Sulfur rings

Upon solidification of molten sulfur, Stt rapidly changes into S]l, which is converted into SL, although at a much slower rate. The molecular stmcture of Stt is that of an octatomic sulfur chain (1,2). The symbol S]1 designates long, polymerized chains of elemental sulfur. SX is perhaps the most characteristic molecular form of sulfur, namely, that of a crown-shaped, octatomic sulfur ring designated in more recent Hterature as (3). The allotropes have different solubiUty in carbon disulfide. Stt and SX are soluble in carbon disulfide, whereas S]1 does not dissolve in this solvent. 

Sulfur crystallizes in at least two distinct systems the rhombic and the monoclinic forms. Rhombic sulfur, Sa, is stable at atmospheric pressures up to 95.5°C, at which transition to monoclinic sulfur, SP, takes place. Monoclinic sulfur is then stable up to its natural melting point of 114.5°C. The basic molecular unit of both of these crystalline forms of sulfur is the octatomic sulfur ring Other forms of sohd sulfur include hexatomic sulfur as well as... 

Constants and Chemical Properties. The constants of sulfur are presented in Table 1. Two freezing points ate given for each of the two crystalline modifications. When the Hquid phase consists solely of octatomic sulfur rings, the temperature ranges at which the various modifications form are called the ideal freezing points. The temperatures at which the crystalline forms are in equiHbtium with Hquid sulfur containing equiHbtium amounts of... 

Mixture of soluble sulfur rings other than Sg Soo Polymeric sulfur dissolved in liquid sulfur (mixture of very large... 

A number of lower sulfur oxides have been described. Most of these oxides are derived from cyclic sulfur polymorphs and were usually prepared by oxidation of these molecules by organic peroxo acids. The oxides have the general formula SraO and n may vary from 5 to 10. For n = 7 even the dioxide S702 is known.4 Not all of these phases were characterized by X-ray diffraction, but the molecular structures are certain with respect to vibrational spectroscopy. The oxygen atom is in exo position with respect to the sulfur ring as it has been shown by X-ray diffraction for SgO and S70, respectively (Figure 2).5,6... 

It should also be noted that polysulfido complexes are not only interesting because of their structures and reactivity, but also because of their possible applications. They can, for example, be used to prepare sulfur rings of predetermined size and they are also suspected to play a role in catalysis (particularly in hydrodesulfurization). 

Conformations of Most Common Metal- Sulfur Rings... 

Compared with the large number of nitrosyl complexes, only a few examples of thionitrosyl complexes have been studied. Although NS does not exist, a number of synthetic approaches to thionitrosyl complexes have been reported the reaction of nitrido complexes with S2CI2 or TMSNCS, treatment of chloro or 0x0 complexes with trithiazyl chloride or S(NTMS)2, or the use of heterocyclic nitrogen-sulfur rings. Pre-formed thionitrosyl cations in [NS][SbF6] or [NS)[AsFg] have been used to prepare the cationic complex [Re(NS)(CO)5] " in liquid S02. ... 

In their quest for new methods for preparing new sulfur rings 94), Wilhelm and Schmidt 125) studied the simultaneous addition of sulfane and chlorosulfane to cold dry ether,... 

Schmidt 90) succeeded in 1968 in preparing S7, the first sulfur ring with an odd number of atoms. The synthetic path employed for preparing Sg and S12 does not provide high yields, thus a new method had to be found. The reaction... 

By using the S3mthetic method of Feher modified by 8chmidt and Wilhelm, Steudel and Rentsch (106) prepared a sulfur ring 8gO (Fig. 8b) by the reaction ... 

The 8gO is stable if stored at low temperature. This molecule contains an oxygen attached to the normal cyclooctasulfur molecule. The branching of the sulfur ring is quite surprising. The presence of the oxygen, as... 

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