sup>+</sup> via a four-centered transition state (<b>TS</b><b><sub>1</sub></b><b><sub>-</sub></b><b><sub>1</sub></b>) leading to the intermediate complex HO−Fe<sup>+</sup>−OCH<sub>3</sub>, and after that one of the H atoms of the OCH<sub>3</sub> group is shifted to the OH ligand via a five-centered transition state (<b>TS</b><b><sub>1</sub></b><b><sub>-</sub></b><b><sub>2</sub></b>) to form the final product complex H<sub>2</sub>O−Fe<sup>+</sup>−OCH<sub>2</sub>. In Path 2, one of the H atoms of the CH<sub>3</sub> group of methanol is abstracted by the oxo group via a five-centered transition state (<b>TS</b><b><sub>2</sub></b><b><sub>-</sub></b><b><sub>1</sub></b>) leading to the intermediate complex HO−Fe<sup>+</sup>−OHCH<sub>2</sub>, and then the H atom of the OHCH<sub>2</sub> group is shifted to the OH ligand via a four-centered transition state (<b>TS</b><b><sub>2</sub></b><b><sub>-</sub></b><b><sub>2</sub></b>) to give the product complex. Unlike Paths 1 and 2, which involve a hydrogen shift, the first step in Path 3 involves a methyl migration that takes place via a four-centered transition state (<b>TS</b><b><sub>3</sub></b><b><sub>-</sub></b><b><sub>1</sub></b>) resulting in the formation of the intermediate complex HO−Fe<sup>+</sup>−OCH<sub>3</sub> and the second half of Path 3 is identical to that of Path 1. From B3LYP computations, Path 1 and Path 2 are competitive in energy and Path 3 is unlikely from the energetic viewpoint. Kinetic isotope effects (<i>k</i><sub>H</sub>/<i>k</i><sub>D</sub>) for the electronic processes of <b>TS</b><b><sub>1</sub></b><b><sub>-</sub></b><b><sub>1</sub></b>, <b>TS</b><b><sub>2</sub></b><b><sub>-</sub></b><b><sub>1</sub></b>, and <b>TS</b><b><sub>3</sub></b><b><sub>-</sub></b><b><sub>1</sub></b> are computed and analyzed.