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Serna P, Gates BC. Molecular metal catalysts on supports: organometallic chemistry meets surface science. Acc Chem Res 2014; 47:2612-20. [PMID: 25036259 DOI: 10.1021/ar500170k] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Recent advances in the synthesis and characterization of small, essentially molecular metal complexes and metal clusters on support surfaces have brought new insights to catalysis and point the way to systematic catalyst design. We summarize recent work unraveling effects of key design variables of site-isolated catalysts: the metal, metal nuclearity, support, and other ligands on the metals, also considering catalysts with separate, complementary functions on supports. The catalysts were synthesized with the goal of structural simplicity and uniformity to facilitate incisive characterization. Thus, they are essentially molecular species bonded to porous supports chosen for their high degree of uniformity; the supports are crystalline aluminosilicates (zeolites) and MgO. The catalytic species are synthesized in reactions of organometallic precursors with the support surfaces; the precursors include M(L)2(acetylacetonate)1-2, with M = Ru, Rh, Ir, or Au and the ligands L = C2H4, CO, or CH3. Os3(CO)12 and Ir4(CO)12 are used as precursors of supported metal clusters, and some such catalysts are made by ship-in-a-bottle syntheses to trap the clusters in zeolite cages. The simplicity and uniformity of the supported catalysts facilitate precise structure determinations, even in reactive atmospheres and during catalysis. The methods of characterizing catalysts in reactive atmospheres include infrared (IR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and nuclear magnetic resonance (NMR) spectroscopies, and complementary methods include density functional theory and atomic-resolution aberration-corrected scanning transmission electron microscopy for imaging of individual metal atoms. IR, NMR, XANES, and microscopy data demonstrate the high degrees of uniformity of well-prepared supported species. The characterizations determine the compositions of surface metal complexes and clusters, including the ligands and the metal-support bonding and structure, which identify the supports as ligands with electron-donor properties that influence reactivity and catalysis. Each of the catalyst design variables has been varied independently, illustrated by mononuclear and tetranuclear iridium on zeolite HY and on MgO and by isostructural rhodium and iridium (diethylene or dicarbonyl) complexes on these supports. The data provide examples resolving the roles of the catalyst design variables and place the catalysis science on a firm foundation of organometallic chemistry linked with surface science. Supported molecular catalysts offer the advantages of characterization in the absence of solvents and with surface-science methods that do not require ultrahigh vacuum. Families of supported metal complexes have been made by replacement of ligands with others from the gas phase. Spectroscopically identified catalytic reaction intermediates help to elucidate catalyst performance and guide design. The methods are illustrated for supported complexes and clusters of rhodium, iridium, osmium, and gold used to catalyze reactions of small molecules that facilitate identification of the ligands present during catalysis: alkene dimerization and hydrogenation, H-D exchange in the reaction of H2 with D2, and CO oxidation. The approach is illustrated with the discovery of a highly active and selective MgO-supported rhodium carbonyl dimer catalyst for hydrogenation of 1,3-butadiene to give butenes.
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Dixon DA, Katz A, Arslan I, Gates BC. Beyond Relationships Between Homogeneous and Heterogeneous Catalysis. Catal Letters 2014. [DOI: 10.1007/s10562-014-1332-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Martinez-Macias C, Xu P, Hwang SJ, Lu J, Chen CY, Browning ND, Gates BC. Iridium Complexes and Clusters in Dealuminated Zeolite HY: Distribution between Crystalline and Impurity Amorphous Regions. ACS Catal 2014. [DOI: 10.1021/cs5006426] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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104
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Kistler JD, Chotigkrai N, Xu P, Enderle B, Praserthdam P, Chen CY, Browning ND, Gates BC. A Single-Site Platinum CO Oxidation Catalyst in Zeolite KLTL: Microscopic and Spectroscopic Determination of the Locations of the Platinum Atoms. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201403353] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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105
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Kistler JD, Chotigkrai N, Xu P, Enderle B, Praserthdam P, Chen CY, Browning ND, Gates BC. A Single-Site Platinum CO Oxidation Catalyst in Zeolite KLTL: Microscopic and Spectroscopic Determination of the Locations of the Platinum Atoms. Angew Chem Int Ed Engl 2014; 53:8904-7. [DOI: 10.1002/anie.201403353] [Citation(s) in RCA: 230] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 04/30/2014] [Indexed: 11/08/2022]
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Okrut A, Runnebaum RC, Ouyang X, Lu J, Aydin C, Hwang SJ, Zhang S, Olatunji-Ojo OA, Durkin KA, Dixon DA, Gates BC, Katz A. Selective molecular recognition by nanoscale environments in a supported iridium cluster catalyst. NATURE NANOTECHNOLOGY 2014; 9:459-465. [PMID: 24747837 DOI: 10.1038/nnano.2014.72] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 03/12/2014] [Indexed: 06/03/2023]
Abstract
The active sites of enzymes are contained within nanoscale environments that exhibit exquisite levels of specificity to particular molecules. The development of such nanoscale environments on synthetic surfaces, which would be capable of discriminating between molecules that would nominally bind in a similar way to the surface, could be of use in nanosensing, selective catalysis and gas separation. However, mimicking such subtle behaviour, even crudely, with a synthetic system remains a significant challenge. Here, we show that the reactive sites on the surface of a tetrairidium cluster can be controlled by using three calixarene-phosphine ligands to create a selective nanoscale environment at the metal surface. Each ligand is 1.4 nm in length and envelopes the cluster core in a manner that discriminates between the reactivities of the basal-plane and apical iridium atoms. CO ligands are initially present on the clusters and can be selectively removed from the basal-plane sites by thermal dissociation and from the apical sites by reactive decarbonylation with the bulky reactant trimethylamine-N-oxide. Both steps lead to the creation of metal sites that can bind CO molecules, but only the reactive decarbonylation step creates vacancies that are also able to bond to ethylene, and catalyse its hydrogenation.
