期刊
INORGANIC CHEMISTRY
卷 54, 期 22, 页码 10656-10666出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.inorgchem.5b01463
关键词
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资金
- European Research Council [ERC-2011-StG-279549, ERC-2009-StG-239910]
- Netherlands Fund for Technology and Science STW [11059]
- Ministry of Education, Culture and Science [024.001.035]
- Ubbo Emmius Fund of the University of Groningen
- MINECO of Spain [CTQ2012-37420-C02-01/BQU, CSD2010-00065]
- Generalitat de Catalunya [2009SGR637]
- Generalitat de Catalunya (ICREA Academia Award)
- COST action [CM1003]
The spectroscopic, electrochemical, and crystallographic characterization of [((Me,H)PyTACN)-Ni-II(CH3CN)(2)](OTf)(2) (1) ((Me,H)PyTACN = 1-(2-pyridylmethyl)-4,7-dimethyl-1,4,7-triazacyclononane, OTf = CF3SO3) is described together with its reactivity with NaOCl. 1 catalyzes the chlorination of alkanes with NaOCl, producing only a trace amount of oxygenated byproducts. The reaction was monitored spectroscopically and by high resolution electrospray-mass spectrometry (ESI-MS) with the aim to elucidate mechanistic aspects. NaOCl reacts with 1 in acetonitrile to form the transient species [(L)Ni-II-OCl(S)](+) (A) (L = (Me,H)PyTACN, S = solvent), which was identified by ESI-MS. UV/vis absorption, electron paramagnetic resonance, and resonance Raman spectroscopy indicate that intermediate A decays to the complex [(L)Ni-II-OH(S)(2+) (B) presumably through homolytic cleavage of the O-Cl bond, which liberates Cl-center dot atom. Hydrolysis of acetonitrile to acetic acid under the applied conditions results in the formation of [(L)Ni-III-OOCCH3(S)](2+) (C), which undergoes subsequent reduction to [(L)Ni-II-OOCCH3(S)](2+) (D), presumably via reaction with OCl- or ClO2-. Subsequent addition of NaOCl to [(L)Ni-II-OOCCH3(S)](+) (D) regenerates RL)Ni-III-OH(S)](2+) (B) to a much greater extent and at a faster rate. Addition of acids such as acetic and triflic acid enhances the rate and extent of formation of [(L)Ni-III-OH(S)](2+) (B) from 1, suggesting that O-Cl homolytic cleavage is accelerated by protonation. Overall, these reactions generate Cl-center dot atoms and ClO2 in a catalytic cycle where the nickel center alternates between Ni(II) and Ni(III). Chlorine atoms in turn react with the C-H bonds of alkanes, forming alkyl radicals that are trapped by Cl-center dot to form alkyl chlorides.
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