Thermolysis of Fe(CO)(5) and Co-2(CO)(8), dissolved in tetrahydronaphthalene, in the presence of aluminum trialkyl leads to uniform-sized Fe or Fe-Co nanoparticles, respectively. Subsequent treatment with very dilute oxygen forms a shell which protects the metallic or alloyed core of the particles against further oxidation. With the help of surfactants, for instance oleic acid or cashew nut shell liquid, the particles can be peptized in organic solvents like toluene or kerosene, resulting in magnetic fluids with extraordinary magnetic properties. The saturation of magnetization, M., of the fluids was determined by specific magnetization. The sizes and structure of the particles were investigated by transmission electron microscopy, and Moessbauer analysis showed that the core of the particles was metallic or alloyed, respectively. The particle surface termination was studied by X-ray photoelectron spectroscopy and Auger electron spectroscopy. Copyright (c) 2005 John Wiley & Sons, Ltd.

We present X-ray absorption spectroscopy (XAS) data, ultraviolet photoelectron spectra (Hei) and metastable impact electron spectra (MIES) of cobalt nanoparticles (typically 4 to 10 nm), prepared by CO2(CO)(8) thermolysis and pre-stabilized by smooth oxidation. We find that the particles consist of a core-shell system with a dominantly f.c.c. core and a shell in which Co-C and Co-O coordination is likely to occur. This corresponds well to the results from electron spectroscopy, that stabilization occurs via formation of (Co-COx) and (Co-O) groups formed during the oxidation procedure and appears sensitive to the reaction conditions. Peptization of the pre-stabilized particles with KorantinSH surrounds the particles with a dense organic shell, stable up to about 250degreesC. The carbonic acid molecules of the shell are oriented predominantly perpendicular to the surface of the particles, their carboxyl functional group linking the shell with the cobalt particles. This result is also supported by the XAS data, where it is observed that, during peptization, Co-C coordination is partly replaced by Co-O coordination. In order to arrive at these statements, auxiliary measurements on bare and gas-exposed cobalt films, also reported here, were required. Copyright (C) 2004 John Wiley Sons, Ltd.

Applied Organometallic ChemistryVolume 18, Issue 11 p. 566-572 Review A review—How nanoparticles emerged from organometallic chemistry Dedicated to Professor Helmut Bönnemann on the occasion of his 65th birthday S. S. Botha, S. S. Botha Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorW. Brijoux, Corresponding Author W. Brijoux [email protected] Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanyMax-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorR. Brinkmann, R. Brinkmann Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorM. Feyer, M. Feyer Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorH.-W. Hofstadt, H.-W. Hofstadt Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorG. Kelashvili, G. Kelashvili Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorS. Kinge, S. Kinge Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorN. Matoussevitch, N. Matoussevitch Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorK. S. Nagabhushana, Corresponding Author K. S. Nagabhushana [email protected] Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanyMax-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorF. Wen, F. Wen Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this author S. S. Botha, S. S. Botha Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorW. Brijoux, Corresponding Author W. Brijoux [email protected] Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanyMax-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorR. Brinkmann, R. Brinkmann Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorM. Feyer, M. Feyer Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorH.-W. Hofstadt, H.-W. Hofstadt Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorG. Kelashvili, G. Kelashvili Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorS. Kinge, S. Kinge Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorN. Matoussevitch, N. Matoussevitch Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorK. S. Nagabhushana, Corresponding Author K. S. Nagabhushana [email protected] Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanyMax-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this authorF. Wen, F. Wen Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz-1, D 45468 Mülheim an der Ruhr, GermanySearch for more papers by this author First published: 20 October 2004 https://doi.org/10.1002/aoc.808Citations: 9AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume18, Issue11Special Issue: XVth FECHEM Conference on Organometallic Chemistry, 10–15 August 2003, Zürich, SwitzerlandNovember 2004Pages 566-572 RelatedInformation

A novel, size-selective preparation route leads to air stable ‘monodisperse’ colloidal cobalt nanoparticles via the thermolysis of Co2(CO)8 in the presence of aluminum alkyls. X-ray absorption near edge structure measurements have proved that this preparation pathway provides long term stable zerovalent magnetic Cobalt particles. In addition, these measurements show that the chemical nature of the surfactant used exerts a significant influence on the stability and the local electronic and geometric structure of the analyzed nanoparticles.