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Serna P, Yardimci D, Kistler JD, Gates BC. Formation of supported rhodium clusters from mononuclear rhodium complexes controlled by the support and ligands on rhodium. Phys Chem Chem Phys 2014; 16:1262-70. [DOI: 10.1039/c3cp53057d] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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108
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Che M, Ertl G, Gates BC, Hadjiivanov K. Helmut Knözinger. ADVANCES IN CATALYSIS 2014. [DOI: 10.1016/b978-0-12-800127-1.10000-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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109
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Khabuanchalad S, Wittayakun J, Lobo-Lapidus RJ, Stoll S, Britt RD, Gates BC. Formation of MgO-supported manganese carbonyl complexes by chemisorption of Mn(CO)5CH3. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:6279-6286. [PMID: 23679854 DOI: 10.1021/la303269h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
MgO-supported manganese carbonyl complexes were prepared by chemical vapor deposition of Mn(CO)5CH3 on partially dehydroxylated, high-area MgO powder. X-ray absorption spectra identify the resultant surface species, on average, as Mn(CO)4(Os)2 (where the two oxygen ligands are part of the MgO surface), and infrared spectra show that the chemisorption results from the reaction of Mn(CO)5CH3 with OH groups of the MgO surface. Electron paramagnetic resonance and X-ray absorption near edge data indicate that the manganese was in a positive oxidation state other than +2, but the value is not determined, and the IR spectra indicate the presence of a mixture of manganese carbonyls. Extended X-ray absorption fine structure spectra determine the average Mn-CO bond distance to be 1.87 Å and the average Mn-O bond distance to be 2.12 Å. The surface complex was found to be stable in O2 at room temperature.
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Aydin C, Kulkarni A, Chi M, Browning ND, Gates BC. Three-Dimensional Structural Analysis of MgO-Supported Osmium Clusters by Electron Microscopy with Single-Atom Sensitivity. Angew Chem Int Ed Engl 2013; 52:5262-5. [DOI: 10.1002/anie.201300238] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Indexed: 11/05/2022]
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111
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Aydin C, Kulkarni A, Chi M, Browning ND, Gates BC. Three-Dimensional Structural Analysis of MgO-Supported Osmium Clusters by Electron Microscopy with Single-Atom Sensitivity. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201300238] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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112
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Browning ND, Aydin C, Lu J, Kulkarni A, Okamoto NL, Ortalan V, Reed BW, Uzun A, Gates BC. QuantitativeZ-Contrast Imaging of Supported Metal Complexes and Clusters-A Gateway to Understanding Catalysis on the Atomic Scale. ChemCatChem 2013. [DOI: 10.1002/cctc.201200872] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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113
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Lu J, Martinez-Macias C, Aydin C, Browning ND, Gates BC. Zeolite-supported bimetallic catalyst: controlling selectivity of rhodium complexes by nearby iridium complexes. Catal Sci Technol 2013. [DOI: 10.1039/c3cy00113j] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Gates BC. Supported gold catalysts: new properties offered by nanometer and sub-nanometer structures. Chem Commun (Camb) 2013; 49:7876-7. [DOI: 10.1039/c3cc44942d] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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115
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Kistler JD, Serna P, Gates BC. MgO-supported bimetallic catalysts consisting of segregated, essentially molecular rhodium and osmium species. Dalton Trans 2013; 42:12626-32. [DOI: 10.1039/c3dt50440a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Yardimci D, Serna P, Gates BC. Surface-Mediated Synthesis of Dimeric Rhodium Catalysts on MgO: Tracking Changes in the Nuclearity and Ligand Environment of the Catalytically Active Sites by X-ray Absorption and Infrared Spectroscopies. Chemistry 2012. [DOI: 10.1002/chem.201202514] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Lu J, Aydin C, Browning ND, Wang L, Gates BC. Sinter-Resistant Catalysts: Supported Iridium Nanoclusters with Intrinsically Limited Sizes. Catal Letters 2012. [DOI: 10.1007/s10562-012-0928-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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120
