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Journal Archive

Platinum Metals Rev., 2005, 49, (2), 102


ABSTRACTS: April 2005

of current literature on the platinum metals and their alloys



Dimeric Palladium Complexes with Bridging Aryl Groups: When Are They Stable?

A. C. ALBÉNIZ, P. ESPINET, O. LÓPEZ-CIMAS and B. MARTÍN-RUIZ, Chem. Eur. J., 2005, 11, (1), 242–252

LINK doi:10.1002/chem.200400612

[Pd2(μ-R)23-allyl)2] (R = haloaryl, mesityl) were prepared. The haloaryl complexes exchange between their cis and trans isomers (relative to the orientation of the two allyl groups in the dimer) by solvent-assisted associative bridge splitting. Stable aryl bridges are favoured by ancillary ligands of small size and lacking electron lone pairs, and aryl ligands reluctant to be involved in homo and hetero C–C coupling.

Synthesis, Structure and Electrochemical Properties of Tris-picolinate Complexes of Rhodium and Iridium

S. BASU, S.-M. PENG, G.-H. LEE and S. BHATTACHARYA, Polyhedron, 2005, 24, (1), 157–163

LINK doi:10.1016/j.poly.2004.10.015

The pic ligands of [M(pic)3] (1) (M = Rh, Ir; Hpic = picolinic acid) are coordinated as bidentate N,O-donors. A water of crystallisation molecule is H bonded to the carboxylate fragments of two adjacent (1) and acts a bridge between the individual (1). (1) are diamagnetic and show intense MLCT transitions in the visible region. CV on (1) shows a M(III)–M(IV) oxidation and a ligand-centred reductive response.

Iridium(I) and Rhodium(I) Cationic Complexes with Triphosphinocalix[6]arene Ligands: Dynamic Motion with Size-Selective Molecular Encapsulation

Y. OBORA, Y. K. LIU, L. H. JIANG, K. TAKENAKA, M. TOKUNAGA and Y. TSUJI, Organometallics, 2005, 24, (1), 4–6

LINK doi:10.1021/om049227j

The title complexes (1) exhibited dynamic behaviour with size-selective molecular encapsulation. Variable-temperature 31P{1H} NMR measurements were carried out in the presence of various molecules (1). (1) were divided into three groups, depending on the maximum projection area of the solvent-accessible surface, A: < 45 Å2, 45–68 Å2, and > 68 Å2. Molecules with A of 45–68 Å2 just fit in the cavity and slow the dynamic behaviour.

Synthesis and Derivatization of Iridium(I) and Iridium(III) Pentamethyl[60]fullerene Complexes

Y. MATSUO, A. IWASHITA and E. NAKAMURA, Organometallics, 2005, 24, (1), 89–95

LINK doi:10.1021/om049333l

Ir(η5-C60Me5)(CO)2 (1) was obtained from the reaction of K(C60Me5) with [IrCl(CO)2]2 in MeCN/THF. Oxidation of the Ir atom of (1) by I2 gave an Ir(III) complex, Ir(η5-C60Me5)I2(CO) (2). The iodo and carbonyl ligands of (2) can be readily replaced by alkyl, alkynyl, phosphine, and isonitrile ligands. (2) may be used as catalysts for organic synthesis.


Electrochemical Investigations of Platinum Phenylethynyl Complexes

L. KONDRACHOVA, K. E. PARIS, P. C. SANCHEZ, A. M. VEGA, R. PYATI and C. D. RITHNER, J. Electroanal. Chem., 2005, 576, (2), 287–294

LINK doi:10.1016/j.jelechem.2004.11.003

Pt phenylethynyl complexes exhibited irreversible oxidations in benzene/MeCN near +1.2 V vs. Ag|AgCl. However, trans-bis(tri-n-butylphosphine) bis(phenylethynyl)platinum(II) underwent reduction in THF at –2.786 V. Photophysical measurements established that as the phenylethynyl chain length increases, the absorbance wavelength increases. The emission wavelength shows a weak but similar trend.