A new PtAl phase, which is stable at room temperature under oxidizing conditions, has been synthesized at 200 °C and 5 MPa. X-ray studies reveal it to be different from the known polymorphs of PtAl, which crystallize in the FeSi and CsCl structure types. The crystal structure of the new PtAl modification is found to be isotypical with the low-temperature modification of PdAl. In situ high-temperature X-ray diffraction experiments in air were performed to study the thermal behavior of the new PtAl alloy. In the temperature range between 400 and 700 °C, Pt5Al3 forms as an intermediate phase. At higher temperature the alloy decomposes, resulting in the formation of platinum and Al2O3. The thermodynamic instability at high temperatures explains why this new modification has not been observed using contemporary metallurgic processes. Copyright © 2003 John Wiley & Sons, Ltd.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Ligand-stabilized noble metal nanoclusters, prepared by various chemical methods by different research groups in Japan and Germany, were characterized and examined by a common method for application to the catalysis for hydrogenation of olefins in homogeneous and heterogeneous systems in the liquid phase. The mean diameters of palladium, platinum, rhodium and Pd/Pt nanoclusters stabilized by various ligands range from 1.3 to 3.2 nm if prepared by a single reaction, and from 2.2 to 4.0 nm if prepared by a stepwise growth method. The Stokes radii of metal nanoclusters stabilized by surfactants range from 1.7 to 2.1 nm, suggesting a thickness of the protective layer from 1.1 to 1.4 nm, whereas those stabilized by polymers give much larger values, suggesting the formation of aggregates. The catalytic activities of the metal nanoclusters, evaluated by hydrogenation of 1,3-cyclooctadiene and methyl acrylate, depend mainly upon the particle size, i.e. the smaller the size, the higher the activity, However, a strongly interacting ligand like tetraoctylammonium halide and 1,10-phenanthroline can disturb the hydrogenation, In contrast, the activities of heterogeneous catalysts supported on charcoal depend strongly on the covering strength of the stabilizer. Copyright (C) 2001 John Wiley & Sons, Ltd.

Bimetallic Pt/Rh heterogeneous catalysts based on nanoscaled colloids supported on activated charcoal have been shown to exhibit maximum activity in hydrogenation of butyronitrile at a composition of 10 atom% Pt and 90 atom% Rh in the metallic core. This synergetic effect has to be traced back to the special structure of the bimetallic nanoparticles as elucidated by X-ray spectroscopy and CO chemisorption, The surface of Pt/Rh particles was investigated by CO chemisorption combined with IR spectroscopy. It has been shown that a Pt10Rh90 colloid exhibits the maximum ability to chemisorb CO, compared with other compositions, Based on the detection of the different types of bonding of CO molecules to the metal surface and the EXAFS results, our measurements reveal surface enrichment of the Rh component, The surface structure of the particles, which varies with the elemental composition, and the presence of a Pt-dominated core influence the CO chemisorption ability as well as the hydrogenation efficiency of the Pt/Rh colloid catalysts. Copyright (C) 2000 John Wiley & Sons, Ltd.

Pre-prepared nanometals stabilized by colloidal protective groups may be used as precursors for a new type of heterogeneous catalyst. Independent of the support the particle size, composition, and structure of colloidal metallic catalyst precursors may systematically be varied and adjusted to form the "active components" for special catalytic systems. Here we present an easy preparative access to a long neglected class of nanosized transition-metal colloids, i.e. nanometals stabilized by organo-aluminum compounds. As synthesized, this class of metal colloids show the characteristic properties of air- and moisture-sensitive organometallics. However, via the addition of modifiers, such as alcohols, carbonic acids or inorganic hydroxo-species, these organosols can easily be transferred into air-stable hydrosols readily dispersible in a broad variety of solvents including water. These modified precursors may be adsorbed on support materials at ambient temperature in order to prepare heterogeneous catalysts.

The reduction of [N(octyl)(4)](2)[CuCl2Br2] in organic solution (toluene) using Li[BEt3H] leads to colloidal Cu protected by cationic surfactants (NR4+). According to HRTEM (high-resolution transmission electron microscopy) and UV/vis data, the organosol is composed of relatively large Cu particles with diameters of between 5 and 10 nm. An in situ XANES (X-ray absorption near edge structure) investigation was performed for the first time during the colloid synthesis. Our measurements revealed the formation of an intermediate Cu+ state prior to the nucleation of the particles, thus giving direct insight into the mechanism of the colloid formation. The significant differences between the near edge structures of the bulk sample and the colloidal Cu have to be traced back to structural disorder in the lattice of this nanosized material.

