Baixe Research Advances in Platinum Metals and Their Alloys: A Review of Recent Literature e outras Resumos em PDF para Química Aplicada, somente na Docsity!
PROPERTIES
Study of an Internally-Oxidized Pd0.97Ce0.03 Alloy V. M. AZAMBUJA, D. S. DOS SANTOS, L. PONTONNIER, M. MORALES and D. FRUCHART, Scr. Mater. , 2006, 54 , (10), 1779– Cold-worked foils of Pd0.97Ce0.03 underwent an inter- nal oxidisation heat treatment at 1073 K for 72 h. TEM showed the precipitation of needle-shaped CeO 2 (1) with a cubic lattice parameter of 5.4 Å. (1) exhibited preferential growth directions relative to the Pd matrix which correspond to the diagonal of the Pd cube. (1) were ~ 20–40 nm wide and 1–2 !m long, in coherence with the Pd matrix.
X-ray Photoelectron Spectroscopy and Magnetism
of Mn–Pd Alloys M. COLDEA, M. NEUMANN, S. G. CHIUZBAIAN, V. POP, L. G. PASCUT, O. ISNARD, A. F. TAKÁCS and R. PACURARIU, J. Alloys Compd. , 2006, 417 , (1–2), 7– Mn x Pd1– x alloys and compounds (1) were prepared by Ar arc melting. The samples were melted repeat- edly (four times) in the same atmosphere to ensure homogeneity. The electronic structures of (1) were studied using XPS. Both valence band and core level spectra were analysed. The magnetic properties of (1) are strongly correlated with their crystallographic properties and can be explained considering only the near-neighbour antiferromagnetic interactions between both Mn and Pd atoms and Mn–Mn pairs.
Dramatic Evolution of Magnetic Properties
Induced by Electronic Change in Ce(Pd1– xAg x) 2 Al 3 P. SUN, Q. LU, T. IKENO, T. KUWAI, T. MIZUSHIMA and Y. ISIKAWA, J. Phys.: Condens. Matter , 2006, 18 , (24), 5715– Measurements of lattice parameters ( a , c ), magnetic susceptibility "( T ) and magnetisation M ( H ), specific heat C ( T ), and electrical resistivity #( T ) were made for Ce(Pd1– x Ag x ) 2 Al 3. It was found that with increasing x the system varies from antiferromagnetism to ferro- magnetism at x ~ 0.05, then back at x ~ 0.45. The magnetic evolution resembles that of Ce(Pd1– x Cu x ) 2 Al 3.
CHEMICAL COMPOUNDS
Protonation of Platinum(II) Dialkyl Complexes
Containing Ligands with Proximate H-Bonding
Substituents G. J. P. BRITOVSEK, R. A. TAYLOR, G. J. SUNLEY, D. J. LAW and A. J. P. WHITE, Organometallics , 2006, 25 , (8), 2074– Pt(II) dimethyl complexes [Pt(L)Me 2 ], L = unsym- metrically substituted bipyridine, were prepared. Reactions in MeCN with 1 equiv. of a strong acid gave [Pt(L)Me(CH 3 CN)]+. The selectivity of the pro- tonation reactions is reported to be governed by steric effects rather than H-bonding effects.
Synthesis and Structure of NbPdSi M. VALLDOR and R. PÖTTGEN, Z. Naturforsch. , 2006, 61b , (3), 339– NbPdSi (1) was prepared by melting the elements in an arc furnace. Well-shaped single crystals of (1) were obtained by annealing in an induction furnace. The Pd and Si atoms were shown by powder and single crystal XRD analysis to build up a 3D [PdSi] network where each Pd atom has a strongly distorted tetrahe- dral Si coordination at Pd–Si of 242–250 pm. The Nb atoms fill channels left in the [PdSi] network.
N-Heterocyclic Carbenes: Synthesis, Structures, and Electronic Ligand Properties W. A. HERRMANN, J. SCHÜTZ, G. D. FREY and E. HERDTWECK, Organometallics , 2006, 25 , (10), 2437– Rh(COD)X(NHC) complexes were synthesised. The relative $-donor/%-acceptor quality of various NHC ligands was classified by means of IR spec- troscopy at the corresponding Rh(CO) 2 I(NHC). Single crystal XRD studies of Rh pyrazolin- and tetra- zolinylidene complexes are reported. Different azolium salts were applied to obtain Rh and Ir com- plexes with two and four carbene ligands.
