Rhenium-containing heterocycles

Since sulfur is the most effective of all catalyst poisons, the hydrogenation of sulfur containing heterocycles is not easily accomplished unless there are no unshared electron pairs on the sulfur atom or the catalyst used is not affected by the poison. The hydrogenation of the cyelie sulfone, 58, takes palace over an excess of palladium in acetic acid at room temperature and atmospheric pressure (Eqn. 17.57). Thiophene, itself, can be hydrogenated to tetrahydrothiophene over rhenium heptasulfide at 250°C and 300 atmospheres of hydrogen or over a large excess of palladium in methanolic sulfuric acid at room temperature and 3-4 atmospheres. No hydrogenolysis of the carbon-sulfiir bond was observed in these reactions. 

Pseudooctahedral coordination of rhenium(III) centers has also been found for mixed-ligand complexes with tertiary phosphines and A-heterocyclic thiols which coordinate as their neutral thione tautomers. A representative example with thiazoline-2-thiol (HSthiaz) has been characterized structurally. The paramagnetic complex [ReCl3(HSthiaz)2(PPh3)] (235) contains the HSthiaz ligands in trans position. ... 

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