Clusters zirconium/oxygen

These two elements have very similar chemistries, though not so nearly identical as in the case of zirconium and hafnium. They have very little cationic behavior, but they form many complexes in oxidation states II, III, IV, and V. In oxidation states II and III M—M bonds are fairly common and in addition there are numerous compounds in lower oxidation states where metal atom clusters exist. An overview of oxidation states and stereochemistry (excluding the cluster compounds) is presented in Table 18-B-l. In discussing these elements it will be convenient to discuss some aspects (e.g., oxygen compounds, halides, and clusters) as classes without regard to oxidation state, while the complexes are more conveniently treated according to oxidation state. 

As follows from Fig. 2d, contrarily to the pure ceria sample, samples of mixed fluorite-like solid solutions retain molecular forms of oxygen (O2 [16]). The intensity of those bands is higher for samples containing calcium, fluorine and smaller amount of zirconium. It seems to correlate with the decreased ability of those systems to dissociate molecular oxygen due to a lower density of either highly unsaturated cations or clustered centers. 

The reaction of zirconium tetrachloride and hexamethylbenzene in the presence of aluminum and aluminum trichloride at 120°C produces a melt, which upon hydrolysis with water in the presence of methylene chloride, yields an organic-soluble species of composition [Zr3(C6(CH3)8-Cle]Cl. The brown product has a magnetic moment at 303°K of 2.04 B.M. Conductivity measurements have been interpreted in terms of the trinuclear cluster cation. It decomposes in nitrogen at 20°-30°C and is rapidly oxidized by oxygen 179). 

The pores of friendly nanomaterials could be used to store strong adds, even super acids, in some cases. Likewise, weak bases or strong bases could be stored for use as needed in killing or destroying advanced enemy toxins. In addition, the nanomaterial itself could be produced with acidic sites (metal ions and/or certain proton donors) built into the pore walls and crystal faces. For example, titanium or zirconium ions can serve as acid sites if adjacent to sulfate species. Likewise, the proton forms of some transition-metal oxygen-anion clusters (polyoxometalates or POMs ), like some metal oxides, are effective superacids in commercial processes. Polyoxometalates could be physically held within the pores or could be grafted onto the pore walls or onto the outer nanocrystal faces. Basic sites can also be built into the nanostructure, such as oxide anions near a metal cation vacancy. There are many other possibilities, such as sulfide substitution for oxide anions on the surface of the nanocrystals. 

On the (0001) face of a-alumina covered with one niobium, zirconium, molybdenum, ruthenium or palladium monolayer, Ohuchi and Koyama (1991) have shown that the metal d band is located in the energy range of the alumina gap. It is hybridized with the oxygen states of the valence band. In the series, more and more anti-bonding d states are filled, which yields results in agreement with the cluster calculations quoted above. 

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