Rhenium 380 Subject

Potassium perrhenate (KRe04) is reduced by hydrogen in two stages. The first operation is carried out at 500 to 550 °C. The reduced product is washed to remove the hydroxide. The powder is then subjected to a second reduction at a higher temperature (900 to 1000 °C). The product is washed, first with dilute hydrochloric acid and then with water, and dried in vacuum or in a current of hydrogen. Solid rhenium is made by powder metallurgy techniques. 

Mol, Visser, and Boelhouwer 741 subjected 1,2-dimethyl-butane (ring structure of the suggested transition state for disproportionation of propylene) to rhenium oxide-alumina catalyst under conditions which propylene gives high disproportionation conversions. This compound was stable only at high temperatures (730 °C), where thermal cracking occurred, were olefins found. 

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]. 

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... 

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