Transition-metal-oxide cluster

The reactions of MeOH with some transition metal oxide cluster anions [M O J, where M = Mn, Fe, Co, Ni, Cu n = 1,2 x = 2—4, have been studied (254). The [M03] anions were unreactive toward MeOH, unlike [Nb03]. The addition of the hydrogen molecule to the other cluster anions was the common reaction yielding the following transformations,... 

A review of recent research, as well as new results, are presented on transition metal oxide clusters, surfaces, and crystals. Quantum-chemical calculations of clusters of first row transition metal oxides have been made to evaluate the accuracy of ab initio and density functional calculations. Adsorbates on metal oxide surfaces have been studied with both ab initio and semi-empirical methods, and results are presented for the bonding and electronic interactions of large organic adsorbates, e.g. aromatic molecules, on Ti02 and ZnO. Defects and intercalation, notably of H, Li, and Na in TiC>2 have been investigated theoretically. Comparisons with experiments are made throughout to validate the calculations. Finally, the role of quantum-chemical calculations in the study of metal oxide based photoelectrochemical devices, such as dye-sensitized solar cells and electrochromic displays, is discussed. 

The 3d transition metals are widely employed as catalyst and catalyst support materials in industry [3]. To gain insight into how these support materials and the catalyst support interaction influence catalytic activity, GIB-MS experiments were undertaken in our laboratory to determine the structural characteristics of cobalt oxide and nickel oxide clusters as well as their reactivity with CO. CID experiments were conducted employing Xe gas to elucidate the structural building blocks of the larger clusters. These studies provided insight into how additional (i-electrons impact the dissociation pathways and bonding motifs of 3d transition metal oxide clusters. Reactivity studies with CO were carried out, which revealed that oxide clusters composed of different 3d metals have specific stoichiometries which are most active for CO oxidation. 

Zemski KA, Justes DR, Castleman AW Jr (2001) Reactions of group V transition metal oxide cluster ions with ethane and ethylene. J Phys Chem A 105 10237... 

During the compilation of this book, an important member and friend of the catalysis and surface science community, J. Mike White (University of Texas, Austin and Pacific Northwest National Laboratory) suddenly passed away. Mike was to author two chapters in this book, Photocatalysis at Adsorbate-Single Crystal Metal and Metal Oxide Interfaces and Supported Early Transition Metal Oxide Clusters Structural and Catalytic Properties. It is truly unfortunate that we will not be able to read his chapters they would have been first rate. I thank Professor Hicham Idriss for including a section on photocatalysis on TiO single crystals in Chap. 7 and Professors Gunther Rupprechter and Simon Penner for then-chapter on metal oxide cluster catalysis (Chap. 17). 

M. I. Khan, Novel extended solids composed of transition metal oxide clusters, J. Solid State Chemistry. 152 105(2000). 

The surfaces of metal oxides and their H2 chemisorption characteristics have been far less studied than the surfaces of elemental metals and semiconductors [113,133]. Cation surface states are formed on ideal oxide surfaces at about 2 eV below the bottom ofthe conduction band. The charge of the surface ions is found to be reduced compared with that of the bulk ions and this leads to an enhanced co valency at the surface. The reduction amounts to less than 10 % for oxides of simple metals such as MgO and to 20-30% for transition metal oxides. Cluster and slab calculations reveal that special surface state bands with metallic character can be formed on polar surfaces by charge compensation effects. To what extent the metallic band accounts for special catalytic activity is not yet known [114]. 

C-H Bond Activation by High-Valence Transition Metal Oxide Clusters... 

Synthesis of Organically Modified Transition Metal Oxide Clusters 59... 

The aforementioned studies of rare earth oxide cluster ions focused on formation and structural aspects, and apart from the supposed ion chemistry occurring during synthesis, only recently have reactivity experiments with different small molecules been pursued, mainly due to the work of Ding s group, following inventive work by Castleman and coworkers with transition metal oxide clusters (Castleman, 2011 Johnson et al., 2008). Rare earth oxides are widely used as catalysts or catalyst supports investigating the bonding... 

It is clear that aromaticity and antiaromaticity could be very useful concepts in explaining structure, stability, and other molecular properties of isolated and embedded clusters of transition metals and transition metal oxide clusters. The chemical bonding in transition metal clusters can come from s-AOs, p-AOs, and d-AOs, and can be expressed as a variety of multiple aromaticities and antiaromaticities as well as of conflicting aromaticities. 

The early transition-metal-oxide clusters do not have metal-metal bonds, but the metals are linked by oxygen atoms that can also occupy non-bridging terminal positions. They are the heteropolyacids and their salts, the heteropolymetallates. These clnsters have been extensively developed in France by Sonchay s school now very active, in the United States by Pope and in Germany by Muller. - They have many kinds of structures, but the most known ones in oxidation catalysis are Keggin structures (XM i204o) in which the central atom X = Si, Ge, ... 

A kind of more complicated metal oxide clusters, cerium oxide clusters are studied by Sierka s group. Ce202", Ce304 , and (Ce02)m CeO (m = 0-4) are unambiguously determined by a combination of GA-DFT method and infrared vibrational predissociation spectroscopy of the cluster-rare gas atom complexes. The most stable structures of even small gas-phase aggregates of cerium oxide with 2-5 cerium atoms show structural motifs reminiscent of the bulk ceria. This is different from main group and transition metal oxide clusters, which often display structural features that are distinctly different from the bulk structure. 

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