Polyoxoanion- and tetrabutylammonium-stabilized, near-monodisperse, 40 {+-} 6 {angstrom} Rh(0){sub {approximately}1500} to Rh(0){sub {approximately}3700} nanoclusters: Synthesis, characterization, and hydrogenation catalysis
- Colorado State Univ., Fort Collins, CO (United States). Dept. of Chemistry
Polyoxoanion- and tetrabutylammonium-stabilized near-monodisperse 40 {+-} 6 {angstrom} Rh(0){sub {approximately}1500} to Rh(0){sub {approximately}3700} nanoclusters have been prepared by hydrogen reduction, in acetone, of a polyoxoanion-supported Rh(I) complex, [(n-C{sub 4}H{sub 9}){sub 4}N]{sub 5}Na{sub 3}[(1,5-COD)Rh{center_dot}P{sub 2}W{sub 15}Nb{sub 3}O{sub 62}], a reaction in which the resultant Rh(0) 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){sub {approximately}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.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG06-89ER13998
- OSTI ID:
- 347499
- Journal Information:
- Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 4 Vol. 11; ISSN 0897-4756; ISSN CMATEX
- Country of Publication:
- United States
- Language:
- English
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