Ruthenium-platinum cluster

Platinum-ruthenium carbonyl clusters, characteristics, 8, 419 Platinum-sulfur bonds, in platinacycles, 8, 505 Platinum-thallium carbonyl clusters, characteristics,... 

In view of the expectation that platinum will concentrate in the surface of platinum-iridium clusters, we might anticipate that platinum and iridium would segregate from one another to an increasingly greater extent as the clusters become smaller and the ratio of surface atoms to total metal atoms increases (48). When the ratio is equal to 0.5 for clusters containing 50% each of platinum and iridium, one can visualize a situation in which essentially all of the platinum is present in the surface and all of the iridium in the interior. There would then be a close resemblance to the ruthenium-copper clusters (2,31) discussed earlier. 

Rh, Pt, etc. Plans are under way in this laboratory for studies of the static and dynamic structure of CO on binary and ternary alloys (e.g., ruthenium/platinum/tin) in methanol for fuel-cell applications. Such alloys display enhanced resistance to CO poisoning, and the nature of this resistance is appropriate for NMR investigation. For example, Pt-CO bonding information such as Pt-C connectivities, CO orientation and clustering, are accessible by Ti, T2, isotope dilution, and related techniques. In fact, essentially all of the techniques used in the past 20 years to study the solid-gas interface should now be applicable to NMR-electrochemistry, with the added bonus of potential control. 

The use of polymer-stabilised colloidal platinum clusters (containing cinchoni-dine) in acetic acid provides up to 97.6% ee in the reduction of methyl pyruvate (MeCOCOzMe). Polyvinylpyrrohdine is used as the polymer, and the particle size is small. The use of nanoparticles as a support for catalysts is an attractive concept owing to the large surface areas of these materials. However, such supported catalysts of this type are often difficult to recover. Hu and coworkers have achieved the immobilisation of ruthenium(phosphine)( 1,2-diamine) catalysts onto... 

The generation of metal nanoparticles is based on the use of M-CO complexes. This approach has been successfully used in generating ruthenium cluster-like, as well as platinum cluster-like compounds. The chemistry seems simple, since it is like a pyrolysis process made in a solvent in mild conditions. This latter can be acpieous or a partially aqueous one. The reaction can be summarized as follows ... 

Watanabe, M., Uchida, M. Motoo, S. Preparation ofhighly dispersed platinum 4-ruthenium alloy clusters and the activity for the electrooxidation of methanol. J. Electroanal. Chem. Interfacial Electrochem. 229 (1987), pp. 395 06. 

Non-ionic thiourea derivatives have been used as ligands for metal complexes [63,64] as well as anionic thioureas and, in both cases, coordination in metal clusters has also been described [65,66]. Examples of mononuclear complexes of simple alkyl- or aryl-substituted thiourea monoanions, containing N,S-chelating ligands (Scheme 11), have been reported for rhodium(III) [67,68], iridium and many other transition metals, such as chromium(III), technetium(III), rhenium(V), aluminium, ruthenium, osmium, platinum [69] and palladium [70]. Many complexes with N,S-chelating monothioureas were prepared with two triphenylphosphines as substituents. 

Because of- the similarity in the backscattering properties of platinum and iridium, we were not able to distinguish between neighboring platinum and iridium atoms in the analysis of the EXAFS associated with either component of platinum-iridium alloys or clusters. In this respect, the situation is very different from that for systems like ruthenium-copper, osmium-copper, or rhodium-copper. Therefore, we concentrated on the determination of interatomic distances. To obtain accurate values of interatomic distances, it is necessary to have precise information on phase shifts. For the platinum-iridium system, there is no problem in this regard, since the phase shifts of platinum and iridium are not very different. Hence the uncertainty in the phase shift of a platinum-iridium atom pair is very small. 

Nashner MS, Frenkel Al, Adler DL, Shapley JR, Nuzzo RG. 1997. Structural characterization of carbon supported platinum-ruthenium nanoparticles from the molecular cluster precursor PtRu5(CO)i6. J Am Chem Soc 119 7760. 

The Pt2Ru4(CO)i8 cluster reacts with H2 to form Pt3Ru6(CO)2i(/i3-H)-(jt-H)3 in which the platinum and ruthenium atoms are arranged in triangular layers of the pure elements.10 This complex can be converted to Pt3Ru6(CO)20(/i3-C2Ph2X/i-H)2 by reaction with diphenylacetylene.10 The latter complex was found to be an active catalyst for the hydrogenation... 

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