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Issue 9, 2019
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Controlling catalytic activity and selectivity for partial hydrogenation by tuning the environment around active sites in iridium complexes bonded to supports

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Abstract

Single-site Ir(CO)2 complexes bonded to high-surface-area metal oxide supports, SiO2, TiO2, Fe2O3, CeO2, MgO, and La2O3, were synthesized by chemisorption of Ir(CO)2(acac) (acac = acetylacetonate) followed by coating with each of the following ionic liquids (ILs): 1-n-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4], 1-n-butyl-3-methylimidazolium acetate, [BMIM][Ac], and 1-(3-cyanopropyl)-3-methylimidazolium dicyanamide, [CPMIM][DCA]. Extended X-ray absorption fine structure spectroscopy showed that site-isolated iridium was bonded to oxygen atoms of the support. Electron densities on the iridium enveloped by each IL sheath/support combination were characterized by carbonyl infrared spectroscopy of the iridium gem-dicarbonyls and by X-ray absorption near-edge structure data. The electron-donor/acceptor tendencies of both the support and IL determine the activity and selectivity of the catalysts for the hydrogenation of 1,3-butadiene, with electron-rich iridium being selective for partial hydrogenation. The results resolve the effects of the IL and support as ligands; for example, the effect of the IL becomes dominant when the support has a weak electron-donor character. The combined effects of supports and ILs as ligands offer broad opportunities for tuning catalytic properties of supported metal catalysts.

Graphical abstract: Controlling catalytic activity and selectivity for partial hydrogenation by tuning the environment around active sites in iridium complexes bonded to supports

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Publication details

The article was received on 27 Nov 2018, accepted on 08 Jan 2019 and first published on 09 Jan 2019


Article type: Edge Article
DOI: 10.1039/C8SC05287E
Chem. Sci., 2019,10, 2623-2632
  • Open access: Creative Commons BY license
    All publication charges for this article have been paid for by the Royal Society of Chemistry

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    Controlling catalytic activity and selectivity for partial hydrogenation by tuning the environment around active sites in iridium complexes bonded to supports

    M. Babucci, C. Fang, J. E. Perez-Aguilar, A. S. Hoffman, A. Boubnov, E. Guan, S. R. Bare, B. C. Gates and A. Uzun, Chem. Sci., 2019, 10, 2623
    DOI: 10.1039/C8SC05287E

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