Chalcogeno compounds

Table 4. Oxidation potentials (peak potentials, Ep) of fluoroalkyl chalcogeno compounds ...

The oxidation potentials of various fluoroalkyi sulfides, selenides, and tellurides have been determined by use of cyclic voltammetry. These substances exhibit irreversible multiple anodic waves. In Table 5 is summarized the first oxidation peak potentials ( p) of these substances together with those of some nonfluorinated and other electronegatively substituted chalcogeno compounds. In all cases, the fluorinated compounds are oxidized at more positive potentials than the corresponding nonfluorinated compounds because of the electron-withdrawing effects of fluoroalkyi groups. It should be noted... 

Table 5. Oxidation Potentials (Peak Potentials, fp) of Fluoroalkyl Chalcogeno Compounds ...

Allylsilanes are known to be more easily oxidized than the corresponding unsilylated olefins. However, introduction of a fluoroalkyl group to the 2-position of an allylsilane causes a large increase in its oxidation potential as shown in Table 7. This effect is quite different from those observed with fluorinated chalcogeno compounds and amines (Tables 5 and 6). 

As described above, studies of anodic partial fluorination have focused on aromatic, benzylic and olefmic compounds. However, there have as yet been no reports on anodic partial fluorination reactions of chalcogeno compounds. 

Several organoselenium and tellurium compounds having a chiral ferrocenyl-chalcogeno moiety 11-19 were also prepared as shown in Scheme 2. 

The chalcogeno esters (E = S, Se, Te) presented in Scheme 5-31 are yellow to red-brown compounds that are air-stable in the solid state [89] the benzoic acid derivatives Fc-S-C(0)Ph [82] and fc(E-C(0)Ph)2 (E = S, Se) [91] had been described earlier. The orange derivatives of the ferrocenyl carboxylic acid contain two or three metallocene units connected by ester links (Fig. 5-12). The corresponding esters of the alcohols Fc-OH and fc(OH)2 (E = O) can be obtained [73] by direct ferrocenoylation using Fc-C(0)Cl. 

Compounds such as E(SiMe3)2 and RESiMca (E = S, Se, Te) react readily with transition and main group metal salts to form metal chalcogenide or chalcogeno-late bonds (Eq. (2)-(4)). 

We decided to attempt the synthesis of dimethyl-TTT (DMTTT), Fig. 1, and related chalcogeno derivatives. The methyl group was selected as the substituentr because it was expected to impart improved solubility to the parent compound, because of its size, and because it was expected to enhance the electron-donating ability of DMTTT relative to TTT. The two methyl groups were placed such that the symmetry of the donor... 

The series of di-chalcogeno imidodiphosphinate ligands can be represented by the general formula (9.686a). Most commonly R has been Ph or Pr in synthesised varieties to date. Typical tellurium compounds are (9.686b) and (9.686c) with E = Te. Another recently made complex is (9.686d) [33,34]. 

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