Selenium ligands synthesis

Oxidation reactions were used in the synthesis of porphyrin d, the metal-free ligand system of naturally occurring heme d,. In a total synthesis of porphyrin d,12d oxo functions were introduced into isobacteriochlorin 3 by selenium dioxide oxidation to yield 4. The selenium dioxide selectively attacks the 3- and 8-positions of the partially reduced pyrrole rings of the chromophore. In another synthesis23a c of porphyrin d, an isobacteriochlorin 5, derived by... 

An enormous amount of research has gone into the synthesis and characterization of dmit ligand complexes and related selenium and oxygen isologues. Interest centers on the isolation of... 

The sulfide group forms a large number of complexes where it is in chelation with a different heteroatom. Among the common heteroatoms are N, P and As. These complexes are too numerous to list here, but individual complexes can be found from Table 9 or from refs. 1224 and 1667. It is also possible to synthesize compounds which will form bi-, tri- and tetra-dentate complexes to platinum(II), where sulfur, selenium and tellurium.are the only atoms which coordinate to the metal. A review of complexes formed from ligands of the type RS(CH2) SR has been recently published.1734 This article outlines the synthesis, reactions and spectroscopy of these complexes, and allows the complexes of platinum to be placed in context with those of other transition metals. 

Although the preparations of transition metal complexes with tellurium ligands often involve similar methods to those used for the synthesis of analogous selenium compounds, the ligand chemistry of tellurium has by no means achieved the scope of that now known for selenium. 

Ln E, clusters are air-sensitive, a definite obstacle in composite materials synthesis. Air-stable O-containing ligands (e.g. O2-) could be another solution but the resulting clusters react with water to form hydroxides. Selenium oxide is an alternative soluble source of oxo ligands, giving for instance [Ln8(/u,3-0)2(M5-Se)2(SePh)i6(thf)8]-6thf clusters (fig. 101, bot-... 

The synthesis of optically active selenium-containing reagents as well as their application to stereoselective synthesis is of high current interest. Several products also contain a selenium functionality and their use as chiral ligands and catalysts in asymmetric reaction is promising. Various reactions of this type are known and some recent developments in this novel area are summarized here. 

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