Controlled Growth of a Single Palladium Nanowire between Microfabricated Electrodes

M. A. BANGAR, K. RAMANATHAN, M. YUN, C. LEE, C. HANGARTER and N. V. MYUNG, Chem. Mater., 2004, 16, (24), 4955–4959

LINK doi:10.1021/cm048931n

Dimensionally controlled growth of a single Pd nanowire (1) between premicrofabricated Au electrodes was achieved using an electrochemical method. (1) of 100 nm, 500 nm, and 1 μm wide and 2.5 μm long channels (length-to-diameter ratio ~ 2.5–25) were grown. Current of –100 nA was used.


A Luminescent Pt(II) Complex with a Terpyridine-Like Ligand Involving a Six-Membered Chelate Ring

Y.-Z. HU, M. H. WILSON, R. ZONG, C. BONNEFOUS, D. R. McMILLIN and R. P. THUMMEL, Dalton Trans., 2005, (2), 354–358

LINK doi:10.1039/b415021j

[Pt(1)Cl]+ (2) ((1) = 2-(8'-quinolinyl)-1,10-phenanthroline) was prepared. The six-membered chelate ring in (2) gives relief to the angle strain as well as some non-planarity in bound (1). In CH2Cl2 (2) exhibited higher energy charge-transfer absorption, but slightly lower energy emission than [Pt(3)Cl]+ ((3) = 2-(2'-pyridyl)-1,10-phenanthroline).

Electrochemical and Luminescent Properties of New Mononuclear Ruthenium(II) and Binuclear Iridium(III)-Ruthenium(II) Terpyridine Complexes

N. YOSHIKAWA, T. MATSUMURA-INOUE, N. KANEHISA, Y. KAI, H. TAKASHIMA and K. TSUKAHARA, Anal. Sci., 2004, 20, (12), 1639–1644

LINK doi:10.2116/analsci.20.1639

The title complexes include [RuII2Cl2(dpp)(terpy)2]2+ (1) and [IrIIIRuIICl2(dpp)(terpy)2]3+ (2) (dpp = 2,3-bis(2-pyridyl)pyrazine). The absorption spectra of (1) and (2) exhibit ligand-centred bands in the UV region and MLCT bands in the visible region. The HOMO is based on Ru, and the LUMO is dpp-based.

Design of Novel Efficient Sensitizing Dye for Nanocrystalline TiO2 Solar Cell; Tripyridine-thiolato (4,4',4''-tricarboxy-2,2':6',2''-terpyridine) ruthenium(II)

F. AIGA and T. TADA, Sol. Energy Mater. Sol. Cells, 2005, 85, (3), 437–446

LINK doi:10.1016/j.solmat.2004.04.020

The title Ru complex (1) was designed based on the DFT MO calculations with PBE0 functional. (1) is a modification of the Ru black dye (2), with the NCS ligands of (2) being replaced by C5H4NS ligands. (1) has a higher electron transfer rate from redox systems to oxidised dyes and higher absorption efficiency to the solar spectrum.

A Highly Efficient Redox Chromophore for Simultaneous Application in a Photoelectrochemical Dye Sensitized Solar Cell and Electrochromic Devices

A. F. NOGUEIRA, S. H. TOMA, M. VIDOTTI, A. L. B. FORMIGA, S. I. CÓRDOBA DE TORRESI and H. E. TOMA, New J. Chem., 2005, 29, (2), 320–324

LINK doi:10.1039/b411122b

Na6[{RuII(dicarboxybipyridine)2Cl}2(BPEB)] (1) (BPEB = trans-1,4-bis[2-(4-pyridyl)ethenyl]benzene) exhibits an electrochromic effect when reduced. The carboxylate groups of the bipyridine allow strong attachment to the surface of TiO2. This contributes to an efficient and reversible electron transfer from the oxide to the chromophoric ligand, colouring the oxide film blue. (1) also has a high photon-to-electron conversion efficiency when applied as a photoanode in a dye sensitised solar cell.


Characterizations of Pd–Ag Membrane Prepared by Sequential Electroless Deposition

W.-H. LIN and H.-F. CHANG, Surf. Coat. Technol., 2005, 194, (1), 157–166

LINK doi:10.1016/j.surfcoat.2004.07.089

Sequential electroless plating on porous stainless steel was used to prepare Pd-Ag membranes. AFM established that lower skin layer roughness and lower deposition rate were related. EDS confirmed the Pd-Ag deposit over and inside of the porous substrate to be homogeneous.

