Chalcogens oxides

Table 1 Chalcogen oxides and chalcogen oxygen acids investigated by X-ray diffraction... 

Acidic chalcogenates Oxide-chalcogenates Halide-chalcogenates... 

Diorgano chalcogen oxides replaced tellurium in bis[trialkylsilyl] telluriums by oxygen4... 

Of the dozen or more chalcogen oxides which have been reported, only the dioxides and trioxides of sulfur and selenium will be discussed here. Other oxides of sulfur (for example, SO, S2O8, S2O7, and SO4) have been described, but these are unstable and, at present, unimportant. 

As compared to the chemistry of the selenium(IV) and tellurium(IV) halides, knowledge of the reactions and stability of the corresponding halides with divalent chalcogens (oxidation number +2 for the normal dihalides, or +1 for the halides Y-X-X-Y) is less well developed. 

Pnictogen or chalcogen oxides, ethers or amides form O-bonded adducts with both SbCl3 and SbCls. Typical examples that have been characterized include [SbClsL] (L = PyNO, MesNO, (R0)3P0, The structure of [SbClsCDMSO)]... 

In the synthetic area there have been a number of reports dealing with the photodeoxygenation of chalcogen oxides. Thus substituted dibenzothiopenes-S-oxides (62) undergo direct and sensitized photodeoxygenation at a rate which is not simply a function of the size of the substituents. The marked difference in the reactivity of the oxygenated dibenzothiophene dimers (63) and (64) was... 

Several different methods of electrodeposition, such as reduction of (chalcogen) oxide or zero valent (chalcogen) compounds in aqueous electrolytes, deposition from nonaqueous solvents, anodization, deposition from molten salts, and deposition by a multistage process, have been used. Electrodeposition offers a wide range of control of the nanocrystalline film owing... 

Before deposition, the behavior of the copper-indium and chalcogen solutions were investigated separately. The l-V plot of the copper-indium solution showed both deposition and stripping peaks indicating a reversible behavior (Fig. 19). The addition of the triethanolamine decreased the separation of deposition potential between copper and indium to 0.37 volts instead of 0.68 volts. The l-V plots of the chalcogen oxide solutions demonstrated irreversible behavior (Fig. 20). 

Dibismuthines are very sensitive to oxidation. Thus tetramethyldibismuthine fumes ia air, and tetraphenyldibismuthine ia toluene solution rapidly absorbs oxygen. Under controlled conditions, dibismuthines react with chalcogens resulting ia cleavage of the bismuth—bismuth bond and iasertion of a chalcogen atom (105,138,140—142) ... 

Cyclic chalcogen imides in which sulfur is in the formal -f2 oxidation state (or lower) can, in the case of sulfur, act as a source of binary S-N... 

Chalcogen-Nitrogen Compounds with the Chalcogen in Higher Oxidation States... 

The accessibility of the +4 and +6 oxidation states for sulfur and, to a lesser extent, selenium gives rise to both acyclic and cyclic molecules that have no parallels in N-O chemistry. Thus there is an extensive chemistry of chalcogen diimides RN=E=NR (E = S, Se, Te) (Section 10.4). In the case of Te these unsaturated molecules form dimeric structures reflecting the increasing reluctance for the heavier chalcogens to form multiple bonds to nitrogen. The acyclic molecule N=Sp3,... 

The third class of compounds to be discussed in this chapter are those in which an RE group (E = S, Se, Te) is attached to a nitrogen centre. This category includes amines of the type (REfsN and the related radicals [(RE)2N] , as well as organochalcogen(ir) azides, REN3, and nitrenes REN (E = S, Se). Covalent azides of the type RTe(N3)3 and R2Te(N3)2, in which the chalcogen is in the +4 oxidation state, have also been characterized. 

The heavier chalcogens are more prone towards secondary interactions than sulfur. In particular, the chemistry of tellurium has numerous examples of intramolecular coordination in derivatives such as diazenes, Schiff bases, pyridines, amines, and carbonylic compounds. The oxidation state of the chalcogen is also influential sulfur(IV) centres engender stronger interactions than sulfur(II). For example, the thiazocine derivative 15.9 displays a S N distance that is markedly longer than that in the corresponding sulfoxide 15.10 (2.97 A V5. 2.75-2.83 A, respectively). ... 

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