Silicon disulfide

Silicon disulfide Al2S3+Si02 at 1200°C J >Si Fibrous crystals. Sublimes without melting. Attacked by water ... 

If the covalent bonds connect elements of the structure along one dimension only, as in silicon disulfide, it may be desirable to consider the substance as a polymer. This will certainly be appropriate if the valence structure supersedes whatever crystalline arrangement prevails, i.e., if the substance can be melted without seriously disrupting the continuity of the interunit connections. 

The acidic character of silica is shown by its reaction with a large number of basic oxides to form silicates. The phase relations of numerous oxide systems involving silica have been summarized (23). Reactions of silica at elevated temperatures with alkali and alkaline-earth carbonates result in the displacement of the more volatile acid, C02, and the formation of the corresponding silicates. Similar reactions occur with a number of nitrates and sulfates. Silica at high temperature in the presence of sulfides gives thiosilicates or silicon disulfide, SiS2. 

Energy also is involved in transitions from one allotropic form to another, or from one crystal form to another. To change a mole of red phosphorus to yellow phosphorus, we must supply 4.22 kilocalories (AHT = +4.22 kcal/mole), and when 1 mole of yellow silicon disulfide changes to white silicon disulfide, 3.11 kcal is liberated (AHT = -3.11 kcal/mole). 

Replacement of the carbonyl oxygen atom by sulfur may be effected by heating with phosphorus pentasulfide (49JCS2142), boron sulfide or silicon disulfide which gives high yields under mild conditions, as, for example, in the synthesis of 7-methoxy-2-methylchromene-4-thione (438) (69JCS(C)2192). Such compounds are more easily converted into their oximes or hydrazones than the oxygen compounds. 

The reaction of 59 with sulfur is somewhat more complicated (Scheme 19). At low temperatures, an intermediate is observed with a 29Si NMR chemical shift of +122.6 ppm this deshielded value is consistent with the silanethione, 69. Wanning of the solution produces the 4-ring dimer, 70. But when the reaction is carried out at room temperature this intermediate is not observed, and the major product is the trisilicon compound 71 in which a molecule of diimine has been lost from the central silicon374. The structure of 71 is somewhat similar to that of solid silicon disulfide. 

It is interesting to note that silicon disulfide, SiS2, is even more closely analogous to the flexible organosiloxane chain polymers than is the oxide. In the crystal structure of the sulfide as determined by X-ray analysis, the silicon atoms are linked to two pairs of sulfur... 

It is impossible to tell at this time whether the spacings and configuration of the polyorganosiloxanes follow those of silicon dioxide or silicon disulfide, or neither of them. Such comparisons must await X-ray analysis of the polymeric structure. Once the interatomic distances and the approximate bond angles are known for several organo-siloxane chains, it tnay become possible to plan stronger and better polymeric structures instead of continuing to seek them on a purely empirical basis. 

Most nonmetallic (or metalloid) elements form sulfides that if not molecular, have polymeric structures involving sulfide bridges. Thus silicon disulfide (12-VI) consists of infinite chains of SiS4 tetrahedra sharing edges, whereas the isomorphous Sb2S3 and Bi2S3 (12-VII) form infinite bands that are then held in parallel strips in the crystal by weak secondary bonds. 

Silicon disulfide does form fibrous crystals of this sort. 

Cyclodisilathianes may decompose thermally to silicon disulfide and silicon derivatives (R4Si) of the substituents or to trimers of R2Si=S. 1503,1532 Thermolysis of 636 with 2,2,3,3-tetramethyl-l,4-dithia-2,3-disilacyclo-hexane gives an equimolar mixture of 2,2-dimethyl-l,3-dithia-2-silacyclopentane and 2,2,4,4,5,5-hexamethyl-l,3-dithia-2,4,5-trisilacyclopentane analogous reac-... 

I.. sodium chloride [NaCI] 2. silicon disulfide [SiS ] 3. uranyl dilluoride [UO2F,]... 

GAB/ALV] Gabriel, H., Alvarez-Tostado, C., Silicon disulfide and silicon diselenide, J. Am. Chem. Soc., 74, (1952), 262-264. Cited on page 208. 

An interesting topological effect is the increased terminal chlorination of fatty acids when they are adsorbed and aligned on alumina Silicon disulfide and particularly boron sulfide have been used with advantage instead of phosphorus pentasulfide to replace carbonyl oxygen by sulfur The addition of sulfur monochloride to olefins followed by reduction of the adduct with sodium sulfide provides a convenient inexpensive route to a large number of episulfides A direct conversion of ar. nitro compounds to isothiocyanates has been reported Sec. phosphines add easily to olefins under UV-irradiation Advances in peptide synthesis include the use of acyloxyphospho-nium salts prepared with hexamethylphosphoramide a simple synthesis with triphenyl phosphite , and the use 4-picolyl esters at the... 

Silicon disulfide is prepared by heating Si in sulfur vapour. Both the structure of this compound (Table 14.6) and the chemistry of SiS2 show no parallels with Si02 SiS2 is instantly hydrolysed (equation 14.76). 

Keywords Matrix-Isolation / Silicon Disulfide / Germanium Disulfide / Raman Spectra... 

In class /, it is possible to distinguish between bridge and spiro structures. Spiro structures occur frequently in inorganic raacromolecules, e.g., in beryllium hydride (p. 4), dimethyl beryllium (p. 41), palladium chloride (p. 46), and silicon disulfide,... 

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