101
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Dai J, Yao P, Hua N, Yang P, Du Y. Preparation and Characterization of Polymer‐Protected Pt@Pt/Au Core‐Shell Nanoparticles. J DISPER SCI TECHNOL 2007. [DOI: 10.1080/01932690701459488] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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102
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Chotisuwan S, Wittayakun J, Lobo-Lapidus RJ, Gates BC. MgO-supported cluster catalysts with Pt–Ru interactions prepared from Pt3Ru6(CO)21(μ3-H)(μ-H)3. Catal Letters 2007. [DOI: 10.1007/s10562-007-9119-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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103
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Yu KMK, Yeung CMY, Tsang SC. Carbon Dioxide Fixation into Chemicals (Methyl Formate) at High Yields by Surface Coupling over a Pd/Cu/ZnO Nanocatalyst. J Am Chem Soc 2007; 129:6360-1. [PMID: 17465547 DOI: 10.1021/ja0706302] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- K M Kerry Yu
- Surface and Catalysis Research Centre, Department of Chemistry, University of Reading, Reading RG6 6AD, U.K
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104
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Arnold PL, Liddle ST, McMaster J, Jones C, Mills DP. A lanthanide-gallium complex stabilized by the N-heterocyclic carbene group. J Am Chem Soc 2007; 129:5360-1. [PMID: 17411055 DOI: 10.1021/ja0710858] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Polly L Arnold
- School of Chemistry, University of Nottingham, University Park, Nottingham, NG7 2RD, UK.
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105
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Bein T. Host–Guest Interactions in Zeolites and Periodic Mesoporous Materials. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/s0167-2991(07)80806-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023]
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106
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107
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108
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Chotisuwan S, Wittayakun J, Gates BC. Pt3Ru6Clusters Supported on γ-Al2O3: Synthesis from Pt3Ru6(CO)21(μ3-H)(μ-H)3, Structural Characterization, and Catalysis of Ethylene Hydrogenation andn-Butane Hydrogenolysis. J Phys Chem B 2006; 110:12459-69. [PMID: 16800573 DOI: 10.1021/jp057550+] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The supported clusters Pt-Ru/gamma-Al2O3 were prepared by adsorption of the bimetallic precursor Pt3Ru6(CO)21(mu3-H)(mu-H)3 from CH2Cl2 solution onto gamma-Al2O3 followed by decarbonylation in He at 300 degrees C. The resultant supported clusters were characterized by infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies and as catalysts for ethylene hydrogenation and n-butane hydrogenolysis. After adsorption, the nu(CO) peaks characterizing the precursor shifted to lower wavenumbers, and some of the hydroxyl bands of the support disappeared or changed, indicating that the CO ligands of the precursor interacted with support hydroxyl groups. The EXAFS results show that the metal core of the precursor remained essentially unchanged upon adsorption, but there were distortions of the metal core indicated by changes in the metal-metal distances. After decarbonylation of the supported clusters, the EXAFS data indicated that Pt and Ru atoms interacted with support oxygen atoms and that about half of the Pt-Ru bonds were maintained, with the composition of the metal frame remaining almost unchanged. The decarbonylated supported bimetallic clusters reported here are the first having essentially the same metal core composition as that of a precursor metal carbonyl, and they appear to be the best-defined supported bimetallic clusters. The material was found to be an active catalyst for ethylene hydrogenation and n-butane hydrogenolysis under conditions mild enough to prevent substantial cluster disruption.
