Control of chemoselectivity in hydrogenations of substituted nitro- and cyano-aromatics by cluster-derived ruthenium nanocatalysts

Indra, Arindam ; Maity, Niladri ; Maity, Prasenjit ; Bhaduri, Sumit ; Lahiri, Goutam Kumar (2011) Control of chemoselectivity in hydrogenations of substituted nitro- and cyano-aromatics by cluster-derived ruthenium nanocatalysts Journal of Catalysis, 284 (2). pp. 176-183. ISSN 0021-9517

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Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/j.jcat.2011.09.020

Abstract

Catalyst precursors 1 and 2, made by ion-pairing [H3Ru4(CO)12]- with NR4+groups of functionalized MCM-41 and water-soluble poly(diallyldimethylammonium chloride), PDADMAC, respectively, have been evaluated for the chemoselective hydrogenation of nitro- and cyano-benzaldehydes. They are found to be inert toward -NO2 and -CN groups, but active for the reduction of -CHO and >C=C< functionalities. Thus, 3, 4-nitrobenzaldehyde, nitrostyrene, and 3-cyanobenzaldehyde are hydrogenated with full selectivity to the corresponding nitrobenzylalcohols, 1-ethyl-3-nitrobenzene, and 3-cynaobenzylalcohol, respectively. No such chemoselectivity is observed either with PDADMAC-RuCl4 (3) or with (5%)Ru-Al2O3, where both the functional groups are hydrogenated. Kinetic analyses have been carried out for the hydrogenation of 4-nitrobenzaldehyde with 2. Existence of an induction time and two competitive equilibriums followed by the product-forming rate-determining step are inferred from the empirically derived rate expression. The kinetic results, structural evidences, and previous work strongly suggest that the observed chemoselectivity is probably a result of the absence of multiple crystal planes, differing in Miller indices, in the cluster-derived catalysts.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Supported Catalysts; Clusters; Chemoselectivity; Hydrogenation; Nitro-benzaldehydes; Cyano-benzaldehydes
ID Code:88353
Deposited On:29 Mar 2012 14:31
Last Modified:22 Jul 2012 14:35

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