Preparation of Palladium and Silver Alloy Membrane on a Porous α-Alumina Tube via a Simultaneous Electroless Plating

D. A. PACHECO TANAKA, M. A. LLOSA TANCO, S. NIWA, Y. WAKUI, F. MIZUKAMI, T. NAMBA and T. M. SUZUKI, J. Membrane Sci., 2005, 247, (1–2), 21–27

LINK doi:10.1016/j.memsci.2004.06.002

For the title process, seeding of Pd nanoparticles (1) on an α-Al2O3 tube allowed codeposition of Pd and Ag. (1) were distributed by dip-coating with Pd acetate or [Pd(acac)2] in organic solvents followed by reduction with alkaline hydrazine solution. After simultaneous deposition, alloying of Pd and Ag was carried out at 500ºC for 4 h in H2.

Morphological Evolution of the Self-Assembled IrO2 One-Dimensional Nanocrystals

R.-S. CHEN, H.-M. CHANG, Y.-S. HUANG, D.-S. TSAI and K.-C. CHIU, Nanotechnology, 2005, 16, (1), 93–97

LINK doi:10.1088/0957-4484/16/1/019

The morphological evolution of IrO2 1D nanocrystals (1) via MOCVD has been observed. (1) result from a decrease in the degree of interface instability. (1) occur from triangular/wedged nanorods via incomplete/scrolled nanotubes to square nanotubes and square nanorods. The polycrystalline films composed of continuous 3D grains belong to the most stable form as compared to the 1D nanocrystals.

Thermophysical Properties and Deposition of B2 Structure Based Al–Ni–Ru–M Alloys

I. VJUNITSKY, P. P. BANDYOPADHYAY, St. SIEGMANN, M. DVORAK, E. SCHÖNFELD, T. KAISER, W. STEURER and V. SHKLOVER, Surf. Coat. Technol., 2005, 192, (2–3), 131–138

LINK doi:10.1016/j.surfcoat.2004.09.028

The normal value range for the thermal conductivity of the title alloys is 10–20 W m–1 K–1 at room temperature, but can be reduced to ~ 3.5 W m–1 K–1 by modifying the alloy composition. A fused and subsequently pulverised Al-Ni-Ru alloy was deposited on a Ni-based superalloy (modified CMSX-4) using vacuum and atmospheric plasma spraying. The coatings had favourable coating–substrate adhesion. A segregated intermetallic phase was detected at the Al50Ni40Ru10/modified CMSX-4 interface.


Fabrication and Characterisation of Ultra-Thin Tungsten–Carbon (W/C) and Platinum–Carbon (Pt/C) Multilayers for X-Ray Mirrors

B. K. GAN, B. A. LATELLA and R. W. CHEARY, Appl. Surf. Sci., 2005, 239, (2), 237–245

LINK doi:10.1016/j.apsusc.2004.05.269

Ultra-thin Pt/C and W/C multilayer films (1) were fabricated using DC magnetron sputtering. The bilayer period and the total number of layers were varied to ascertain the X-ray reflectance response. XPS established that a distinct intermixing layer develops in (1). (1) are mechanically reliable and have excellent adhesion. Hardness and Young's modulus improved with increasing number of layers. (1) have potential as mirrors for high energy X-ray applications.

Morphological Study of Supported Thin Pd and Pd–25Ag Membranes upon Hydrogen Permeation

Y. ZHANG, M. KOMAKI and C. NISHIMURA, J. Membrane Sci., 2005, 246, (2), 173–180

LINK doi:10.1016/j.memsci.2004.09.002

H2 permeation of Pd and Pd-25Ag membranes supported by V-15Ni was investigated at 423–673 K. The Pd-25Ag membrane was more resistant to H-induced cracking and grain growth. H permeation of the Pd-25Ag/V-15Ni membrane (1) was carried out at 573 and 673 K for 200 h. At 573 K, small amounts of oxide formed on the Pd-Ag surface. Whisker and fissure-oxide morphologies were dominant on the exit and entrance side of (1), respectively, along with severe metallic interdiffusion, at 673 K.