A Bi-promoted charcoal-supported Pd–Pt oxidation catalyst prepared from colloidal NOct4Cl-stabilized Pd–Pt nanoparticles was investigated by means of X-ray photoelectron spectroscopy (XPS). Pd 3d, Pt 4f, Bi 4f, C 1s and O 1s spectra of the colloid, the supported colloid catalyst and a conventional charcoal-supported Pd–Pt/Bi coimpregnation catalyst (Degussa, CEF 196 RA/W) were measured. Both catalysts were explored unused (as-prepared) and after deactivation in the heterogeneous catalytic oxidation of glucose to gluconic acid. The spectra are analyzed to elucidate the higher starting activity of the Pd–Pt/Bi/C colloid catalyst, especially the role of the promotor Bi and the mechanisms leading to catalyst deactivation. The higher starting activity of the colloid catalyst is explained by the presence of completely reduced Pd and Pt, threevalent Bi and a smaller particle size in contrast to the conventional catalyst which contains partly oxidized Pd and a non-unique chemical state of Bi. The deactivation of both catalysts is suggested to be due to metal dissolution, particle growth and chemical poisoning.

Charcoal-supported Pd-Pt catalysts based on Pd-Pt/NOct4Cl colloidal alloys have superior activity and selectivity in the oxidation of glucose to gluconic acid compared with industrial heterogeneous Pd-Pt catalysts. According to transmission electron microscopy, X-ray diffraction/Debye function analysis, X-ray photoelectron spectroscopy, X-ray absorption near edge structure, and extended X-ray absorption fine structure analysis the chemical coreduction of PdCl2 and PtCl2 in the appropriate ratio with NOct4BEt3H yielded the alloyed Pd-Pt colloids in organic solvents. They are screened by the lipophilic NOct4Cl surfactant layer from coagulation and poisoning. TEM showed colloids of particle sizes in the range from 1.5 to 3 nm.

The reduction of MnBr2 . 2THF (THF = tetrahydrofuran) using K[BEt3H] yields the organosol [Mn . 0.3THF](x). According to the UV/Vis, ESR (electron spin resonance spectroscopy), HRTEM (high-resolution transmission electron microscopy), XPS (X-ray photoelectron spectroscopy) and XAS (X-ray absorption spectroscopy) data, this nanosized metal colloid consists of small THF-stabilized Mn-0 particles which show, in susceptibility investigations, a diminished magnetic coupling as deduced from the Weiss temperature, Theta = 96 K, The Neel temperature TN is likewise strongly reduced in comparison with the bulk value (95 K), The THF-stabilized Mn-0 particles exhibit superparamagnetism below 20 K, with a partial blocking at 10 K, and to our knowledge represent the first colloid consisting of particles of an elemental antiferromagnetic metal, (C) 1998 John Wiley & Sons, Ltd.

The formation of colloidal dispersions bf Mn is possible via the chemical reduction of MnBr2.2THF. The resulting hydrogen-free organosol is studied in detail bg-a combination of physical methods, including X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). it is concluded that the metal colloid consists of small Mn particles in the zero-valent stale. stabilized bq intact THF molecules, Nanostructured organosols of the early transition metal series are of interest as powerful additives for the activation of heterogeneous hydrogenation catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The performance of heterogeneous catalysts based on surfactant-stabilized palladium colloids is compared with conventional Pd/C and Lindlar catalysts in the partial hydrogenation of 3-hexyn-1-ol under optimized reaction conditions. The selectivity can be influenced by the protective shell as well as by the support and various promoters. The zwitterionic surfactant sulfobetaine-12 (N,N-dimethyldodecylammoniopropanesulfonate) appears to be best suited as a protective shell for highly selective palladium-colloid catalysts under the surfactants tested. The preferred support is CaCO3: the Pd(SB12) colloids supported on CaCO3 show the highest selectivities and activities of all tested catalysts. The best selectivity (98.1%) towards the desired cis-3-hexen-1-ol (leaf alcohol) is obtained with a lead-promoted palladium colloid supported on CaCO3. This catalyst is slightly (0.5%) better in selectivity and twice as active as a conventional Lindlar catalyst. © 1997 John Wiley & Sons, Ltd.

Preprepared nanometals stabilized by surfactants may be used as precursors for a new type of heterogeneous catalyst. Independent of the support these mono– or plurimetallic precursors may be optimized dependent on the size, composition, and structure of the particles. Further, the active metal surface may be shielded against poisons by the protective shell. In addition, doping agents may be used in order to enhance the catalytic performance. The cis–selective partial hydrogenation of 3–hexyn–1–ol giving leaf alcohol, a valuable fragrance, and the selective oxidation of glucose giving sodium gluconate are current examples for the application of supported nanometal colloids in fine chemicals catalysis.