Thioethers metalation

Metal-thioether interactions of biological or medical interest concentrate on complexes of copper. D-Biotin (vitamin H) involves tetrahydrothiophene,44 and the blue copper proteins are believed to contain interactions between different thioether units of methionine (as well as cysteine and histidine)47 (see also ref. 48). 

Strikingly similar results were obtained for all complexes and revealed a structure-function relationship of [M(L)(S )] complexes that can be summarized as follows Metal thioether thiolate complexes exhibit Brpnsted acid-base behavior and can be reversibly protonated. Thiolate protonation drastically influences electron densities at the metal centers and redox potentials of complexes. However, in all these reactions and electronically changing situations, the metal-sulfur core of a specific [M(S )] complex remains invariant. 

The remarkable complexing properties of cyclic thioethers, in particular, those exploited by Schroder s and Yoshida s groups, have stimulated a great interest in metal thioether chemistry. These cyclic ligands bind preferentially to soft metal ions and have allowed the preparation of complexes displaying unusual stereochemistry and/or oxidation states. The most common thioethers involved are [9]ane-S3,... 

Neutral sulfur donors are softer and more polarizable than the neutral oxygen donors of Section 2.7.1.4. Thioethers and sulfoxides are the most common neutral sulfur donors. The trans influence of neutral sulfur donors is greater than that of ethers and is more comparable to that of amines, as based on M-Cl bond lengths. The strength of the metal-thioether bond is usually stronger than that of the metal-amine bond, but weaker than the metal-phosphorus bond. They lie in the spectrochemical series in between chloride and phosphine ligands. 

REDOX-STRUCTURAL CORRELATIONS IN METAL THIOETHER MACROCYCUC COMPLEXES THE STABILISATION OF MONONUCLEAR SILVER(II) and GOLD(n)... 

The work described herein confirms further the ability of polydentate thioether macrocycles to stabilise unusual metal radical centres. This stems from the co-ordinative flexibility of these ligands and the imposition of thioether co-ordination. Thioethers in general are recognised as weak o-donors to metal centres. In the above systems, this is counter-balanced by macrocyclic co-ordination and the potential ability of thioethers to act as either ic-acceptors (via vacant d-orbitals on S, or S-C a -orbitals) or ic-donors (via lone-pair donation). This aspect of covalency in metal-thioether bonding becomes potentially veiy important with soft metal ions of the second and third row transition series. 

Redox-Structural Correlations in Metal Thioether Mactocyclic Complexes The Stabilisation of Mononuclear Silver(ll) and Gold(ll)... 

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