Oxides and Sulphides

Iron metaniobates(iv) with structures of the natural minerals, ilmenite and pseudo-brookite have been prepared by direct reaction of the oxides under vacuum at 1000—1100°C. The compounds are stable in air up to 500°C, but are oxidized at higher temperatures.326 a-Sr3Fe07 x has been found to be isostructural with Sr3Ti07.327 Synthesis and thermal decomposition of iron(m) normal selenite mono-or tri-hydrate, Fe203,3Se02,xH20 (x = 1 or 3) have been reported.328 

Cu9Fe9S16, has been reported,331 and La32.66Fe11S60 has been found to contain 12 non-equivalent lanthanon sites, four of which are not completely filled, involving seven- or eight-co-ordination and four iron sites with octahedral co-ordination. Two other iron sites have occupancies of O.5.121 Fe2P2X6 (X = S or Se) form layer lattices with double layers of X atoms. Iron atoms and pairs of phosphorus atoms occupy octahedral sites.332 

The economic significance of iron has resulted in great interest over the years in the products of its oxidation, and more recently in the vast ranges of ternary oxides such as spinel ferrites which have been commercially exploited in their own right. 

The following subdivisions will be considered (i) binary oxides (ii) spinel oxides (iii) other ternary oxides (iv) iron(IV) oxides (v) chalcogenides (vi) silicate minerals and (vii) lunar samples. 

The last two sections listed are included here for convenience, although there are significant differences from the other sections in behaviour of the cations. 

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Fig. 7.78 Thermodynamic stability diagram for some oxides and sulphides at 1 000 K (after...

Two contrasting conclusions have been reported in the reactions of lithium aluminium hydride in THF with phosphine oxides and phosphine sulphides respectively. The secondary oxide, phenyl-a-phenylethylphos-phine oxide (42), has been found to be racemized very rapidly by lithium aluminium hydride, and this observation casts some doubt on earlier reports of the preparation of optically active secondary oxides by reduction of menthyl phosphinates with this reagent. A similar study of the treatment of (/ )-(+ )-methyl-n-propylphenylphosphine sulphide (43) with lithium aluminium hydride has revealed no racemization. These results have been rationalized on the basis of the preferred site of attack of hydride on the complexed intermediate (44), which, in the case of phosphine oxides (X = O), is at phosphorus, and in the case of the sulphides (X = S), is at sulphur. Such behaviour is comparable to that observed during the reduction of phosphine oxides and sulphides with hexachlorodisilane. ... 

A novel demonstration of the strength of the Si-O bond relative to the Si-S bond was provided during attempts to obtain the oxide and sulphide of Bu MeP-NfSiMea).. ... 

In 1944 Ellingham compiled, for the first time, diagrams depicting the temperature dependence of the standard free energies of formation of numerous oxides and sulphides. In the discussion presented here, attention will be confined to the oxide reaction... 

The electrochemical intercalation/insertion is not a special property of graphite. It is apparent also with many other host/guest pairs, provided that the host lattice is a thermodynamically or kinetically stable system of interconnected vacant lattice sites for transport and location of guest species. Particularly useful are host lattices of inorganic oxides and sulphides with layer or chain-type structures. Figure 5.30 presents an example of the cathodic insertion of Li+ into the TiS2 host lattice, which is practically important in lithium batteries. 

Of mineral origin inorganic chemistry is the study of all chemical elements and compounds, except carbon and its compounds certain simple carbon compounds, e.g., oxides and sulphides,... 

Tenorite (CuO Cu = 80%, SG = 6.5) is usually present in mixed copper oxide and sulphide ore. The flotation properties of tenorite are similar to that of cuprite. 

The kinetics of decomposition of certain inorganic oxides and sulphides and a few related compounds are reviewed in this chapter. Discussion is limited to the gas and liquid phase and to the reactions of neutral species. Accordingly, reactions in ionizing solvents have been excluded. The decompositions of the following compounds are considered C302, CO, C02, CS2, COS, CSe2, COSe, N20,... 

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