Preparation and Characterisation of Pt Containing NbMCM-41 Mesoporous Molecular Sieves Addressed to Catalytic NO Reduction by Hydrocarbons

I. SOBCZAK, M. ZIOLEK and M. NOWACKA, Microporous Mesoporous Mater., 2005, 78, (2–3), 103–116

LINK doi:10.1016/j.micromeso.2004.10.001

The title catalysts were prepared via impregnation of NbMCM-41 with Pt(NH3)4(NO3)2 or H2PtCl6 (1 wt.% of Pt). Smaller size Pt clusters were obtained with H2PtCl6. A FTIR study with NO + O2 + C3H6 indicated that Pt/NbMCM-41 has potential for the SCR process. The NbO species enhance the oxidative activity in NO → NO2, whereas the Pt species is responsible for hydrocarbon activation. NbMCM-41 acts as storage for the nitrate/nitrite species.

Flame-Made Pd/La2O3/Al2O3 Nanoparticles: Thermal Stability and Catalytic Behavior in Methane Combustion

R. STROBEL, S. E. PRATSINIS and A. BAIKER, J. Mater. Chem., 2005, 15, (5), 605–610

LINK doi:10.1039/b413198c

Flame spray pyrolysis was used to prepare Pd nanoparticles (< 5 nm) supported on La-stabilised Al2O3 (1) with specific surface areas of 50–180 m2 g–1. (1) was tested for the catalytic combustion of CH4. (1) exhibited excellent thermal stability in terms of specific surface area up to 1200ºC and retarded γ- to α-Al2O3 transformation. (1) was tested as-prepared and after sintering at 1000ºC (Pd particles, 50–150 nm). All the materials exhibited similar catalytic performance after an initial conditioning cycle if the temperature was cycled several times (200–1000ºC).

Effect of the Promoter and Support on the Catalytic Activity of Pd–CeO2-Supported Catalysts for CH4 Combustion

G. PECCHI, P. REYES, R. ZAMORA, T. LÓPEZ and R. GÓMEZ, J. Chem. Technol. Biotechnol., 2005, 80, (3), 268–272

LINK: doi:10.1002/jctb.1120

Pd-CeO2-supported catalysts, prepared by the sol-gel technique, were used for the catalytic combustion of CH4. The addition of CeO2 to Al2O3 gave a highly dispersed catalyst when compared with their ZrO2 counterparts. However, the catalytic activity of the Pd-CeO2-ZrO2 series is higher, due to the Pd having a larger particle size.

The Oxidation of Water by Cerium(IV) Catalysed by Nanoparticulate RuO2 on Mesoporous Silica

N. C. KING, C. DICKINSON, W. ZHOU and D. W. BRUCE, Dalton Trans., 2005, (6), 1027–1032

LINK doi:10.1039/b415288c

Mesoporous silicates were prepared by templating on the hexagonal mesophase of bis(2,2'-bipyridine)(4,4'-dinonadecyl-2,2'-bipyridine)ruthenium(II) dichloride using liquid-crystal templating. On calcination, the surfactant template was removed, except for the central Ru ion that was oxidised to RuO2 nanoparticles (1) within the pores. (1) were active in catalysing the oxidation of H2O by acidic CeIV.


Pd Nanoparticle Aging and Its Implications in the Suzuki Cross-Coupling Reaction

J. HU and Y. LIU, Langmuir, 2005, 21, (6), 2121–2123

LINK doi:10.1021/la0471902

The Pd nanoparticles (1) recovered from the N,N-dihexylcarbodiimide–Pd nanoparticle composite catalysts used in Suzuki cross-couplings, were found to transform from spherical-shape to larger needle-shaped crystals. (1) aggregated into nanosized blackberry-like assemblies (100–200 nm) as a result of Ostwald ripening. In a second type of ripening, atomic rearrangement occurred and (1) transformed into needle-shaped nanocrystals. These observations will be important for the future design and optimisation of durable nanoparticle catalysts.

