Sulphur ligand

Thiols and other sulphur ligands can be used to reduce Au3+ to Au+ but gold(III) complexes can be made, for example, with tetramethylthiourea (tmu),... 

Reactions involving metal complexes of sulphur ligands. L. F. Lindov, Coord. Chem. Rev.. 1969,4, 41-71 (223). 

Infrared of rj5-C5H5Mn(CO)2S, S = sulphur ligand demonstrate Mn-S conformational isomerism. Isotopic data are included... 

The first suggestion that the EPR signals could be due to heme iron associated with sulphur ligands is due to Mason (37, 38), basing his conclusions on the general chemistry of the system (4). In a very different set of complexes Roder and Bayer (39) observed that cysteine and its derivatives will interact with a high-spin iron(III) trisethanolamine complex to give a set of EPR g-values not too different from those of P-450 and they too were led toward the conclusion that iron and sulphur were associated in P-450. 

Table 5. EPR g values of metmyoglobin (Mb) and met-hemoglobin (Hb) complexes with sulphur ligands (43)...

Vanadium-sulphur ligand complexes have been studied as models of biological vanadium systems (see Vol. 5, p. 42). Tris(diethyldithiocarbamato)vanadium(iii) is more easily reduced and oxidized than its 8-hydroxyquinolinato analogue. It is suggested that this is a reflection of the increased electron density and/or electron mobility in the sulphur ligand. 

Comparative studies of rates and mechanisms for square-planar nickel(ii), palladium(ii), and platinum(ii) complexes containing bidentate sulphur ligands, which were discussed in the previous volume of this Report, have continued. 

The more typical iron-sulphur centre contains two iron atoms, two sulphides and four cysteine sulphurs . It is believed that each iron is surrounded by four sulphur ligands in an approximate tetrahedral array. Every iron is coordinated by two sulphurs from cysteine and two from sulphide, with each of the sulphides binding both irons. The general structure of the two-iron redox centre is depicted below. 

An intense eifort by physicists, physical chemists, biochemists, inorganic chemists and X-ray crystallographers has now defined the common attribute of the nonhaem iron proteins. It is an iron centre tetrahedrally coordinated by four sulphur ligands. A number of variations within this theme are recognized. The simplest case is found to be rubredoxin from Clostridium pasteurianum, a 6000 molecular weight protein whose exact electron transport function is unknown. 

---