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Affiliation(s)
- Saowapa Chotisuwan
- School of Chemistry, Suranaree University of Technology, Nakhon Ratchasima, Thailand
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109
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Goda AM, Barteau MA, Chen JG. Correlating Electronic Properties of Bimetallic Surfaces with Reaction Pathways of C2 Hydrocarbons. J Phys Chem B 2006; 110:11823-31. [PMID: 16800484 DOI: 10.1021/jp0554689] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The rate and selectivity of chemical reactions on transition-metal surfaces can be controlled by using different bimetallic combinations. The interaction of bimetallic components leads to a change in the electronic properties of the surface, which in turn produces a change in chemical reactivity. In the current paper, we illustrate the correlation of the electronic properties of bimetallic surfaces with the reaction pathways of C2 hydrocarbons. Density functional theory (DFT) was used to study the binding of hydrogen, ethylene, acetylene, ethyl, and vinyl on monometallic and bimetallic transition-metal surfaces. The binding energies of these species were found to correlate with the d-band centers of these surfaces. The binding energies for hydrogen atoms on bimetallic surfaces were lower than for those on the corresponding parent metal surfaces. This trend was consistent for ethylene and acetylene binding. Comparative studies between acetylene and ethylene revealed that acetylene was more strongly bonded to the monometallic and the bimetallic surfaces than was ethylene. Bond order conservation (BOC) theory was used to calculate the activation barriers for ethyl dehydrogenation to ethylene and vinyl dehydrogenation to acetylene. The activation barriers for these reactions were correlated with the surface d-band center of the substrates.
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Affiliation(s)
- A M Goda
- Center for Catalytic Science and Technology, Department of Chemical Engineering, University of Delaware, Newark, Delaware 19716, USA
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110
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Siani A, Captain B, Alexeev OS, Stafyla E, Hungria AB, Midgley PA, Thomas JM, Adams RD, Amiridis MD. Improved CO oxidation activity in the presence and absence of hydrogen over cluster-derived PtFe/SiO2 catalysts. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:5160-7. [PMID: 16700608 DOI: 10.1021/la053476a] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The catalytic performance of cluster-derived PtFe/SiO(2) bimetallic catalysts for the oxidation of CO has been examined in the absence and presence of H(2) (PROX) and compared to that of Pt/SiO(2). PtFe(2)/SiO(2) and Pt(5)Fe(2)/SiO(2) samples were prepared from PtFe(2)(COD)(CO)(8) and Pt(5)Fe(2)(COD)(2)(CO)(12) organometallic cluster precursors, respectively. FTIR data indicate that both clusters can be deposited intact on the SiO(2) support. The clusters remained weakly bonded to the SiO(2) surface and could be extracted with CH(2)Cl(2) without any significant changes in their structure. Subsequent heating in H(2) led to complete decarbonylation of the supported clusters at approximately 350 degrees C and the formation of Pt-Fe nanoparticles with sizes in the 1-2 nm range, as indicated by HRTEM imaging. A few larger nanoparticles enriched in Pt were also observed, indicating that a small fraction of the deposited clusters were segregated to the individual components following the hydrogen treatment. A higher degree of metal dispersion and more homogeneous mixing of the two metals were observed during HRTEM/XEDS analysis with the cluster-derived samples, as compared to a PtFe/SiO(2) catalyst prepared through a conventional impregnation route. Furthermore, the cluster-derived PtFe(2)/SiO(2) and Pt(5)Fe(2)/SiO(2) samples were more active than Pt/SiO(2) and the conventionally prepared PtFe/SiO(2) sample for the oxidation of CO in air. However, substantial deactivation was also observed, indicating that the properties of the Pt-Fe bimetallic sites in the cluster-derived samples were altered by exposure to the reactants. The Pt(5)Fe(2)/SiO(2) sample was also more active than Pt/SiO(2) for PROX with a selectivity of approximately 92% at 50 degrees C. In this case, the deactivation with time on stream was substantially slower, indicating that the highly reducing environment under the PROX conditions helps maintain the properties of the active Pt-Fe bimetallic sites.
