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Oxygen Atom Transfer from a trans-Dioxoruthenium(VI) Complex to Nitric Oxide

Authors

  • Dr. Wai-Lun Man,

    1. Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (P.R. China), Fax: (+852) 34420522
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  • Dr. William W. Y. Lam,

    1. Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (P.R. China), Fax: (+852) 34420522
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  • Siu-Mui Ng,

    1. Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (P.R. China), Fax: (+852) 34420522
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  • Wenny Y. K. Tsang,

    1. Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (P.R. China), Fax: (+852) 34420522
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  • Prof. Tai-Chu Lau

    Corresponding author
    1. Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (P.R. China), Fax: (+852) 34420522
    • Department of Biology and Chemistry and Institute of Molecular Functional Materials, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong (P.R. China), Fax: (+852) 34420522
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Abstract

In aqueous acidic solutions trans-[RuVI(L)(O)2]2+ (L=1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane) is rapidly reduced by excess NO to give trans-[Ru(L)(NO)(OH)]2+. When ≤1 mol equiv NO is used, the intermediate RuIV species, trans-[RuIV(L)(O)(OH2)]2+, can be detected. The reaction of [RuVI(L)(O)2]2+ with NO is first order with respect to [RuVI] and [NO], k2=(4.13±0.21)×101M−1 s−1 at 298.0 K. ΔH and ΔS are (12.0±0.3) kcal mol−1 and −(11±1) cal mol−1 K−1, respectively. In CH3CN, ΔH and ΔS have the same values as in H2O; this suggests that the mechanism is the same in both solvents. In CH3CN, the reaction of [RuVI(L)(O)2]2+ with NO produces a blue-green species with λmax at approximately 650 nm, which is characteristic of N2O3. N2O3 is formed by coupling of NO2 with excess NO; it is relatively stable in CH3CN, but undergoes rapid hydrolysis in H2O. A mechanism that involves oxygen atom transfer from [RuVI(L)(O)2]2+ to NO to produce NO2 is proposed. The kinetics of the reaction of [RuIV(L)(O)(OH2)]2+ with NO has also been investigated. In this case, the data are consistent with initial one-electron O transfer from RuIV to NO to produce the nitrito species [RuIII(L)(ONO)(OH2)]2+ (k2>106M−1 s−1), followed by a reaction with another molecule of NO to give [Ru(L)(NO)(OH)]2+ and NO2 (k2=54.7 M−1 s−1).

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