Metal oxides binary

We shall be largely concerned here with the structures of metal oxides in the crystalline state since nearly all these compounds are solids at ordinary temperatures. We shall mention a number of suboxides, but we shall exclude peroxides and superoxides (and ozonates), for these compounds, in which there are 0-0 bonds, are included in Chapter 11. Little is known of the structures of metal oxides in the liquid or vapour states, though several have been studied as vapours (Table 12.1). The structures of the oxides of the semi-metals and of the B subgroup elements are described in other chapters. 

The crystal structures of metallic oxides include examples of all four main types, molecular, chain, layer, and 3D structures, though numerically the first three classes form a negligible fraction of the total number of oxides. The metals forming oxides with molecular, chain, or layer structures are distributed in an interesting way over the Periodic Table. 

The following generalizations may be found useful, but it should be remembered that like all generalizations they are subject to many exceptions, some of which will be noted later. 

Type of structure Formula type and coordination numbers of M and 0 Name of structure Examples 

Note this table does not distinguish between the most symmetrical form of a structure and distorted variants, superstructures, or defect structures for more details the text should be consulted. 

Whereas the development of crystalline, open-frameworks based upon silicates, phosphates and related materials has progressed at an ever increasing pace, the synthesis of simple binary oxides with periodic open stmctures has been less sue- 

The existence of these stable, open-frameworks in the specific case of manganese is presumably related to the high ligand field stabilization energy associated with the t2g electronic configuration of Mn +. This should render the materials kinetically stable with respect to their collapse into more condensed phases. It is also, no doubt, the reason why it has been possible to make stable mesoporous phases based upon Mn02, and indeed to remove the surfactant templates in order to access their microporosity [110]. 

Rayes-Gil et al. [93] reported an extensive study of nitrogen doping of hi203 powders and films synthesized by a sol-gel method. Large amounts of NH4CI or 

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F. Wells, Structural Inorganic Chemistry, 5th edn., Oxford University Press, Oxford, 1984 Chap. 12, Binary metal oxides, pp. 531-74 Chap. 13, Complex. oxides, pp. 575-625. 

P. Kofstad, Nonstoichiometry, Diffusion and Electrical Conductivity in Binary Metal Oxides, Wiley Interscience, New York (1972). 

Pinna, N., Garnweitner, G., Antonietti, M. and Niederberger, M. (2005) A general nonaqueous route to binary metal oxide nanocrystals involving a C-C bond cleavage. Journal of the American Chemical Society, 127 (15), 5608-5612. 

At present, the most promising binary metal oxides are Bi—Mo—O, Sn—Sb—O and Fe—Sb—O. It appears that these also form the basis of selective multi-component catalysts that are described in the literature or patent specifications. 

In addition to the aluminosilicate systems, a wide variety of other binary metal oxides exhibit surface acidities and acid-catalyzed activities that are greater when the oxides are chemically combined than would be the case for a physical mixture of the same oxides. The existence of this type of synergism is most easily explained in terms of Pauling s electrostatic valence rules (135). In a recent paper, Tanabe et al. (136) have extended such rules to account for the generation of acidity in 26 binary oxides. They make two postulates ... 

P. Kofstad. Nonstoichiometry, diffusion and electrical conductivity in binary metal oxides- New York Wiley-Interscience, 1972. 

Refs. [i] Wagner C (1930) Z phys Chem B 11 139 [ii] Kofstad P (1972) Nonstoichiometry, diffusion and electrical conductivity of binary metal oxides. Wiley-Interscience, New York [iii] RickertH (1982) Electrochemistry of solids. An introduction. Springer, Berlin [iv] Chebotin VN (1989) Chemical diffusion in solids. Nauka, Moscow... 

Figure 1. Binary metallic oxides (chain dotted lines), nitrides (dotted lines), and carbides (dashed lines) indicated on the periodic table.

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