Synthesis and characterization of mononuclear ruthenium(III) pyridylamine complexes and mechanistic insights into their catalytic alkane functionalization with m-chloroperbenzoic acid

Takahiko Kojima, Ken Ichi Hayashi, Shin Ya Iizuka, Fumito Tani, Yoshinori Naruta, Masaki Kawano, Yuji Ohashi, Yuichirou Hirai, Kei Ohkubo, Yoshihisa Matsuda, Shunichi Fukuzumi

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Abstract

A series of mononuclear RuIII complexes [RuCl 2(L)]+, where L is tris(2-pyridylmethyl)amine (TPA) or one of four TPA derivatives as tetradentate ligand, were prepared and characterized by spectroscopic methods, X-ray crystallography, and electrochemical measurements. The geometry of a RuIII complex having a non-three-fold-symmetric TPA ligand bearing one dimethylnicotinamide moiety was determined to show that the nicotine moiety resides trans to a pyridine group, but not to the chlorido ligand. The substituents of the TPA ligands were shown to regulate the redox potential of the ruthenium center, as indicated by a linear Hammett plot in the range of 200 mV for RuIII/RuIV couples with a relatively large ρ value (+ 0.150). These complexes act as effective catalysts for alkane functionalization in acetonitrile with m-chloroper-benzoic acid (mCPBA) as terminal oxidant at room temperature. They exhibited fairly good reactivity for oxidation of cyclohexane (C-H bond energy 94 kcal mol-1), and the reactivity can be altered significantly by the electronic effects of substituents on TPA ligands in terms of initial rates and turn-over numbers. Catalytic oxygenation of cyclohexane by a Ru III complex with 16O-mCPBA in the presence of H 218O gave 18O-labeled cyclohexanol with 100% inclusion of the 18O atom from the water molecule. Resonance Raman spectra under catalytic conditions without the substrate indicate formation of a RuIV=O intermediate with lower bonding energy. Kinetic isotope effects (KIEs) in the oxidation of cyclohexane suggest that hydrogen abstraction is the rate-determining step and the KIE values depend on the substituents of the TPA ligands. Thus, the reaction mechanism of catalytic cyclohexane oxygenation depends on the electronic effects of the ligands.

Original languageEnglish
Pages (from-to)8212-8222
Number of pages11
JournalChemistry - A European Journal
Volume13
Issue number29
DOIs
Publication statusPublished - Oct 24 2007

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Alkanes
Ruthenium
Paraffins
Ligands
Cyclohexane
Acids
Benzoic Acid
Oxygenation
Benzoic acid
Isotopes
Bearings (structural)
Cyclohexanols
Nicotine
Oxidation
Kinetics
X ray crystallography
3-chloroperbenzoic acid
Acetonitrile
Oxidants
Pyridine

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Organic Chemistry

Cite this

Synthesis and characterization of mononuclear ruthenium(III) pyridylamine complexes and mechanistic insights into their catalytic alkane functionalization with m-chloroperbenzoic acid. / Kojima, Takahiko; Hayashi, Ken Ichi; Iizuka, Shin Ya; Tani, Fumito; Naruta, Yoshinori; Kawano, Masaki; Ohashi, Yuji; Hirai, Yuichirou; Ohkubo, Kei; Matsuda, Yoshihisa; Fukuzumi, Shunichi.

In: Chemistry - A European Journal, Vol. 13, No. 29, 24.10.2007, p. 8212-8222.

Research output: Contribution to journalArticle

Kojima, Takahiko ; Hayashi, Ken Ichi ; Iizuka, Shin Ya ; Tani, Fumito ; Naruta, Yoshinori ; Kawano, Masaki ; Ohashi, Yuji ; Hirai, Yuichirou ; Ohkubo, Kei ; Matsuda, Yoshihisa ; Fukuzumi, Shunichi. / Synthesis and characterization of mononuclear ruthenium(III) pyridylamine complexes and mechanistic insights into their catalytic alkane functionalization with m-chloroperbenzoic acid. In: Chemistry - A European Journal. 2007 ; Vol. 13, No. 29. pp. 8212-8222.
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AU - Tani, Fumito

AU - Naruta, Yoshinori

AU - Kawano, Masaki

AU - Ohashi, Yuji

AU - Hirai, Yuichirou

AU - Ohkubo, Kei

AU - Matsuda, Yoshihisa

AU - Fukuzumi, Shunichi

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