High yield synthesis of Ru-Pt mixed-metal cluster compounds

The reaction of [PPN]2[Ru5C(CO)14] 1 or [PPN]2[Ru6C(CO)16] 2 [PPN+ = (PPh3)2N+] with Pt(II) compounds of general formula [PtX2Cl2] [X2 = (COD), (PPh3)2 and (PPh3)(CO)] (COD= 1,5-cyclooctadiene) have been investigated and the products of simple or double addition, viz. [Ru5PtC(CO)14(COD)] 3, [Ru5PtC(CO)14(PPh3)2] 4, [Ru5PtC(CO)15(PPh3)] 5, [Ru5Pt2C(CO)15(PPh3)2] 6, [Ru6PtC(CO)16(COD)] 7, [Ru6Pt2C(CO)15(COD)2] 8, obtained. The molecular and crystal structures of 3-8 have been established by single crystal X-ray analysis. Compounds 3-7 all contain an intact Ru core with Pt fragment(s) capping triangular or square faces. The resulting mixed-metal core is octahedral for the clusters Ru5Pt and face-capped octahedral for the clusters RunPtm (n = 5 or 6; m = 2 or 1). Only compound 8 did not follow this pattern, with the Pt fragments bridging two Ru-Ru edges of the otherwise unaltered Ru6C core

High yield synthesis and crystal structures of the Ru6-Sn cluster compounds [Ru6C(CO)16SnCl2] and [Ru6C(CO)16SnCl3]

Addition of two molar equivalents of SnCl4 to [Ru6C(CO)16]2- yields first the new [Ru6C(CO)16SnCl3]- cluster anion and then [Ru6C(CO)16SnCl2], the latter being also the single product of the direct addition of SnCl2 to [Ru6C(CO)17]

Synthesis and structure of two new high nuclearity Ru/Pt mixed-metal clusters

The reaction of the dianion [Ru5C(CO)14]12- with [PtCl2- (MeCN)2] in the presence of silica yields [Ru5PtC(CO)16] (1) and the new compound [PPN]2[Ru10Pt2C2(CO) 28] (2), while, in a related reaction, [Ru6C(CO)16]2- undergoes addition of [PtCl2(MeCN)2] to yield the cluster [Ru12PtC2(CO)32- (MeCN)2] (3). The high nuclearity compounds 2 and 3 have been fully characterized and their structures determined by single crystal X-ray analysis. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003

Towards the synthesis of a metal hamburger complex: The interaction of the PPh2(CH2)3Ph ligand with ruthenium clusters

Ruthenium clusters were reacted with the chelating arene ligand PPh2(CH2)3Ph. First, the phosphorous atom was coordinated to Ru6, Ru5 and Ru3 clusters, and the products of simple addition were fully characterised. A second (and third in the case of Ru3) equivalent of the ligand was then successfully added to the obtained species. Attempts to coordinate the 'dangling' benzene ring led to a Ru6 derivative, where a phenyl ring directly bound to the P atom reacted with the cluster, instead of the terminal one. The crystal structures of the compounds [Ru6C(CO)16PPh2(CH2) 3Ph] (3), [Ru3(CO)9{PPh2(CH2) 3Ph}3] (9), and [Ru6C(CO)13PPh2(CH2) 3Ph] (10) were determined by X-ray diffraction. The former two consist of the intact cluster core with either one or three ligands bonded via the P atom, while the latter has additionally one of the phenyl rings on the phosphorous connected to the cluster in a η6 bonding mode. © 2003 Elsevier Science B.V. All rights reserved

Single step, solvent-free processes: examples and prospects

An outline is given of some of the options now available — and likely to be of growing importance — for various of ways in which inorganic catalysts may be developed to effect industrially important chemical reactions in environmentally more acceptable means. One major goal is to devise ways of producing in situ (within the sphere of reaction) aggressive oxidants especially those that are environmentally hazardous. Two specific examples are cited: 1) one involves hydroxylamine, generated in a benign fashion, so as to effect the ammoximation of cyclohexanone to its oxime and -caprolactam; 2) the other involves the Baeyer—Villiger reaction (for converting cyclic ketones to lactones) via perbenzoic acid. The role of supported bimetallic catalysts in solvent-free hydrogenations (especially of polyenes) is also highlighted

Temperature threshold and water role in CVD growth of single-walled carbon nanotubes

An in-depth understanding of the growth process of single-walled carbon nanotubes is of vital importance to the control of the yield of the material and its carbon structure. Using a nickel/silica (Ni/SiOx) catalyst, we have conducted a series of growth experiments with a chemical vapor deposition (CVD) system. We find that there is a temperature threshold in the CVD process, and if the reaction temperature sets above this threshold, there will be no growth of the nanotubes. Moreover, we find that in association with this temperature effect, water plays an important role in the promotion or termination of the growth of single-walled carbon nanotubes

Gold supported on mesoporous titania thin films for application in microstructured reactors in low-temperature water-gas shift reaction

Au (1 wt.%)/TiO2 catalytic thin films were prepared on a surface-modified titanium substrate for application in a water-gas shift (WGS) microstructured reactor. Au-containing mesoporous titania films were synthesized using Pluronic 127 surfactant as a structure directing agent and titanium tetrabutoxide as titania source. Colloidal gold nanoparticles of 4 nm diameter were added to the synthesis sol prior to spin-coating. The resulting thin films were characterized by X-ray diffraction, transmission electron microscopy, ethanol adsorption–desorption isotherms and spectroscopic ellipsometry. Catalytic activity and selectivity were measured for the WGS reaction at temperatures between 220 and 290 °C. The reaction rate measured at CO conversions of below 10% was similar to that reported for gold supported on mesoporous titania and on ceria modified mesoporous titania pelletized catalysts prepared via deposition–precipitation

The synthesis and characterisation of the cluster dianion [PtRu5C(CO)15]2- and its reactions with Au and Pt cationic fragments produced in situ

The neutral mixed-metal cluster [PtRu5C(CO)16] was reduced by KOH in methanol to give [Ph4P]2 [PtRu5C(CO)15] 1 in 84% yield. Reaction of 1 with Au(PPh3)Cl afforded the gold derivative [PtRu5C(CO)15(AuPPh3)2] 2. Other reactions of 1 with [Pt(COD)Cl2] and [Pt(CO)(PPh3)Cl2] in the presence of silica yielded the new mixed-metal cluster compounds [Pt2Ru4C(CO)13(COD)] 3, [Ph4P]2[Pt3Ru10C2 (CO)32] 4, [Pt4Ru5C(CO)16(PPh3)3] 5, [PtRu4C(CO)13 (PPh3)] 6 and [Pt2Ru4C(CO)14(PPh3)] 7. Compounds 1-7 were characterised spectroscopically and the molecular and crystal structures of compound 1-5 were determined by single crystal X-ray crystallography