Pd(II)-Biquinoline Catalyzed Aerobic Oxidation of Alcohols in Water

B. P. BUFFIN, J. P. CLARKSON, N. L. BELITZ and A. KUNDU, J. Mol. Catal. A: Chem., 2005, 225, (1), 111–116

LINK doi:10.1016/j.molcata.2004.08.035

Pd(OAc)2 stabilised by 2,2'-biquinoline-4,4'-dicarboxylic acid was used in the aerobic oxidation of primary and secondary alcohols. H2O was used as the reaction solvent, with air as the oxidant. Aliphatic primary alcohols were fully oxidised to carboxylic acid products. Secondary alcohols gave the corresponding ketones. The catalyst can be recycled.

New Carbazole–Oxadiazole Dyads for Electroluminescent Devices: Influence of Acceptor Substituents on Luminescent and Thermal Properties

K. R. J. THOMAS, J. T. LIN, Y.-T. TAO and C.-H. CHUEN, Chem. Mater., 2004, 16, (25), 5437–5444

LINK doi:10.1021/cm048794u

Oxadiazole-incorporated carbazoylylamines (1) were synthesised using Pd catalysed C–N coupling reactions with Pd(dba)2/P(t-Bu)3 catalyst and t-BuONa base. The reactions were best carried out in toluene at 80ºC. Yields of (1) ranged from 75–95%. (1) were purified by reprecipitating twice from CH2Cl2/MeOH before application in the electroluminescent devices, such as OLEDs.

Hydroformylation of 1-Hexene in Ionic Liquids Catalyzed by Highly Active Rhodium-Phosphine Complexes

H. ZHENG, M. LI, H. CHEN, R. LI and X. LI, Chin. J. Catal., 2005, 26, (1), 4–6

The hydroformylation of 1-hexene catalysed by HRh(CO)(TPPTS)3 complexes (1) (TPPTS = triphenylphosphine-m-trisulfonic acid trisodium salt) was carried out in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF4). The activity and selectivity of (1) in [bmim]BF4 were higher than those in other ionic liquids. The TOF of 1-hexene and selectivity for aldehyde were 1508 h–1 and 92%, respectively, under optimum conditions. The high activity of (1) is due to its higher solubility in [bmim]BF4 and to the absence of halide ions.

Mononuclear Ruthenium Catalysts for the Direct Propargylation of Heterocycles with Propargyl Alcohols

E. BUSTELO and P. H. DIXNEUF, Adv. Synth. Catal., 2005, 347, (2–3), 393–397

LINK doi:10.1002/adsc.200404219

While [(p-cymene)RuCl(PR3)][OTf] (PR3) (PR3 = PCy3, PPh3) catalyse the propargylation of furan or 2-methylfuran by the alkynol HCºCCH(OH)Ph in moderate yield, [(p-cymene)RuCl(CO)(PR3)][OTf] are more active. The stoichiometric reaction of [(p-cymene)RuCl(PR3)][B(ArF)4] (ArF = 3,5-(CF3)2C6H3) and the alkynol resulted in the in situ formation, via allenylidene and hydroxycarbene intermediates, of [(p-cymene)RuCl(CO)(PR3)]B(ArF)4].

An Efficient Catalytic Asymmetric Route to 1-Aryl-2-imidazol-1-yl-ethanols

I. C. LENNON and J. A. RAMSDEN, Org. Process Res. Dev., 2005, 9, (1), 110–112

LINK doi:10.1021/op049838n

Catalytic asymmetric transfer hydrogenation of 1-aryl-2-imidazol-1-yl-ethanones with formic acid using [(R,R)-TsDPEN]Ru(Cymene)Cl gave homochiral 1-aryl-2-imidazol-1-yl-ethanols. The hydrogenation was carried out under mild conditions at a molar substrate-to-catalyst ratio of 1000–2000. Bisphosphino Ru diamine complexes were found to be ineffective.


