S, Se, and Te cations

The 8-ring cations in S8(AsF6)j and Se8(AlCl4)2 have very similar shapes (Fig. 16.1(b)), intermediate between the crown shape of Sg and that of S4N4  

These rings differ from the crown ring of Sg in having one very short distance across the centre of the ring and two others which are also much shorter than would correspond to van der Waals contacts  

It would appear that as electrons are removed from Sg (48 valence electrons) bonds are formed across the ring the 44-electron isoelectronic S4N4 ring is shown since is formed in preference to Sg . In Sg the S-S bond length is apparently similar (2-04 A) to that in Sg the bond angles range from 92 to 104° (compare 

Bond angles C-S-C close to 100° are found in cyclic molecules based on strain-free 6-rings. All those studied have the chair conformation examples include l,4-dithiane/ 1,3,5-trithiane, and hexathia-adamantane. The last compound, S6(CH)4, is structurally similar to (CH2)eN4 and (CH2)6(CH)4. Trithiane forms many metal complexes the structure of S3(CH2)3. AgC104. H2O is mentioned in Chapter 3 (p. 90). 

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