Metal clusters structure

Parks E K, Welller B H, Bechthold P S, Hoffman W F, NIeman G C, Pobo L G and Riley S J 1988 Chemical probes of metal cluster structure reactions of Iron clusters with hydrogen, ammonia and water J. Chem. Rhys. 88 1622... 

An alternative approach is to relate variations in reactivity with metal clusters structures. Unfortunately even less is known about their geometric arrangement than their electronic structure. Suggestions made in the literature will be summarized and simple ideas of the degree of coordi native unsaturation will be presented. 

Transition-metal carbonyls, 16 58 Transition metal catalysts, 20 151-152 Transition-metal-catalyzed microwave-assisted reactions, 16 552 Transition metal-catalyzed reactions in ionic liquids, 26 878-897 Transition-metal clusters, structure of,... 

K. C. C. Kharas and L. F. Dahl, Ligand-stabilized metal clusters Structure, bonding, fluxionality, and the metallic state, Adv. Chem. Phys., 70, 1 (1988). 

For three-connect (and lower) main-group clusters, we concluded in Chapter 2 that a eve count is not particularly useful. However, metal cluster structures are not always easily analyzed in terms of metal connectivity. Bond distance criteria for the existence of a M-M bond are not as precise as those for an E-E bond. 

Exercise 3.12. The Au cluster, [Au6C(PR3)6]2+ exhibits an octahedral metal-cluster structure and contains an interstitial C atom. Justify composition and cluster geometry. 

Figure 1 Schematic representation of the Fe-protein (60 kD, 2 dimer) and the MoFe-protein (250 kD, a2fh. tetramer) of the Mo-nitrogenase. Outline of the electron transfer path through the metal clusters. Structure of the Fe4S4 cluster of the Fe-protein. Structure of the P-cluster (in two oxidation states) and of the FeMo-cofactor in the MoFe-Protein. Limiting stoichiometry for the function of Mo-nitrogenase...

High r factors are, however, not without some other complications since they imply porosity of materials. Porosity can lead to the following difficulties (a) impediment to disengagement of evolved gases or of diffusion of elec-trochemically consumable gases (as in fuel-cell electrodes 7i2) (b) expulsion of electrolyte from pores on gas evolution and (c) internal current distribution effects associated with pore resistance or interparticle resistance effects that can lead to anomalously high Tafel slopes (132, 477) and (d) difficulties in the use of impedance measurements for characterizing adsorption and the double-layer capacitance behavior of such materials. On the other hand, it is possible that finely porous materials, such as Raney nickels, can develop special catalytic properties associated with small atomic metal cluster structures, as known from the unusual catalytic activities of such synthetically produced polyatomic metal clusters (133). 

LIGAND-STABILIZED METAL CLUSTERS STRUCTURE, BONDING, FLUXIONALITY, AND THE METALLIC STATE... 

The presence of one or several nitrides is effective at modifying the metal cluster structure. Face bridging naked nitrides are not known but a nitrogen atom with a T-shaped coordination has been found in [Mo3(N )(0)(C0)4(C5H5)3]. Semi-exposed nitrides have been found in the species with four or five metal atoms they are invariably encapsulated into clusters of higher nuclearity. All the tetranuclear... 

The Investigation of Heavy Metal Cluster Structures in Powder Samples by the Radial Distribution Function Method... 

D.4 Ligand-stabilised metal clusters structure, bonding, fluxionality, and the metallic state... 

X-ray diffraction metal carbonyl clusters ionic clusters metal clusters structure of duster Strudural information (bond lengths and coordination numbers around a given metal atom) based on radial eledron distribution from X-ray data RED gives only metal-metiil, not metal-support or metal-adsorbate contributions. 

As it will be seen in next Section, metal cluster structures are closely related to the number of electrons and orbitals existing in the cluster core. In general. 

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