Polyoxoanion- and Tetrabutylammonium-Stabilized, Near-Monodisperse, 40 ± 6 Å Rh(0)∼1500to Rh(0)∼3700Nanoclusters: Synthesis, Characterization, and Hydrogenation Catalysis
Source abstract
Abstract
Polyoxoanion- and tetrabutylammonium-stabilized near-monodisperse 40 ± 6 Å Rh(0) ∼ 1500 to Rh(0) ∼ 3700 nanoclusters have been prepared by hydrogen reduction, in acetone, of a polyoxoanion-supported Rh(I) complex, [( n -C 4 H 9 ) 4 N] 5 Na 3 [(1,5-COD)Rh·P 2 W 15 Nb 3 O 62 ], a reaction in which the resultant Rh(0) nanoclusters serve as a cyclohexene hydrogenation catalyst. The Rh(0) ∼ 1500 to Rh(0) ∼ 3700 nanoclusters are isolated as a black powder that can be fully redispersed in non-aqueous solvents such as acetonitrile; they have been characterized by transmission electron microscopy, energy dispersive spectroscopy, electron diffraction, UV−vis spectroscopy, and elemental analysis. Ion-exchange chromatography shows that the isolated Rh(0) nanoclusters are stabilized by the adsorption of the polyoxoanion onto their outer surfaces. Hydrogen gas-uptake stoichiometry, in combination with quantitative kinetic evidence, is presented, indicating that the nanoclusters grow by the slow nucleation, then fast autocatalytic surface-growth, mechanism recently reported for their Ir(0) ∼ 300 congeners. The isolated Rh(0) nanoclusters are also active cyclohexene hydrogenation catalysts in solution; Hg(0) poisoning experiments confirm that the Rh(0) nanoclusters are the active catalyst. These are only the second example of polyoxoanion-stabilized transition-metal nanoclusters; their availability, as well as the record stability and catalytic lifetime in solution of polyoxoanion-stabilized transition-metal nanoclusters, makes possible both fundamental and practical investigations of Rh(0) metal−particle catalysis in solution.
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Research context
OpenAlex topics: Nanocluster Synthesis and Applications · Quantum Dots Synthesis And Properties · Advanced Nanomaterials in Catalysis
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Affiliations
Colorado State University, Department of Chemistry, Fort Collins, Colorado 80523
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