Chalcogens 671 cations

Chalcogen-nitrogen cations can be generated by the reactions of homopolyatomic chalcogen cations with azides. For example, the... 

Simple cations are unknown within Group 16 (besides Po), but several highly colored polyatomic cations (cationic clusters), like S " ", Sg, Se, SCg, Te, and Teg" ", have been isolated in non-aqueous media [15]. Some mixed chalcogen cationic clusters have also been reported. These are all unstable in water. 

The number of known polycationic compounds of main group elements is far less than that of polyanionic compounds. Examples include the chalcogen cations S]+, S]+, Se]o and Teg that are obtained when the elements react with Lewis acids under oxidizing conditions. The ions S]1, Sc]1 and Te] have a square structure that can be assumed to have a 6n electron system. 

Mixed group 15 group 16 polycations are rare and tend to form clusters. For example, the arsenic-chalcogen cations [As3E4]" (E = S, Se) have polycyclic structures similar to those of the well-known isovalent species P4S3 and the bismuth-tellurium cation [Bi4Te4]" " adopts a slightly distorted cubic... 

Tellurium forms the most extensive series of homoatomic chalcogen cations. The list of structurally characterised tellurium polycations includes Te4, 6, Te6, Teg and Teg and also the polymeric species (Te4 ) ,... 

Several approaches have been used for the synthesis of heteroatomic chalcogen cations, including (a) direct oxidation of a mixture of two chalcogens with oleum, MF5 (M = As, Sb) or transition metal halides, (b) reaction of a chalcogen with a homoatomic cation of another chalcogen and (c) compro-portionation of the homoatomic cations of two different chalcogens. 

The number of known polycationic compounds of main group elements is far less than that of polyanionic compounds. Examples include the chalcogen cations S4 , S , Se" ... 

As early as 1804 solutions of non-metals such as sulfur and iodine in oleums were reported to produce highly colored solutions but the nature of the solutes was unknown. From the mid 1960s, Gillespie s group adduced reliable evidence to indicate that solutions such as these and others in HS03F and HF contained the polyatomic halogen cations It, if", IJ, If, Brf and Brf and the chalcogen cations listed in Table 2. 

Fig. 8. Sensitizing dyes of the cyanine class. K. = N — alkyl or chalcogens (O, S, Se, Te) R = chloro, phenyl, or additional benzene ring R = methyl, ethyl, or hydrogen n = 0, 1, 2 and RPRIME, R " = alkyl or sulfoalkyl. Solubihty in methanol for a carbocyanine dye n = 1 X = S R = Cl R = ethyl. Cationic dye (R" = R " = ethyl anion = bromide) 9.5 mmol/T. neutral dye (R" = ethyl R " = sulfopropyl) 3.6 mmol/L anionic dye (R" = R = sulfopropyl ...

By long tradition, a group of cationic pyran derivatives have trivial names, i.e. (186)-(189), which are retained by lUPAC. These names may be modified by the prefixes thio-, seleno-and telluro- for their chalcogen analogs. 

Electrochemical methods may also be used in the synthesis of chalcogen-nitrogen compounds. For example, the electrochemical reduction of salts of the [SsNs]" cation (Section 5.3.9) in SO2 or CH2CI2 at low temperatures produces microcrystals of the superconducting polymer (SN). ... 

In general, spinel and other chalcogen-based thiospinels with Z=8 leads to the total unit cell content of 8 and 16 (8 a and 16 d sites) cations and 32 anions in the 32 e site corresponding to the formula A8B15O32. In spinels, the AX4 tet-rahedra share comers with BXg octahedra and the octahedra are Hnked together by sharing edges (Fig. 15.1). 

Equilibria considerations on solution-grown zinc chalcogenide compounds have been put forward by Chaparro [28] who examined the chemical and electrochemical reactivity of solutions appropriate for deposition of ZnS, ZnSe, ZnTe (and the oxide ZnO) in order to explain the results of recipes normally used for the growth of such thin films. The author compared different reaction possibilities and analyzed the composition of solutions containing zinc cations, ammonia, hydrazine, chalcogen anions, and dissolved oxygen, at 25 °C, by means of thermodynamic diagrams, applicable for concentrations usually employed in most studies. 

As described previously, the two dimethyl amino methyl groups on the 2,6-position of the phenyl ring of teluride 161 act as internal ligands (Koten s arms) and stabilize the cation generated at the central Te atom (see Equation 44). Furukawa and co-workers subsequently showed that these Koten s arms also activate the molecule to release alkyl substituents which are attached to the central chalcogen atom <1995JA10153> and <1997BCJ2571>. For example,... 

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