Tellurium complexes heterocyclic

Tellurium, tris(diethyldithiocarbamato)phenyl-stereochemistry, 1, 82 Tellurium complexes acetylacetone, 2, 370 heterocyclic... 

Derivatives of six-member tellurium-containing heterocycles are well represented by the complexes of 10-alkylphenotelluroazines with structure 526 [13,16,112,917 919] ... 

The same method was employed for the synthesis of benzo[<2]phenotellurazine 42 and proven to be more efficient. The heterocycle 42 was obtained in 55% yield (89H1007). A possible explanation for the higher yield of 42 is that the transmetallation reaction in this particular case dominates the side formation of nonreactive complex of the amine with tellurium tetrachloride. There is no need for an additional step of the isomerization of the formed aryltellurim trichloride. 

The ligand chemistry of heterocyclic tellurium compounds has been examined over several years.85 86-92 104-106 The study105 of the monomeric (6) and dimeric (7) complexes, which were obtained from the reaction of Na2PdCl4 and tellurophene and separated by their solubility differences in acetone and chloroform, is illustrative of the preparative chemistry and characterization techniques used in this area of chemistry. 

Current IUPAC and Chemical Abstracts nomenclature has been employed in this index with the former given preference. Substitutive nomenclature has been given preference over radicofunc-tional, additive, subtractive, conjunctive or replacement nomenclature, except where this becomes unwieldy. With many bicyclic and polycyclic compounds bearing heteroatoms, standard bicyclic or polycyclic oxa, aza, and thia replacement nomenclature has often been used. With certain functional groups, where the names are rather complex and probably not familiar to most organic chemists, such as ylides, those compounds have simply been named as sulfur, tellurium and arsonic ylides. Metal catbenes have been treated similarly. With more complex functionality and many heterocycles, the Beilstein Commander Crossfire nomenclature system has been used with certain modifications. 

Thus far only eight different types of five-membered heterocycles with two heteroatoms, one of these being tellurium, are known. Of special interest are those containing S,Se, or Te as the second heteroatom in the ring. Such compounds afford electron-donor components of charge-transfer complexes or radical cation salts, exhibiting properties of the so-called organic metals. 

In CHEC-II(1996), only very few metal complexes involving large ring heterocycles were reported. In the last decade, new information and studies have been conducted on selenium- and tellurium-containing large rings, especially crown ethers capitalizing on their very special features and characteristics. 

There are general reviews on heterocyclic syntheses by cycloaddition reactions of isocyanates and on the use of heterocyclic cations in preparative organic chemistry. More specific topics are 5-hydroxymethylfuran-2-carb-aldehyde, isobenzofurans and related ort/io-quinonoid systems, the conversion of 2//-cyclohepta[Zj] furan-2-one (1) into derivatives of azulene, the synthesis of indoles from o-alkylphenyl isocyanides, and abnormal Fischer indolization reactions of o-methoxyphenylhydrazones. Two reviews on isoindoles have appeared and a lecture on highly conducting charge-transfer complexes that are based on heterocyclic selenium and tellurium donors has been reprinted.Recent advances in the chemistry of imidazole and in the use of nitro-imidazoles as radiosensitizers have been summarized. There have been reviews on benzimidazole A -oxides and on dihydrobenzimidazoles, benzimidazolones, benzimidazolethiones, and related compounds. Other topics are synthetic applications of 1,3-dithiolium and 1,3-oxathiolium salts and of isoxazoles, the chemistry of benzisoxazoles, 2-amino-oxazoles, 5-oxazolones (2), furoxans, benzofuroxans, and related systems, the synthesis of five-membered meso-ionic compounds, and tetrazoles. ... 

Other evidence of the dependence of 5 E) upon the electron withdrawing ability of substituents comes from work on tellurium salts and the species R2TeX2, and the substantial increase in resonance frequency that occurs when R2E forms a metal complex by lone pair donation. " In addition, estimates of charge densities at selenium based on CNDO calculations in IX, X and other heterocycles support this... 

---