High-Temperature Polymer Electrolytes for PEM Fuel Cells: Study of the Oxygen Reduction Reaction (ORR) at a Pt–Polymer Electrolyte Interface

Z. LIU, J. S. WAINRIGHT and R. F. SAVINELL, Chem. Eng. Sci., 2004, 59, (22–23), 4833–4838

LINK doi:10.1016/j.ces.2004.09.024

A micro-band electrode cell was used to investigate the ORR for a Pt/polybenzimidazole–phosphoric acid system. The obtained Tafel plots were linear over four orders of magnitudes of kinetic current density. Both the kinetic parameters and the mass transport data were comparable to those of a Pt/phosphoric acid system.

Effects of Preparation Conditions on Performance of Carbon-Supported Nanosize Pt-Co Catalysts for Methanol Electro-Oxidation under Acidic Conditions

J. ZENG and J. Y. LEE, J. Power Sources, 2005, 140, (2), 268–273

LINK doi:10.1016/j.jpowsour.2004.08.022

Pt/C and Pt-Co/C were prepared by NaBH4 reduction of metal precursors. Citric acid was used as the complexing agent. The largest Pt-Co particles (12 nm) were formed in alkaline solution and the smallest particles (3.7 nm) in unbuffered solution. XPS showed that Pt is in the metallic state, whereas most of the Co is oxidised. The performance of the Pt-Co/C catalysts in MeOH electrooxidation under acidic conditions showed improvements over the Pt/C catalyst in both activity and CO-tolerance due to the Co addition.

Catalytic Activity of Pt–Ru Alloys Synthesized by a Microemulsion Method in Direct Methanol Fuel Cells

L. XIONG and A. MANTHIRAM, Solid State Ionics, 2005, 176, (3–4), 385–392

LINK doi:10.1016/j.ssi.2004.08.005

A microemulsion method was used to prepare nanostructured Pt-Ru/C catalysts (1) with different particle sizes. The electrochemical performances of (1) were evaluated in half cells with a mixture of 1 M H2SO4 and 1 M MeOH and in single cell DMFCs. (1) prepared with a water to surfactant molar ratio (W) of 10 exhibited the maximum mass activity with the least charge transfer resistance at an optimum particle size of ~ 5.3 nm. The mass activity decreases and the charge transfer resistance increases as the value of W decreases or increases from 10.

The Behavior of Palladium Catalysts in Direct Formic Acid Fuel Cells

Y. ZHU, Z. KHAN and R. I. MASEL, J. Power Sources, 2005, 139, (1–2), 15–20

LINK doi:10.1016/j.jpowsour.2004.06.054

Pd-based anode catalysts were used in DFAFCs. Power densities of 255 to 230 mW cm–2 were achieved at relatively high voltages of 0.40 to 0.50 V in formic acid (3.0 to 15.0 M) at 20ºC. A MEA with a Pd catalyst gave some decay in fuel cell performance over several hours. However, the performance can be completely recovered by applying a positive potential at the anode.


On the Perpendicular Anisotropy of Co/Pd Multilayers

J. I. HONG, S. SANKAR, A. E. BERKOWITZ and W. F. EGELHOFF, J. Magn. Magn. Mater., 2005, 285, (3), 359–366

LINK doi:10.1016/j.jmmm.2004.07.054

Co/Pd multilayers were deposited both at room temperature when thermally activated interfacial intermixing augmented the intentional alloying, and at 77 K. Stressed interfacial alloying is the dominant mechanism. Low temperature measurements indicated the presence of polarised Pd. The hard-axis magnetisation was modelled with a distribution of local perpendicular anisotropies which reflect local composition variations.

Synthesis and Characterization of CaRuO3 and SrRuO3 for Resistor Paste Application

K. GURUNATHAN, N. VYAWAHARE and D. P. AMALNERKAR, J. Mater. Sci.: Mater. Electron., 2005, 16, (1), 47–53

LINK doi:10.1007/s10854-005-4958-5

Ca and Sr ruthenates (1) were prepared by air heating admixtures of the respective carbonates of Ca/Sr and RuO2 at 500, 800 and 900ºC for 15 h. The solid-state reactions occurred at 700–800ºC. These powders still contained carbonate and hence were heated again at 900ºC for 15 h to eliminate the carbonate. The average particle size of (1) is ~ 200–400 nm. The resistor paste was formulated using (1) prepared at 800 or 900ºC and heat treated at 900ºC.