Tetra valent sulfur

This is the name give by Chemical Abstracts to compounds with tetra-valent sulfur (65), but the nomenclature is confusing as the term sulfodii-mide is also applied to the hexavalent compounds (66). The former compounds (65) have been reviewed by Kresze,88 and are briefly discussed below the latter compounds (66) have been discussed by Haake89 and are dealt with in Section VI,D. 

The chemistry of the oxide chlorides, bromides, and iodides of tetra-valent tellurium is in marked contrast to the more variable chemistry of corresponding more acidic sulfur and selenium compounds. One of the reasons seems to be the reluctance of Te(lV) to form stable Te=0 double bonds in condensed systems. In contrast to the numerous oxo-haloselenatesdV) with strong Se=0 bonding, or to compounds such as SOCI2, SO2CI2, SOaCl and their homologues, no comparable Te ana-... 

Let s now consider whether the representation chosen—the traditional one with multiple bonds versus the newer one—affects the valence of the central atom. Let us do so with a couple of examples involving higher-valent sulfur, say, SOCI2 and SO2CI2. If we consider the traditional structural formulas with double bonds, the S is clearly tetra- and hexa-valent in the two molecules, respectively. Simply count the electrons, denoted by blue dots, that the sulfur has used to form bonds. 

Sulfur can exist in formally tetra- and hexa-valent forms, and this was extended in the past to the postulate that it should be possible to generate a six-membered sulfur-containing ring with overall neutral charge and a tetravalent heteroatom that would be fully the equal of benzene for stability and chemical reactivity. Indeed these systems were trivially known... 

The tetra- and hexa-valent states are significantly more stable for selenium and tellurium than they are for sulfur. Thus, whereas SCI4 is exceedingly unstable, decomposing above -30 °C, SeCl4 and TeC are stable under ordinary conditions. With chloride ion acceptors, both tetrachlorides form [ChCl3]+ (Ch = Se, Te) cations ... 

---