Bis[iridium(I)] Complex of Inverted N-Confused Porphyrin M. TOGANOH, J. KONAGAWA and H. FURUTA, Inorg. Chem. , 2006, 45 , (10), 3852– When a N-confused tetraphenylporphyrin was treated with 2.0 equiv. of IrCl(CO) 2 ( p -toluidine) and 10 equiv. of NaOAc in toluene/THF = 20/1 (v/v) at 100ºC for 3.5 h, a novel bis[iridium(I)] complex (1), wherein the confused pyrrole ring took an inverted conformation, was obtained in 17% yield. The reac- tions were significantly accelerated by THF. (1) can be handled in air without special care. No decompo- sition was observed by heating in 1,2-Cl 2 C 6 H 4. No demetallation occurred on CF 3 COOH addition.
Fullerene Polypyridine Ligands: Synthesis, Ruthenium Complexes, and Electrochemical and Photophysical Properties Z. ZHOU, G. H. SAROVA, S. ZHANG, Z. OU, F. T. TAT, K. M. KADISH, L. ECHEGOYEN, D. M. GULDI, D. I. SCHUSTER and S. R. WILSON, Chem. Eur. J. , 2006, 12 , (16), 4241– Fullerene coordination ligands (1) with a single bpy or tpy unit were synthesised. Coordination of (1) to Ru(II) gave linear rod-like donor-acceptor systems. Steady-state fluorescence of [Ru(bpy) 2 (bpy-C 60 )]2+ showed a rapid solvent-dependent, intramolecular quenching of the Ru(II) MLCT excited state. Electrochemical studies on [Ru(bpy) 2 (bpy-C 60 )]2+^ and [Ru(tpy)(tpy-C 60 )]2+^ indicated electronic coupling between the Ru centre and the fullerene core.
Platinum Metals Rev. , 2006, 50 , (3), 150–153 150
ABSTRACTS
of current literature on the platinum metals and their alloys
DOI: 10.1595/147106706X
ELECTROCHEMISTRY
Chemical and Electrochemical Synthesis of
Polyaniline/Platinum Composites J. M. KINYANJUI, N. R. WIJERATNE, J. HANKS and D. W. HATCHETT, Electrochim. Acta , 2006, 51 , (14), 2825– The direct chemical synthesis of Pt-polyaniline (1) composites was achieved by the oxidation of aniline by PtCl 6 2–. The Pt particles were ~ 1 !m in diameter. Electrochemical synthesis of (1) was initiated by the uptake and reduction of PtCl 6 2–^ into an a priori elec- trochemically deposited polyaniline film. This method produced a uniform dispersion of Pt particles with diameters of 200 nm–1 !m.
Electrocatalytic Activity for Hydrogen Evolution of
Polypyrrole Films Modified with Noble Metal
Particles M. TRUEBA, S. P. TRASATTI and S. TRASATTI, Mater. Chem. Phys. , 2006, 98 , (1), 165– Polypyrrole (Ppy) films with Pt, Ru and Ir particles were electrosynthesised on the surface of austenitic stainless steel by: (a) electrodeposition of a polymer film from a solution already containing an anionic metal complex, followed by potentiodynamic or gal- vanostatic reduction; or (b) presynthesised Ppy films modified by galvanostatic electrodeposition of the metals from solutions of their metal complexes. The electrocatalytic activity of the modified electrodes for the H 2 evolution reaction was tested in H 2 SO 4 (0. M) by potentiodynamic techniques (0.5 mV s–1).
PHOTOCONVERSION
Platinum–Acetylide Polymer Based Solar Cells:
Involvement of the Triplet State for Energy
Conversion F. GUO, Y.-G. KIM, J. R. REYNOLDS and K. S. SCHANZE, Chem. Commun. , 2006, (17), 1887– Blends of a blue-violet absorbing Pt-acetylide polymer (1) with 1-(3-(methoxycarbonyl)propyl)-1- phenyl[6.6]C 61 (PCBM), can be used as the active material in a photovoltaic device. (1) acts as the chro- mophore and electron donor blended with PCBM as an electron acceptor. Photoinduced charge separation in the blends is believed to occur via the triplet excit- ed state of the organometallic polymer.
Structurally Integrated Organic Light Emitting
Device-Based Sensors for Gas Phase and
Dissolved Oxygen R. SHINAR, Z. ZHOU, B. CHOUDHURY and J. SHINA, Anal. Chim. Acta , 2006, 568 , (1–2), 190– The O 2 -sensitive dyes Pt- or Pd-octaethylporphyrin (1), were embedded in polystyrene, or dissolved in solution. Their performance was compared to that of Ru(dpp) 3 2+. A green OLED, based on Alq 3 , was used to excite (1). The O 2 level was monitored in the gas phase and in H 2 O, EtOH and toluene by measuring changes in the PL lifetime & of (1).