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Affiliation(s)
- Attilio Siani
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA
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111
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Tian WQ, Ge M, Gu F, Yamada T, Aoki Y. Binary Clusters AuPt and Au6Pt: Structure and Reactivity within Density Functional Theory. J Phys Chem A 2006; 110:6285-93. [PMID: 16686464 DOI: 10.1021/jp055506o] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Within density functional theory with the general gradient approximation for the exchange and correlation, the bimetallic clusters AuPt and Au(6)Pt have been studied for their structure and reactivity. The bond strength of AuPt lies between those of Au(2) and Pt(2), and it is closer to that of Au(2). The Pt atom is the reactive center in both AuPt and AuPt(+) according to electronic structure analysis. AuPt(+) is more stable than AuPt. Au(6)Pt prefers electronic states with low multiplicity. The most stable conformation of Au(6)Pt is a singlet and has quasi-planar hexagonal frame with Pt lying at the hexagonal center. The doping of Pt in Au cluster enhances the chemical regioselectivity of the Au cluster. The Pt atom essentially serves as electron donor and the Au atoms bonded to the Pt atom acts as electron acceptor in Au(6)Pt. The lowest triplet of edge-capped rhombus Au(6)Pt clusters is readily accessible with very small singlet-triplet energy gap (0.32 eV). O(2) prefers to adsorb on Au and CO prefers to adsorb on Pt. O(2) and CO have stronger adsorption on AuPt than they do on Au(6)Pt. CO has a much stronger adsorption on AuPt bimetallic cluster than O(2) does. The adsorption of CO on Pt modifies the geometry of AuPt bimetallic clusters.
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Affiliation(s)
- Wei Quan Tian
- State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China.
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112
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Hoover NN, Auten BJ, Chandler BD. Tuning Supported Catalyst Reactivity with Dendrimer-Templated Pt−Cu Nanoparticles. J Phys Chem B 2006; 110:8606-12. [PMID: 16640414 DOI: 10.1021/jp060833x] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of particle composition on heterogeneous catalysis were studied using dendrimer-encapsulated nanoparticles (DENs) as precursors to supported Pt-Cu catalysts. Bimetallic Pt-Cu DENs with varying Pt/Cu ratios were prepared in an anaerobic aqueous solution and deposited onto a high-purity commercial alumina support. The dendrimer template was then thermally removed to yield supported nanoparticle catalysts, which were studied with toluene hydrogenation and CO oxidation catalysis as well as infrared spectroscopy of adsorbed CO. Incorporating Cu into Pt nanoparticles had opposite effects on the two test reactions. Cu acted as a mild promoter for CO oxidation catalysis, and the promoting effect was independent of the amount of Cu present. Conversely, Cu acted as a strong poison for toluene hydrogenation catalysis, and the normalized rate tracked inversely with Cu content. Infrared spectroscopy of the supported nanoparticles indicated that electronic effects (electron donation from Cu to Pt) were minimal for these materials. Consequently, the catalysis results are interpreted in terms of potential structural differences as a function of Cu incorporation and reaction conditions.
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Affiliation(s)
- Natalie N Hoover
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, Texas 78212-7200, USA
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113
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Adams RD, Hollandsworth CB, Smith JL. Unsaturated Cyclopentadienyl-Molybdenum and Tungsten Carbonyl Cluster Complexes Containing Pd- and Pt(PBut3) Groups. Organometallics 2006. [DOI: 10.1021/om060107g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Richard D. Adams
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Carl B. Hollandsworth
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Jack L. Smith
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
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114
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115
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Belpassi L, Tarantelli F, Sgamellotti A, Quiney HM. The Electronic Structure of Alkali Aurides. A Four-Component Dirac−Kohn−Sham Study. J Phys Chem A 2006; 110:4543-54. [PMID: 16571062 DOI: 10.1021/jp054938w] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Spectroscopic constants, including dissociation energies, harmonic and anharmonic vibrational frequencies, and dipole moments, are calculated for the complete alkali auride series (LiAu, NaAu, KAu, RbAu, CsAu). The four-component formulation of relativistic density functional theory has been employed in this study, using the G-spinor basis sets implemented recently in the program BERTHA. The performance of four standard nonrelativistic density functionals employed is investigated by comparing the results with the best available theoretical and experimental data. The present work provides the first theoretical predictions on the molecular properties of RbAu. The intermetallic bond that occurs in the alkali auride series is highly polar and is characterized by a large charge transfer from the alkali metals to gold. The extent of this electron transfer has been investigated using several different charge analysis methods, enabling us to reach some general conclusions on their relative performance. We further report a detailed analysis of the topological properties of relativistic electron density in the bonding region, discussing the features of this approach which characterize the nature of the chemical bond. We have also computed the fully relativistic density for the alkali halides MBr and MI (M = Li, Na, K, Rb, and Cs). The comparative study shows that, on the basis of several topological properties and the variation in bond lengths, the gold atom behaves similarly to a halogen intermediate between Br and I.
