Chalcogens molecular structures

The nature of multiple bonding between germanium and the heavier chalcogens in the complexes (/74-Megtaa)GeE (E = Se, Te) is best described as an intermediate between the Ge+— E and Ge=E resonance structures. The preparation of these complexes involves the addition of the elemental chalcogen to (/74-Mestaa)Ge, which is synthesized by the metathesis of GeCl2(l,4-dioxane) and Li2[Mestaa] (Mestaa = octamethyldibenzotetraaza[14]annulene dianion). The molecular structures of both complexes are shown in Figures 5 and 610. 

A breakdown of the structural results by type of surface shows results for nearly 50 clean, unreconstructed metal surfaces and about 10 alloys and reconstructed metal surfaces. The structures of about 65 atomic overlayers on metal surfaces have been determined, some 40 of these involving chalcogen atoms. Just over 20 molecular structures have been determined for metal surfaces, half of these being overlayers of undissociated carbon monoxide and the others various hydrocarbons. Turning to semiconductors, some 13 clean, usually reconstructed structures were determined, against nearly 10 atomic overlayer structures. In addition, about 15 insulator surface structures have been investigated. 

Significant progress has been reported in the last years on all the known chalcogen(IV) halides in their structure and bonding they all are related to the three prototype molecular structures referred to above. Results in detail are reviewed here. 

Fig. 25. Molecular structures of anionic halo-alkoxo-chalcogenates(IV), with bond distances (A) (a) the tetrachloromethoxoselenate(IV) ion in [(C6H5)4P+][SeCl40CHs ] (b) the trichloro(dioxo-ethylene-0,0 )tellurate(IV) ion in [(C6H6)4P+][TeCl3(0C2H40) ]...

As mentioned in Section 1, similar to BEDT-TTF, M(dmit)2 molecules are members of a family of multi-chalcogen % molecules. The concepts of the molecular design used in the development of the organic metals are also valid for the M(dmit)2 conductors. Owing to the resemblance in the molecular structures, M(dmit)2 molecules tend to form two-dimensional S S networks in the crystalline state similar to those of BEDT-TTFs. In the case of the M(dmit)2 complex containing peripheral chalcogen n donor molecules, such as TTF, even three-dimensional S S networks can be formed [18]. 

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