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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

Controlling Catalytic Activity and Selectivity for Partial Hydrogenation by Tuning the Environment Around Active Sites in Iridium Complexes Bonded to Supports

Melike Babucci, Chia-Yu Fang, Jorge E Perez-Aguilar, Adam S Hoffman, Alexey Boubnov, Erjia Guan, Simon R Bare, Bruce C Gates, Alper Uzun

Chem Sci. 2019 Jan 9;10(9):2623-2632.

PMID: 30996978

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.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP879866747	1-(3-Cyanopropyl)-3-methylimidazolium dicyanamide		879866-74-7	Price

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