Group 14 elements oxides

The binary representation is applicable to various other oxide materials. However, an important distinction can be made between borates and other main group element oxide systems, such as aluminates and silicates. In the latter systems cations predominantly reside at sites created by the demands of rigid anionic oxide frameworks. Although some degree of structural control may be obtained by varying cations or by use of template synthesis, the oxide frameworks of these systems tend to be relatively inflexible in comparison with... 

Metal oxides display a variety of unique physical and chemical properties and are employed in numerous technological applications (Table 7-1). Chemical vapor deposition has been used widely for the preparation of metal oxide thin films [10, 13]. The following section summarizes the preparation of several transition metal and main group element oxides by CVD. 

Numerous main group element oxides that have been prepared by CVD techniques have been described in previous chapters. Thus, below is summarized information relating to a few metal oxides which were not discussed. 

Iron carbonyl clusters incorporating Se or Te have been synthesized by reacting methanolic KOH solutions of Fe(CO)s with the main group element oxides (Scheme 81). Both complexes [E Fe(CO)4)3] lose CO at room temperature in THF solution to form the closed tetrahedral clusters, but in the case of selenium, the loss is so rapid that isolation of the pure complex without Fe-Fe bonds is very difficult. 

Nitrogen is unusual in forming so many oxides. The acidity of the Group V oxides falls from phosphorus, whose oxides are acidic, through arsenic and antimony whose oxides are amphoteric, to the basic oxide ofbismuth. This change is in accordance with the change from the non-metallic element, phosphorus, to the essentially metallic element, bismuth. The +5 oxides are found, in each case, to be more acidic than the corresponding + 3 oxides. 

When the characteristic element is partially or wholly present in a lower oxidation state than corresponds to its Periodic Group number, oxidation numbers are used for example, [O2HP—O—P03H] , dihydrogendiphosphate(III,V)(2—). 

R)C2B4H ions and appropriate main group element haUdes, have stmctures containing central main group elements iu the 4+ oxidation states similar to the bis-dicarboUide sUicon sandwich compound. TThe stmcture of the sUicon sandwich compound commo- ](GH.])fi fZ, fri fii is shown iu Figure 27. 

Dithiocarbamates of transition group elements in unusual oxidation states. J. Willemse, J. A. Cras, J. J, Steggerda and C. P. Keijzers, Struct. Bonding (Berlin), 1976, 28, 83-126 (195). 

The product of the second reaction is sodium aluminate, which contains the alumi-nate ion, Al(OH)4. Other main-group elements that form amphoteric oxides are shown in Fig. 10.7. The acidic, amphoteric, or basic character of the oxides of the d-block metals depends on their oxidation state (Fig. 10.8 also see Chapter 16). 

Several preparative methods do not use elemental mixtures. Group IIA-Pt intermetallic compounds have been prepared by reacting platinum metal with the group-IIA oxide under hydrogen or ammonia at 900-1200 C. Beryllium metal reacts with neptunium fluoride under vacuum at 1100-1200°C to form BC 3Np. 

Dithiocarbamates of Transition Group Elements in Unusual Oxidation States... 

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