Sulfur-rich zinc complexes

Zinc is the active metal in the largest group of metalloproteins found in the nature. Recently a new class of zinc enzymes with a sulfur-rich environment has emerged the thiolate-alkylating enzimes, the most prominent of which is the cobalamine-independent methionine synthase.126 For these reasons several monothiolate zinc complexes have been prepared for the modelling of these enzymes with different N2S as (13),127 130 N20,13° 132 N3,132,133 S3,134 tripod ligands, or with Cd because of the favourable spectroscopic properties with an S3 tripod ligand.135... 

Thioneins are apoproteins that are exceptionally sulfur-rich (composed of greater 30 mol% cysteine). These proteins are found in high abundance in liver and kidney cytoplasm where they form metallothioneins (the holo-protein forms) upon complexation with metal ions. Thi-onein synthesis is induced by the presence of metals, especially zinc, copper, mercury, and cadmium. 

It has been suggested that the use of zinc dithiolate complexes as vulcanization catalysts may be closely related to the ability of these complexes to form sulfur-rich complexes that have very labile disulfide sulfur atoms (230). 

More recently, the hexasulfido zinc complex [(TMEDA)Zn][S6] has been used to prepare extremely sulfur-rich cyclic polysulfanes by reaction with 1,2-benzene-bis(sulfenyl chloride). ... 

Reedijk and co-workers (2004) used the combined approach of density functional calculations and the matrix-assisted laser-desorption ionization (MALDI) MS approach in order to probe this important first step. The calculations suggested that the hypothetical sulfur-rich trithiocarbamate complex 507 was only some 59 kJ moP higher in energy than trithiolate-zinc... 

---