Mechanistic study of methanol oxidation by RuIV-oxo complexes

Yoshihito Shiota, Shoya Takahashi, Shingo Ohzu, Tomoya Ishizuka, Takahiko Kojima, Kazunari Yoshizawa

Research output: Contribution to journalArticle

Abstract

The catalytic conversion of methanol to formaldehyde by three kinds of non-porphyrin Ru complexes, RuIVO(TPA) (TPA = tris(2-pyridylmethyl)amine) (1a), RuIVO(6-COO-TPA) (6-COOTPA = 2-(6-carboxyl-pyridyl)methyl-bis(2-pyridylmethyl)amine) (1b), and RuIVO(N4Py) (N4Py = N,N-bis(2-pyridyl-methyl)-N-bis(2-pyridyl)methylamine) (1c), is discussed by using density functional theory (DFT) calculations. There are two possible reaction pathways for the oxidation of methanol to formaldehyde with respect to the first hydrogen abstraction from the methyl group (path 1) and the hydroxyl group (path 2). Path 1 and path 2 involve the hydroxymethyl radical (•CH2OH) and the methoxyl radical (CH3O•), respectively, as an intermediate. DFT calculations demonstrate that the two pathways are energetically comparable in the reactions by the three RuIV-oxo complexes. The reactions with 1a and 1c are initiated by the C-H bond dissociation with activation barriers of 22.2 and 21.4 kcal/mol, respectively, while the reaction with 1b is initiated by the O-H bond dissociation with an activation barrier of 18.1 kcal/mol. However, the calculations showed that the rate-determining step is the H-atom abstraction from the CH3 group of methanol in all the pathways. These results are in good agreement with kinetic analysis of the reactions by the RuIV-oxo complexes, being useful for considering the mechanism of methanol oxidation.

Original languageEnglish
Pages (from-to)417-426
Number of pages10
JournalJournal of Porphyrins and Phthalocyanines
Volume19
Issue number1-3
DOIs
Publication statusPublished - Jan 1 2015

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

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