Photophysical Properties of the Photosensitizer [Ru(bpy) 2 (5-CNphen)]2+^ and Intramolecular Quenching by Complexation of Cu(II) M. G. MELLACE, F. FAGALDE, N. E. KATZ, H. R. HESTER and R. SCHMEHL, J. Photochem. Photobiol. A: Chem. , 2006, 181 , (1), 28– The lifetime of the 3 MLCT emitting state of [Ru(bpy) 2 (5-CNphen)]2+^ has been determined in MeCN by flash photolysis and time correlated single photon counting techniques. The value obtained, & = 2.2 !s, suggests its potential use as a photosensitiser in molecular devices. Static and dynamic quenching of the complex luminescence by Cu2+^ ions was seen.
ELECTRODEPOSITION AND SURFACE
COATINGS
Adhesion and Bonding of Pt/Ni and Pt/Co Overlayers: Density Functional Calculations G. F. CABEZA, N. J. CASTELLANI and P. LÉGARÉ, J. Phys. Chem. Solids , 2006, 67 , (4), 690– The electronic and energetic properties of Pt/Ni and Pt/Co surfaces are examined using the full- potential linearised augmented plane wave method. The results of the shifts in the d-band centers when one metal (Pt) is pseudomorfically deposited on another with smaller lattice constant (Ni, Co) are pre- sented, together with those corresponding to the surface and adhesion energies. The results for pure Ni, Co and Pt surfaces are given to compare with data in the literature.
Self-Assembled Palladium Nanowires by Electroless Deposition Z. SHI, S. WU and J. A. SZPUNAR, Nanotechnology , 2006, 17 , (9), 2161– The self-assembly production of Pd nanowires (1) has been carried out by electroless deposition on a porous stainless steel template. Various arrays of self- assembled (1) in the form of single wire, parallel and curved wires, intersections and network structures are obtainable. (1) can be built in a self-assembled man- ner by the assembly of nanoparticles generated in the initial stages of the deposition without any external field except the chemical reaction.
Selective Growth of IrO 2 Nanorods Using Metalorganic Chemical Vapor Deposition G. WANG, D.-S. TSAI, Y.-S. HUANG, A. KOROTCOV, W.-C. YEH and D. SUSANTI, J. Mater. Chem. , 2006, 16 , (8), 780– Area-selective growth of IrO 2 nanorods (1) was achieved via MOCVD using (MeCp)Ir(COD) on a sapphire (012) or (100) substrate which consisted of patterned SiO 2 as the nongrowth surface. Orientation of (1) was controlled by the in-plane epitaxial relation between the IrO 2 crystal and sapphire, along with the IrO 2 growth habit in the [001] direction. The pho- tolithography method gave better resolution in preserving rod orientation of (1) at the growth and nongrowth boundary zone.
HOMOGENEOUS CATALYSIS
Recovery and Reuse of Ionic Liquids and
Palladium Catalyst for Suzuki Reactions Using
Organic Solvent Nanofiltration H. WONG, C. J. PINK, F. C. FERREIRA and A. G. LIVINGSTON, Green Chem. , 2006, 8 , (4), 373– Organic solvent nanofiltration was used for separat- ing ionic liquids (1) and the catalyst Pd 2 (dba) 3 -CHCl 3 from Suzuki cross-couplings. The reactions were car- ried out in 50:50 wt.% ethyl acetate and (1). The post reaction mixture was diluted further with ethyl acetate and then separated by nanofiltration. The product was recovered in the nanofiltration permeate, while (1) and Pd catalyst were retained by the membrane.
Unexpected Roles of Molecular Sieves in
Palladium-Catalyzed Aerobic Alcohol Oxidation B. A. STEINHOFF, A. E. KING and S. S. STAHL, J. Org. Chem. , 2006, 71 , (5), 1861– The effect of molecular sieves (MS3A) on Pd(OAc) 2 /pyridine (1) and Pd(OAc) 2 /DMSO (2) was investigated by performing kinetic studies of alcohol oxidation. MS3A enhanced the rate of (1)-catalysed oxidation of alcohols. This was attributed to the abil- ity of MS3A to serve as a Brønsted base. In contrast, no rate enhancement was observed with (2). Both (1) and (2) exhibit improved catalyst stability in the pres- ence of MS3A, resulting in higher catalytic TONs. The MS3A provided a heterogeneous surface that hinders bulk aggregation of Pd metal.