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Affiliation(s)
- Leonardo Belpassi
- Dipartimento di Chimica e I.S.T.M.-C.N.R., Università di Perugia, 06123, Italy.
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116
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Ortiz-Soto LB, Alexeev OS, Amiridis MD. Low temperature oxidation of CO over cluster-derived platinum-gold catalysts. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:3112-7. [PMID: 16548565 DOI: 10.1021/la052358k] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The structural and catalytic properties of SiO2- and TiO2 -supported Pt-Au bimetallic catalysts prepared by coimpregnation were compared with those of samples of similar composition synthesized from a Pt2Au4(C{triple bond}CBut)8 cluster precursor. The smallest metal particles were formed when the bimetallic cluster was used as a precursor and TiO2 as the support. FTIR data indicate that highly dispersed Au crystallites in these samples, presumably located in close proximity to Pt, are capable of linearly coordinating CO molecules with a characteristic vibration observed at 2111 cm(-1). The cluster-derived Pt2Au4/TiO2 samples were the only ones exhibiting low-temperature CO oxidation activity, indicating that both the high dispersion of Au and the nature of the support are important factors affecting the catalytic activity for this system.
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Affiliation(s)
- Lorna B Ortiz-Soto
- Department of Chemical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA
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117
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Cavigliasso G, Lovell T, Stranger R. Periodic trends in metal–metal interactions in face-shared [M2Cl9]z−systems. Dalton Trans 2006:2017-25. [PMID: 16609773 DOI: 10.1039/b512393c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The periodic trends in metal-metal interactions in even-electron and mixed-valence [M2Cl9]z- face-shared systems, involving transition metals in Groups 4 to 8 and electronic configurations ranging from d1d1 through to d5d5 and from d1d2 through to d4d5, have been investigated by calculating metal-metal bonding and spin polarization (exchange) effects using density functional theory. These two terms are in opposition to one another and their relative difference determines the extent to which the metal-based electrons are delocalized and thus the degree of metal-metal bonding. Remarkably strong linear correlations between the two terms, and between each term and the square of the spin density on the metal centres, have been obtained for all group and period series considered, and are discussed in terms of their dependence on the metal orbital properties and electron density.
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Affiliation(s)
- Germán Cavigliasso
- Department of Chemistry, Faculty of Science, Australian National University, Canberra, ACT 0200, Australia
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118
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Adams RD, Captain B, Zhu L. Addition of Alkynes to High Nuclearity Platinum–Ruthenium Carbonyl Cluster Complexes. J CLUST SCI 2005. [DOI: 10.1007/s10876-005-0006-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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119
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Adams RD, Captain B, Zhu L. Synthesis of PtRu5(CO)14(PBut3)(μ-H)2(μ6-C) and Its Reactions with Pt(PBut3)2, HGePh3, and HSnPh3. Inorg Chem 2005; 44:6623-31. [PMID: 16156619 DOI: 10.1021/ic051007q] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reaction of PtRu5(CO)15(PBut3)(C), 3, with hydrogen at 97 degrees C yielded the new dihydride-containing cluster compound PtRu5(CO)14(PBut3)(mu-H)2(mu6-C), 5. Compound 5 was characterized crystallographically and was shown to contain an octahedral cluster consisting of one platinum and five ruthenium atoms with a carbido ligand in the center. Two hydrido ligands bridge two oppositely positioned PtRu bonds. Compound 5 reacts with Pt(PBut3)2 to yield Pt2Ru5(CO)14(PBut3)2(mu-H)2(mu6-C), 6, a Pt(PBut3) adduct of 5, by adding a Pt(PBut3) group as a bridge across one of the Ru-Ru bonds in the square base of the Ru5 portion of the cluster. Compound 6 is dynamically active on the NMR time scale by a mechanism that appears to involve a shifting of the Pt(PBut3) group from one Ru-Ru bond to another. Two new complexes, PtRu5(CO)13(PBut3)(mu-H)3(GePh3)(mu5-C), 7, and PtRu5(CO)13(PBut3)(mu-H)2(mu-GePh2)(mu6-C), 8, were obtained from the reaction of 5 with HGePh3. The cluster of 7 has an open structure in which the Pt(PBut3) group bridges an edge of the square base of the square pyramidal Ru5 cluster. Compound 7 also has three bridging hydrido ligands and one terminal GePh3 ligand. When heated to 97 degrees C, 7 is slowly converted to 8 by cleavage of a phenyl group from the GePh3 ligand and elimination of benzene by its combination with one of the hydrido ligands. The PtRu5 metal cluster of 8 has a closed octahedral shape with a GePh2 ligand bridging one of the Ru-Ru bonds. Two tin-containing compounds, PtRu5(CO)13(PBut3)(mu-H)3(SnPh3)(mu5-C), 9, and PtRu5(CO)13(PBut3)(mu-H)2(mu-SnPh2)(mu6-C), 10, which are analogous to 7 and 8 were obtained from the reaction of 5 with HSnPh3.