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Yardimci D, Serna P, Gates BC. Tuning Catalytic Selectivity: Zeolite- and Magnesium Oxide-Supported Molecular Rhodium Catalysts for Hydrogenation of 1,3-Butadiene. ACS Catal 2012. [DOI: 10.1021/cs300475c] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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121
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Lu J, Aydin C, Browning ND, Gates BC. Oxide- and zeolite-supported isostructural Ir(C2H4)2 complexes: molecular-level observations of electronic effects of supports as ligands. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:12806-12815. [PMID: 22861660 DOI: 10.1021/la302522a] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Zeolite Hβ- and γ-Al(2)O(3)-supported mononuclear iridium complexes were synthesized by the reaction of Ir(C(2)H(4))(2)(acac) (acac is acetylacetonate) with each of the supports. The characterization of the surface species by extended X-ray absorption fine structure (EXAFS) and infrared (IR) spectroscopies demonstrated the removal of acac ligands during chemisorption, leading to the formation of essentially isostructural Ir(C(2)H(4))(2) complexes anchored to each support by two Ir-O(support) bonds. Atomic-resolution aberration-corrected scanning transmission electron microscopy (STEM) images confirm the spectra, showing only isolated Ir atoms on the supports with no evidence of iridium clusters. These samples, together with previously reported Ir(C(2)H(4))(2) complexes on zeolite HY, zeolite HSSZ-53, and MgO supports, constitute a family of isostructural supported iridium complexes. Treatment with CO led to the replacement of the ethylene ligands on iridium with CO ligands, and the ν(CO) frequencies of these complexes and white line intensities in the X-ray absorption spectra at the Ir L(III) edge show that the electron density on iridium increases in the following order on these supports: zeolite HY < zeolite Hβ < zeolite HSSZ-53 ≪ γ-Al(2)O(3) < MgO. The IR spectra of the iridium carbonyl complexes treated in flowing C(2)H(4) show that the CO ligands were replaced by C(2)H(4), with the average number of C(2)H(4) groups per Ir atom increasing as the amount of iridium was increasingly electron-deficient. In contrast to the typical supported catalysts incorporating metal clusters or particles that are highly nonuniform, the samples reported here, incorporating uniform isostructural iridium complexes, provide unprecedented opportunities for a molecular-level understanding of how supports affect the electronic properties, reactivities, and catalytic properties of supported metal species.
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Nimmanwudipong T, Aydin C, Lu J, Runnebaum RC, Brodwater KC, Browning ND, Block DE, Gates BC. Selective Hydrodeoxygenation of Guaiacol Catalyzed by Platinum Supported on Magnesium Oxide. Catal Letters 2012. [DOI: 10.1007/s10562-012-0884-3] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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123
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Bayram E, Lu J, Aydin C, Uzun A, Browning ND, Gates BC, Finke RG. Mononuclear Zeolite-Supported Iridium: Kinetic, Spectroscopic, Electron Microscopic, and Size-Selective Poisoning Evidence for an Atomically Dispersed True Catalyst at 22 °C. ACS Catal 2012. [DOI: 10.1021/cs300366w] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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Aydin C, Kulkarni A, Chi M, Browning ND, Gates BC. Atomically Resolved Site-Isolated Catalyst on MgO: Mononuclear Osmium Dicarbonyls formed from Os3(CO)12. J Phys Chem Lett 2012; 3:1865-1871. [PMID: 26292006 DOI: 10.1021/jz300574u] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Supported triosmium clusters, formed from Os3(CO)12 on MgO, were treated in helium at 548 K for 2 h, causing fragmentation of the cluster frame and the formation of mononuclear osmium dicarbonyls. The cluster breakup and the resultant fragmented species were characterized by infrared and X-ray absorption spectroscopies, and the fragmented species were imaged by scanning transmission electron microscopy. The spectra identify the surface osmium complexes as Os(CO)2{Osupport}n (n = 3 or 4) (where the braces denote support surface atoms). The images show site-isolated Os atoms in mononuclear osmium species on MgO. The intensity analysis on the images of the MgO(110) face showed that the Os atoms were located atop Mg columns. This information led to a model of the Os(CO)2 on MgO(110), with the distances approximated as those determined by EXAFS spectroscopy, which are an average over the whole MgO surface; the results imply that these complexes were located at Mg vacancies.
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