Oxides clusters

France M R, Buchanan J W, Robinson J C, Pullins S FI, Tucker J T, King R B and Duncan M A 1997 Antimony and bismuth oxide clusters growth and decomposition of new magic number clusters J. Phys. Chem. A 101 6214... 

Kaiser B, Bernhardt T M, Kinne M, Rademann K and Fleidenreich A 1999 Formation, stability, and structures of antimony oxide cluster ions J. Chem. Phys. 110 1437... 

Mode (D2 symmetry) Oxidized cluster Reduced cluster Mode (C2 symmetry)... 

Overview of the Chemistry of Niobium Chloride and Niobium Oxide Cluster Compounds 83... 

Figure 5b. Variation in the magnetic properties of metal clusters are investigated by measuring the depletion of a highly collimated cluster beam by an inhomogeneous magnetic field. Fe clusters and their oxides (FexO and Fex02) at several applied fields. The uniform depletion of Fe clusters indicates that their magnetic moments increase approximately linearly with number of atoms, as would be anticipated for incipient ferromagnetic iron. Unexpected, however, is the much larger depletion of iron oxide clusters.

As a particular highlight in the V-oxide-Rh(l 11) phase diagram, we mention the spontaneous formation of quasi-zero-dimensional V-oxide clusters, which are illustrated in Figure 6.9a and b [4,19]. These star-like clusters form at very low V coverages... 

Taking into account the high Mo content (5 - 7%wt) of V-Mo-ZSM-5 samples and to the conclusions of the different characterisations, we may assume that die most of molybdenum and vanadium are well dispersed on die surface of ZSM-5 in form of small oxide clusters. 

Synthetic routes to metalloboranes are briefly summarized. Two specific aspects of the field are selected for more detailed comment (i) the occurrence of exopolyhedral cycloboronation of P-phenyl groups (ii) oxidative cluster closure reactions. These topics are illustrated by reference to reactions of closo-BioHio nido-B9H12 and arachno-BoHiU" with a variety of Ir1 complexes, and several novel metalloborane cluster geometries (as determined by X-ray diffraction analysis) are described, notably nido-TIr(BoHi )H (PPh3)2], i so-ni do-[ IrC(OH)B8H6(OMe) (CgH PPh )... 

Recently, it has been reported that a novel calcination procedure relying on nitric oxide gas in lieu of air also results in smaller cobalt crystallites over silica supports.15 17 The idea is to use a less oxidative gas to prevent rapid decomposition of the nitrate precursor during thermal nitrate decomposition, which has been observed when 02 is present.17 As a result, the mobility of the precursor on the oxide carrier surface is hindered, resulting in a smaller average Co oxide cluster... 

Cover Illustration Atomic force microscopy image of molybdenum oxide particles on flat, silicon dioxide substrate, which serves as a model system for a supported catalyst. The area shown corresponds to one square micrometer the maximum difference in height is approximately 10 nanometer. The superimposed curve is the secondary ion mass spectrum of the model catalyst, showing the caracteristic isotopic patterns of single molybdenum ions and of molybdenum oxide cluster ions. 

Cf produces two fission products that travel in opposite directions. If one projectile hits the sample, ions will be produced. These ions may then be focused and measured by TOF MS. The other projectile may be used to measure the start of the ionization process. This method has been used to study the ions produced from the ionization of metal complexes such as cadmium thiolates (33) and lanthanide phthalocyanine complexes (34). This method has also been used on metal oxides such as La203 to produce metal oxide cluster ions (35). 

Gas-phase metal oxide cluster cations have become increasingly interesting because of the possibility that a controlled reaction of size selected clusters might shed some light on condensed-phase catalysts. The possibility of producing small clusters in the condensed phase from deposition of gas-phase clusters has also been a driving force in the study of the reactivity of gas-phase ions. 

The reactions of the vanadium oxide cluster cations with CCI4 were of three types (248). The small cluster ions reacted by transfer of a chloride ion. The larger clusters starting with the V4OJ+ series reacted by the addition of a chlorine atom to the cluster or the loss of one oxygen atom and the addition of two chlorine atoms. 

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