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Affiliation(s)
- Richard D Adams
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA.
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120
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Adams RD, Captain B, Zhu L. New High Nuclearity Platinum−Ruthenium Carbonyl Cluster Complexes Containing a Phenylacetylene Ligand: Structures and Properties. Organometallics 2005. [DOI: 10.1021/om050175n] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Richard D. Adams
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Burjor Captain
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
| | - Lei Zhu
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208
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121
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Scott RWJ, Sivadinarayana C, Wilson OM, Yan Z, Goodman DW, Crooks RM. Titania-Supported PdAu Bimetallic Catalysts Prepared from Dendrimer-Encapsulated Nanoparticle Precursors. J Am Chem Soc 2005; 127:1380-1. [PMID: 15686363 DOI: 10.1021/ja044446h] [Citation(s) in RCA: 177] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the synthesis, characterization, and catalytic activity of titania-supported bimetallic PdAu particles prepared using dendrimer-encapsulated nanoparticle (DEN) precursors. Single-particle energy-dispersive spectroscopy indicates a homogeneous distribution of bimetallic nanoparticles having compositions closely related to the metal-ion ratios used to prepare the DEN precursors. The catalytic activity of the supported PdAu catalysts was compared to that of supported Pd-only and Au-only catalysts; the enhanced CO oxidation activity of the PdAu catalysts is indicative of a synergetic bimetallic interaction.
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Affiliation(s)
- Robert W J Scott
- Department of Chemistry, Texas A and M University, P. O. Box 30012, College Station, TX 77842-3012, USA
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122
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Behrens S, Spittel G. A new palladium nanoparticle catalyst on mesoporous silica prepared from a molecular cluster precursor. Dalton Trans 2005:868-73. [PMID: 15726138 DOI: 10.1039/b415665j] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A promising approach to the controlled synthesis of supported nanoparticles involves the use of molecular carbonyl clusters as precursors. Molecular metal clusters consist of a defined number of structurally ordered atoms, and active monodisperse metal particles are formed after dispersing the molecules and removing the ligands. An octanuclear palladium cluster precursor with easily displaceable ligands was used to generate palladium nanoparticles on mesoporous MCM-41. The molecular cluster precursor, [Pd8(CO)8(PMe3)7], was directly adsorbed from solution onto MCM-41, followed by gentle thermolysis which yielded small metal nanoparticles. Compared to MCM-41-based catalysts prepared from palladium salts by conventional methods, this cluster-derived palladium catalyst has shown an efficient activity for liquid-phase hydrogenation of alkenes.
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Affiliation(s)
- Silke Behrens
- Institute for Technical Chemistry, Forschungszentrum Karlsruhe, Postfach 3640, 76021 Karlsruhe, Germany.
