Silicides, and Germanides

Carbides, Silicides, and Germanides. The standard heat of formation and the dissociation energy of TiCjCg) have been determined as — 730 9 and 160 + 8 kJ mol , respectively, using the mass spectrometric Knudsen effusion technique. The standard heat and entropy of formation of TijSijis) have been reported as — 580 kJ moP and 272 e.u., respectively. A thermodynamic analysis of the co-reduction of TiOj with Si02 by carbon at elevated temperatures has shown that the formation of TiSi is more probable than TiSij. Phase equilibria in the Ti-Nb-Ge ternary system have been investigated.  

Titanium(ii).—Pulse radiolysis of aqueous solutions of titanium(iii) containing formic acid affords Ti via reduction of Ti by -C02H. Density determinations of molten NaCl solutions (800—950 °Q of TiCl2 suggest that substantial amounts of [TiClj] are formed in such media. The d-d spectrmn of Ti ions isolated in NaCl crystals have been obtained, and absorption maxima 

Yamamoto, S. Go, M. Ookawa, M. Takahishi, S. Ikeda, and T. Keii, Bull. Chem. Soc. Japan, 

Oxidative additions of alkyl and acyl halides to [(K-Cp)2Ti(CO)2] affording Ti derivatives have been reported (p. 25). Titanocene has been shown to reduce a variety of organic molecules including alcohols, aldehydes, ketones, and organic halides. 

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Silicides and Germanides The electrolysis of melts containing Na2SiF6 (or Na2Ge20s) and transition metal (Cr, Mn, Fe, Ni, etc.) oxides or fluorides often resulted in the synthesis of the silicides (or germanides). 

Clathrate silicides and germanides Nosean-sodalite felspathoids... 

Carbides, Silicides, and Germanides. Single crystals of TiC were obtained from the reaction... 

There exist a large number of ternary silicides and germanides (see Villars and Culbert 1985), but magnetic data are available only for a few of them (see below). 

Clathrate Si and Ge compounds can be prepared by thermal decomposition of alkali-metal silicides and germanides of the general formula MSi or MGe (M = alkali metal) . Thermal treatment is performed under a slow argon flow (3 nL/mn) or under a high vacuum (10 n/m ). The required experimental conditions are listed in Table 1. 

Table 1. Conditions of Formations of Silicon and Germanium Clathrates by Thermal Decomposition of Alkali Silicides and Germanides MSi and MGe (From Ref. 6) ...

These conditions are easier to realize than the previous ones, since they do not require the intermediate, dangerous preparation of the highly reactive silicides and germanides, MSi and MGe. 

Silicides and Germanides of Alkali Metals from the Elements... 

Fig. 273. Iron bombs used in the preparation of alkali metal silicides and germanides . 4—bomb for preparation of Rb and Cs compounds 5—bomb for the Na and K compounds, b—Iron bomb h iron screw-on cap t/—corundum crucible —copper gasket I —iron cone.

Fig. 274. Filling (transfer) apparatus for preparing alkali metal silicides and germanides b—iron bomb d—silicon or germanium /—ampoule containing alkali metal.

The majority of metal phosphides have a metal arsenide analogue which they usually resanble in properties and structure (Table 8.2). Metal phosphides, arsenides and nitrides not infrequently exhibit properties similar to those of metal carbides, silicides and germanides. Some metal phosphides are very useful semiconductors, while others shew superconduction or a variety of magnetic properties. Light-emitting diodes (LEDs) and nanostructured materials are other modem applications (Chapter 12.19). 

Gladyshevsky, E.I., 1971, Crystal Chemistry of Silicids and Germanids (Metallurgia, Moscou) p. 198. 

It appears that in aluminides and gallides the prismatic sites are occupied by the T atoms, whereas in silicides and germanides they are occupied by M atoms. In the complete list of ZrNiAl-type compounds given below the type heading, all RTM compounds have been listed that were described in the literature as having ZrNiAl-type, ordered FejP-type, or simply FejP-type. In many cases the order has not been studied or a certain order was assumed without proof and without testing the other possibility for ordering of the T and M atoms. 

It should be mentioned that silicides and germanides with composition 7533 are... 

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