Unsymmetric-1,3-Disubstituted Imidazolium Salt
for Palladium-Catalyzed Suzuki-Miyaura Cross-
Coupling Reactions of Aryl Bromides H.-W. YU, J.-C. SHI, H. ZHANG, P.-Y. YANG, X.-P. WANG and Z.- L. JIN, J. Mol. Catal. A: Chem. , 2006, 250 , (1–2), 15– Unsymmetric 1,3-disubstituted-imidazolium salts (1) derived from ferrocene were prepared, and their preliminary activities as precursors of N-heterocyclic carbene ligands for Pd-catalysed cross-coupling of aryl bromides with phenylboronic acid were studied. A combination of Pd(OAc) 2 and (1) was an excellent catalyst system for the Suzuki-Miyaura cross-coupling of aryl bromides with phenylboronic acid in the pres- ence of Cs 2 CO 3.
Rh(0) Nanoparticles as Catalyst Precursors for the
Solventless Hydroformylation of Olefins A. J. BRUSS, M. A. GELESKY, G. MACHADO and J. DUPONT, J. Mol. Catal. A: Chem. , 2006, 252 , (1–2), 212– The hydroformylation of 1-alkenes can be performed in solventless conditions, using ligand-modified or unmodified Rh(0) nanoparticles (1) prepared in imi- dazolium ionic liquids as catalyst precursors. Aldehydes were generated when 5.0 nm (1) are used. With smaller nanoparticles, chemoselectivity is decreased; large sized nanoparticles (15 nm) produce only small amounts of aldehydes, similarly to a classi- cal heterogeneous Rh/C catalyst precursor.
FUEL CELLS
Thermal Stability in Air of Pt/C Catalysts and PEM Fuel Cell Catalyst Layers O. A. BATURINA, S. R. AUBUCHON and K. J. WYNNE, Chem. Mater. , 2006, 18 , (6), 1498– The thermal stability of Pt/Vulcan XC 72 and a 46 wt.% Pt/Vulcan XC 72/Nafion layer was studied. Low temperature (100–200ºC) C combustion occured in the presence of Pt. In PEMFC catalyst layers, the thermal decomposition temperature of Nafion is low- ered by ~ 100ºC to 300ºC in the presence of Pt/C.
High Performance PtRuIr Catalysts Supported on Carbon Nanotubes for the Anodic Oxidation of Methanol S. LIAO, K.-A. HOLMES, H. TSAPRAILIS and V. I. BIRSS, J. Am. Chem. Soc. , 2006, 128 , (11), 3504– PtRuIr/C MWNTs system (1) was prepared using an organic colloid synthesis method. (1) has a very high real surface area and is highly active toward the oxidation of MeOH. The Ir component acts as a pro- moter. The splitting of the Pt(111) XRD feature into four peaks and the shift to larger d spacing reflect the high dispersion of the metallic components.
ELECTRICAL AND ELECTRONIC
ENGINEERING
Interface Effect on Ferroelectricity at the Nanoscale C.-G. DUAN, R. F. SABIRIANOV, W.-N. MEI, S. S. JASWAL and E. Y. TSYMBAL, Nano Lett. , 2006, 6 , (3), 483– A first-principles study of ultrathin KNbO 3 ferro- electric films (1) placed between two metal electrodes, either Pt or SrRuO 3 , was carried out. The strength of bonding and intrinsic dipole moments at the inter- faces was shown to control the ferroelectricity. The polarisation profile was inhomogeneous across the film thickness. The critical thickness for the net polar- isation of (1) was predicted to be ~ 1 nm for Pt and 1.8 nm for SrRuO 3 electrodes.
Calculations and Measurements of Contact Resistance of Semi-Transparent Ni/Pd Contacts to p-GaN K. H. A. BOGART and J. CROFTON, J. Electron. Mater. , 2006, 35 , (4), 605– Calculations of specific contact resistance (1) as a function of doping and barrier height were performed for p-GaN. (1) were measured for oxidised Ni/Au, Pd, and oxidised Ni/Pd ohmic contact metal schemes to p-GaN. The Ni/Pd contact had the lowest (1). Some Ni had diffused away from the GaN surface to the contact surface, with the bulk of the Pd located in between two areas of Ni. Both Ni and Pd interdif- fused with the GaN at the semiconductor surface. The majority of the O was as NiO. Predominantly NiO and PdO species were formed, with higher Ni and Pd oxides at the contact surface.
