Subject Rhenium complexes

Rhenium displays an unusual array of oxidation states and coordination numbers that make it the subject of much current research. The following preparation, adapted from one developed by Chatt and coworkers, provides a convenient synthesis of trichlorooxobis(triphenylphosphine)rhenium(V)1 based on either rhenium(VII) oxide or perrhenate salts. The trichlorooxo compound is a versatile intermediate for the synthesis of other rhenium complexes such as wer-trichlorotris(dimethylphenylphosphine)rhenium-(III),2 as described below. The rhenium(III) complex, in turn, provides a starting point for synthesis of other compounds such as frans-tetrachloro-bis(dimethylphenylphosphine)rhenium(IV)3 and tris(dimethylphenylphos-phinepentahydrido)rhenium(V).4 An alternative synthesis of the trichloro-complex is described in the accompanying preparation by Douglas and Shaw.4... 

Herrmann and co-workers showed that the 17-electron complex 62 may be subjected to electrochemical oxidation as well as reduction (54.55). The redox potentials of the respective halo complexes follow the expected trend for change in the halide ligands. In accordance with these electrochemical studies, both chemical oxidation and reduction reactions of 62 were found [Eqs. (49) and (50)]. Oxidation of the rhenium complex Re(CCMe3)(// -C5Me5)Cl2 by dioxygen results in cleavage of the neopentylidyne ligand from the metal center as pivalic anhydride and pivaloyl chloride. 

Larger rhenium complexes are also the subject of a number of publications. Reaction of an excess of thietane with the thietane complex fRe3(CX))jQ(p-H)3(p-cyclo-SCH2CH2CH2)] affords a number of ring-opening oligomerisation products from which sulfur containing macrocycles such as 12-S-4, 16-S-4 and 24-S-6 can be eliminated upon addition of pyridine . Addition of... 

A number of basic studies toward the application of carbohydrates as ligands for the [M(CO)3]+ entity have been described. Kliifers et al. demonstrated the ability of the hydroxy groups in a variety of carbohydrates to bind in different, pH and stoichiometry dependent ways to rhenium. A variety of complexes were structurally characterized [77]. Finally, two 1-thioglucose entities have been coupled to a central 4,4 -bipyridine ligand. These unique conjugates could be labeled at high dilution, exhibited perfect in vitro stability but were not yet subjected to biological studies [78]. 

Introduction.—The organometallic chemistry of technetium and rhenium reported during 1974 has been surveyed. The ligand-induced redox reactions of rhenium halides have been reviewed, and the chemistry of cyanide complexes of Group Vila metals has received attention. The electrochemistry of technetium and rhenium has been the subject of two reviews, and a general monograph on the production, uses, and disposal of technetium has appeared. Recently published crystal structures of complexes of technetium and rhenium have been collated. ... 

In the previous chapter (07AHC(93)185), complexes of polypyridine ligands with non-transition and early transition metals were considered. Most publications, however, are dedicated to the rhenium(I) and ruthenium(II) complexes, and the number of sources is so high that they deserve separate chapters. Moreover, studies of such complexes become more and more popular due to their unique photochemical and electrochemical properties and ability to form molecular assemblies and nanocrystallites. Herein we consider organomanganese and organorhenium complexes of polypyridine ligands. As always in this series of chapters, emphasis will be on the synthetic and coordination aspects, as well as reactivity. We have attempted to document all the publications on applied aspects, but without analyzing them since this could be the subject of a separate chapter. 

In further applications, dithienylethene compounds have been tethered to P-cyclodextrin for photocontrolled uptake and release of a porphyrin <04CEJ1114>, whereas a cationic dithienylethene derivative has been subjected to electrochemical reductive cyclization <04AG(E)2812>. A dithienylethene containing a 1,10-phenanthroline unit and a rhenium(I) complex thereof has also been prepared and studied <04JA12734>. 

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