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123
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Lang H, Maldonado S, Stevenson KJ, Chandler BD. Synthesis and Characterization of Dendrimer Templated Supported Bimetallic Pt−Au Nanoparticles. J Am Chem Soc 2004; 126:12949-56. [PMID: 15469292 DOI: 10.1021/ja046542o] [Citation(s) in RCA: 256] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Bimetallic dendrimer-stabilized nanoparticles (DSNs) were used to prepare supported Pt-Au catalysts within the bulk miscibility gap for this binary system. Hydroxy-terminated generation 5 PAMAM dendrimers were used to prepare Cu(0) nanoparticles (NPs). The Cu(0) NPs were subsequently used to reduce K(2)PtCl(4) and HAuCl(4), preparing stabilized bimetallic Pt-Au NPs with a 1:1 stoichiometry. The stabilized NPs were adsorbed onto a high surface area silica support and thermally activated to remove the dendrimers. Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and infrared spectroscopy of adsorbed CO showed that this preparation route resulted in NPs in which the two metals are intimately mixed and that the majority of the bimetallic NPs were smaller than 3 nm. Further, the bimetallic NPs were highly active for CO oxidation catalysis near room temperature and showed evidence of CO induced restructuring at ambient temperatures.
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Affiliation(s)
- Huifang Lang
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, TX 78212-7200, USA
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124
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Adams RD, Captain B, Fu W, Smith JL, Smith MD. Addition of Platinum and Palladium Tri-tert-butyl Phosphine Groups to Open Pt−Fe and Pt−Ru Metal Carbonyl Clusters. Organometallics 2004. [DOI: 10.1021/om0342659] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Richard D. Adams
- Department of Chemistry and Biochemistry and the USC Nanocenter, University of South Carolina, Columbia, South Carolina 29208
| | - Burjor Captain
- Department of Chemistry and Biochemistry and the USC Nanocenter, University of South Carolina, Columbia, South Carolina 29208
| | - Wei Fu
- Department of Chemistry and Biochemistry and the USC Nanocenter, University of South Carolina, Columbia, South Carolina 29208
| | - Jack L. Smith
- Department of Chemistry and Biochemistry and the USC Nanocenter, University of South Carolina, Columbia, South Carolina 29208
| | - Mark D. Smith
- Department of Chemistry and Biochemistry and the USC Nanocenter, University of South Carolina, Columbia, South Carolina 29208
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125
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A review of in situ XAS study on Co-based bimetallic catalysts relevant to CO hydrogenation. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s0167-2991(04)80075-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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126
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Balducci G, Ciccioli A, Gigli G. A mass spectrometric and density functional study of the intermetallic molecules AuBe, AuMg, and AuCa. J Chem Phys 2004; 121:7748-55. [PMID: 15485236 DOI: 10.1063/1.1793971] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The intermetallic molecules AuBe and AuCa were identified by means of the Knudsen-Effusion Mass Spectrometry technique in the high-temperature vapors produced by vaporizing Au-Be-Ca alloys of proper composition. The gaseous equilibria AuBe(g)+Au(g)=Au(2)(g)+Be(g) and AuCa(g)+Au(g)=Au(2)(g)+Ca(g) were studied in the temperature ranges 1720-1841 K and 1669-1841 K, respectively, by monitoring the partial pressures of all the species involved. The equilibrium data were analyzed by the third-law method, obtaining for the first time the dissociation energy D(0) ( composite function) of the two intermetallic species: D(0) ( composite function)(AuBe)=234.0+/-4.0 kJ/mol; D(0) ( composite function)(AuCa)=246.7+/-4.0 kJ/mol. These values are significantly higher than the recently published D(0) ( composite function) of the species AuMg (175.4+/-2.7 kJ/mol). Furthermore, the ionization energies (IE) of AuBe, AuMg, and AuCa were obtained by measuring the electron impact ionization efficiency curves, IE(AuBe)=7.5+/-0.3 eV, IE(AuMg)=6.7+/-0.3 eV, and IE(AuCa)=5.5+/-0.3 eV. Theoretical calculations were also carried out for these species by density functional theory methods (PW91 and BP86) used in conjunction with Stuttgart relativistic effective core potentials. Both functionals were found to perform very well in reproducing experimental D(0) ( composite function), IE, and molecular parameters.
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Affiliation(s)
- G Balducci
- Dipartimento di Chimica, Università degli Studi di Roma La Sapienza, piazzale A. Moro 5, I-00185 Rome, Italy
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