Mechanistic insight into catalytic oxidations of organic compounds by ruthenium(iv)-oxo complexes with pyridylamine ligands

Shingo Ohzu, Tomoya Ishizuka, Yuichirou Hirai, Hua Jiang, Miyuki Sakaguchi, Takashi Ogura, Shunichi Fukuzumi, Takahiko Kojima

Research output: Contribution to journalArticlepeer-review

73 Scopus citations

Abstract

A series of Ru(iv)-oxo complexes (4-6) were synthesized from the corresponding Ru(ii)-aqua complexes (1-3) and fully characterized by 1H NMR and resonance Raman spectroscopies, and ESI-MS spectrometry. Based on the diamagnetic character confirmed by the 1H NMR spectroscopy in D2O, the spin states of 5 and 6 were determined to be S = 0 in the d4 configuration, in sharp contrast to that of 4 being in the S = 1 spin state. The aqua-complexes 1-3 catalyzed oxidation of alcohols and olefins using (NH4)2[CeIV(NO 3)6] (CAN) as an electron-transfer oxidant in acidic aqueous solutions. Comparison of the reactivity of electrochemically generated oxo-complexes (4-6) was made in the light of kinetic analyses for oxidation of 1-propanol and a water-soluble ethylbenzene derivative. The oxo complexes (4-6) exhibited no significant difference in the reactivity for the oxidation reactions, judging from the similar catalytic rates and the activation parameters. The slight difference observed in the reaction rates can be accounted for by the difference in the reduction potentials of the oxo-complexes, but the spin states of the oxo-complexes have hardly affected the reactivity. The activation parameters and the kinetic isotope effects (KIE) observed for the oxidation reactions of methanol indicate that the oxidation reactions of alcohols with the RuIVO complexes proceed via a concerted proton-coupled electron transfer mechanism.

Original languageEnglish
Pages (from-to)3421-3431
Number of pages11
JournalChemical Science
Volume3
Issue number12
DOIs
StatePublished - Dec 2012

Fingerprint

Dive into the research topics of 'Mechanistic insight into catalytic oxidations of organic compounds by ruthenium(iv)-oxo complexes with pyridylamine ligands'. Together they form a unique fingerprint.

Cite this