Metal thiolate

Fluorine replacement m perfluorobenzene can be achieved in good yields and high selectivity when heavy metal thiolates are used as nucleophiles [29, 30, 31, 32] (equations 19-21). 

We found recently that the viscosity (//vac) of the colloidal thiolate precursor is a key parameter in controlling the shape of the nanoproducts in the solventless method [8]. Uniform nanowires, rods, or spheres could be made from the corresponding precursors that came from the solutions with different viscosities. The viscosity is a measure of the polymerization of the metal-thiolate complexes. Accordingly, the precursor with the highest viscosity produces nanowires (Fig. 20.5 a), and with decreases in the viscosity, the product morphology changes to rods (Fig. 20.5b) and then spheres (Fig. 20.5c). 

Robbins, A.H. and Stout, C.D. (1992) Metallothioneins Synthesis, Structure and Properhes of Metallothioneins, Phytochelatins, and Metal-Thiolate Complexes (eds M.l. ShDman, C.F. Shawlll and KT. Suzuki), VCH Publishers, Weinheim, pp. 31—54. 

B. Krebs and G. Henkel, Transition metal thiolates — from molecular fragments of sulfidic solids to models of active centers in biomolecules. Angew. Chem. Int. Ed. 30 (1991) 769. 

The aim of this chapter is to review the chemistry of chalcogenolates in the last 10 years. The more recent reviews in this field included chalcogenolates of the s-block elements,13,14 early transition metal thiolates,15 metal complexes with selenolate and tellurolate ligands,16 copper(I), lithium and magnesium thiolates,17 functionalized thiolate complexes,18 19 pentafluorobenzenethiolate platinum group compounds,20 tellurium derivatives,21 luminescent gold compounds,22 and complexes with lanthanide or actinide.23... 

The sulfur analogue of the Wittig rearrangement is an isomerization of a-metalated sulfides to skeletally rearranged metal thiolates, which yield thiols (equation 80). 

Biomimics of noncatalytic, or structural, zinc generally focus on zinc-thiolate clusters designed after the metal—thiolate clusters of metal-lothionein (see Section IV,C). Adamantoid anions of formula [ (jiz-SPh)6(ZnSPh)4] are targets of synthetic and structural study, where each metal ion is coordinated in tetrahedral fashion by bridging and terminal thiolate ligands (see Hencher et al., 1985 Dean and Vittal, 1987, and references cited therein). 

Fig. 39. The three-metal-thiolate cluster in the j8-domain of rat liver metallothionein II (C. D. Stout, personal communication).

Metal thiolates, thiocarbonates and dithiocarbonates are good precursors to prepare sulphides such as CdS and ZnS. A variety of organometallic precursors (usually metal alkyls) have been employed to prepare semiconducting materials (e.g. GaAs, InP). 

Esters of thioarsenious acid, As(SR)3 (R = Me, Et, Pr , Bu", Bu Ph), may be obtained by reacting alkali metal thiolates with arsenic halides (equation 9). In difficult cases (steric hindrance) more vigorous methods are used, e.g. (Bu S)3As (equation 10). 

We have been interested in developing new routes to mesostructured metal sulfides. Our approach capitalizes on well-established solution condensation reactions that can transform discrete, soluble metal thiolate species into solid-state metal sulfide compounds. Here we wish to describe the use of (NH4)2WS4 as a precursor material in the synthesis of three mesostructured tungsten suldifes with the inorganic walls that consist of continuous WS3 chains and WS2. 

Since aromatic amino acids and cysteine are absent, there is no protein absorption above 270 nm. Metallothioneins exhibit a broad absorption peak, with the maximum at 190 mn. Absorptions due to the metal-thiolate complexes show as shoulders at 250 nm (Cd), 220 nm (Zn) and 270 nm (Cu).1458,1459 Theoretical predictions based on the amino acid sequence of the peptide chain indicate that the or-helical conformation is forbidden, and /3-structure is almost impossible to attain. CD and NMR studies on both the metal-containing and metal-free protein confirmed the predictions.1459 1460 However, metallothioneins are stable to tryptic digestion and the slow exchange of many peptide hydrogens of metallothionein with those of the solvent suggest that the protein has a compact and well-defined tertiary structure. 

Several studies on models have been reported, both on the binding of a range of metals to apometallothionein and the design of ligands, particularly with Cys-X-Cys and Cys-X-Y-Cys arrangements as found for metallothionein.1163,1164 All metal derivatives appear to bind in metal-thiolate clusters.1149 Platinum has also been found bound to metallothionein in rat tissues following treatment with cisplatin and the trans isomer.1165... 

Stillman MJ, Shaw CF III, Suzuki KT (1992) Metallothioneins. Synthesis, structure, and properties of metallothioneins, phytochelatins and metal-thiolate complexes. VCH Publishers, New York Stratford IJ, Hoe S, Adams GE, Hardy C, Williamson C (1983) Abnormal radiosensitizing and cytotoxic properties of ortho-substituted nitroimidazoles. Int J Radiat Biol 43 31-43 Stubbe J, Kozarich JW (1987) Mechanisms of bleomycin-induced DNA degradation. Chem Rev 87 1107-1136... 

As mentioned above, reactions of this type have been widely used in the synthesis of macrocyclic ligands. Indeed, some of the earliest examples of templated ligand synthesis involve thiolate alkylations. Many of the most important uses of metal thiolate complexes in these syntheses utilise the reduced nucleophilicity of a co-ordinated thiolate ligand. The lower reactivity results in increased selectivity and more controllable reactions. This is exemplified in the formation of an A -donor ligand by the condensation of biacetyl with the nickel(n) complex of 2-aminoethanethiol (Fig. 5-78). The electrophilic carbonyl reacts specifically with the co-ordinated amine, to give a complex of a new diimine ligand. The beauty of this reaction is that the free ligand cannot be prepared in a metal-free reac-... 

Only irreversible removal of the dithiol or of the solvolysis products can push the equilibrium to the right. Methods of choice are transacetalization to a highly reactive carbonyl derivative, alkylation to sulfide, oxidation of the thiol and formation of metal thiolates, for which mercury(II) salts are frequently used. 

Ligands generally form cr-donor bonds with metal ion sites. Several common ligands in bioinorganic chemistry also have strong re-donor interactions with the metal (thiolates and phenolates, in particular). 

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