Rhenium complexes sulfur ligands

Rhenium complex (46) is also known to add H2 and N2 <81CC451> to the metal center. Ruthenium complex (47) and osmium complex (48) add sulfur to give complexes with unusual S6 2 ligands <84AG(E)814>. 

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. 

Reported rhenium complexes possess one [70-74], two [75], and three [75] dithiocarboxylato ligands coordinated to the one rhenium atom to form a high coordination state, as in the case of the technetium complex [76]. One of these complexes 29 is synthesized from Re(VII)S4 and (PhCSS)2 (Fig. 10) [72]. An internal redox reaction occurs and Re( VII) is reduced to Re(III) in the synthetic process. Addition of sulfur-abstracting reagents, Ph3P or Et4NCN, produces the heptacoordinate complex 30 with the neutral capped octahedron structure or... 

Cp(CO)2Re(THF) forms the complex 105 upon reaction with thiophene (89JA8753, 910M2436). Similar species are known for 2- and 3-methyl-, 2,5-dimethyl, and tetramethylthiophene (91IC1417). Thiophene in 105 is S-coordi-nated, and the sulfur atom is pyramidal. Treatment of 105 with Fc2(CO)9 produces 106, where the thiophene ligand is bridge-coordinated via the sulfur atom to rhenium and four carbon atoms of the dienic system with iron (the coordination mode). The pyramidal nature of the sulfur atom is preserved. The -coordination of thiophene separates the dienic and sulfur counterparts of the ligand and decreases the TT-electron delocalization, which leads to the enhanced basicity of the sulfur atom. 

Rhenium(III) complexes with sulfur dioxide ligands have been obtained by oxidation of dimeric sulfido-bridged complexes either by air or by NO(PFe). The oxidation of the bridging sulfur atoms is facilitated by the high electron density at these ligands. 

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