Mono complexes rhenium

Rhenium forms a number of mono-oxo, CTs-dioxo, and trans-dioxo complexes in oxidation states IV through VII. Reversible, proton-independent, one-electron potentials for several systems are represented in Table 1 [13-22, 35, 36]. As is the case forTc, a large change in E° for a given redox step can be produced by changing the ancillary ligands. 

Re(CO)3(MeCN)3]PF6 has been prepared and this compound appears to be a useful precursor for the preparation of cationic rhenium carbonyl compounds.625 Carbonylation of tertiary phosphino-complexes under reducing conditions provides a convenient synthetic route to rhenium mono- and poly-carbonyl complexes.626... 

Catalytic oxidation of 239 to the quinone 240 was also effected with H2O2 catalyzed by methyltrioxorhenium(VII) (McRcOb) (Scheme 60)", where a small amount of hydroxy-substituted quinone 280 was produced in addition to 240 (70%). In this reaction, MeRe03 is stepwise converted by H2O2 into the mono- and bis(peroxo)rhenium complex MeRe(02)20-H20 (281). This active oxidant then reacts with the phenol to give the epoxide 282, which is further converted to the two quinones (240 and 280). 

Another system based on rhenium and thiophosphine ligand is also capable of reversely binding alkene moieties (Scheme 15) [42]. After electrochemical oxidation of complex 49, the ethylene is bound by the sulfur atoms of the ligand. As in complex 47, the olefin has a stronger affinity for the oxidized form 49 (i.e., 49+ and 49 +) than for the reduced complex (Kj > Kj> Kj). In the neutral species (non-oxidized forms) the equilibrium is in favor of 49 over 50 even in a large excess of ethylene. In the case of the two-electron oxidized species, the equilibrium is in full favor of 50 +, with no spectroscopic evidence of the presence of 49 +.Whenever complexes are one-electron oxidized both mono-cationic forms (49+ and 50+) are present, the ratio depending on the applied pressure of ethylene. 

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