Thiolates metal complexes

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,early transition metal thiolates,metal complexes with selenolate and tellurolate ligands, copper(I), lithium and magnesium thiolates,functionalized thiolate complexes,pentafluorobenzenethiolate platinum group compounds, tellurium derivatives, luminescent gold compounds, and complexes with lanthanide or actinide. ... 

Some thiolate metal complexes, unlike the oxygen complexes referred to above are powerful antioxidants (see Chapter 1) and undergo inversion to prooxidant metal ions in sunlight. The iron, manganese, cobalt, vanadium and cerium dithiocarbamates (II) are typical examples of such restrained prooxidants. 

Another example of highly effective melt stabilizers are the thiolate metal complexes (e.g. MDRC, MDRP, MRX, M = Ni, Zn) which are also thermal and UV stabilizers for polyalkenes (see Section 19.3.3.1.V, 19.4.2.2.i and 19.4.2.2.ii) and no hydroperoxides can be detected in polymers containing them after processing. In addition to their peroxidolytic function dithiolates have the ability to trap alkyl peroxyl radicals The contribution of this trapping mechanism to... 

Thiohvdrates metal complexes, 2, 516 Thiohydroxamic acid meta complexes, 2, 806 Thiolates... 

Thiolates as Ligands in Transition Metal Complexes (J. R. Dilworth)... 

Cf produces two fission products that travel in opposite directions. If one projectile hits the sample, ions will be produced. These ions may then be focused and measured by TOF MS. The other projectile may be used to measure the start of the ionization process. This method has been used to study the ions produced from the ionization of metal complexes such as cadmium thiolates (33) and lanthanide phthalocyanine complexes (34). This method has also been used on metal oxides such as La203 to produce metal oxide cluster ions (35). 

As mentioned earlier, the bulky terphenyl thiolate ligand -SC6H3-2,6-Mes2 has been shown to stabilize nominal two-coordination in transition metal complexes.53,54 Figure 30 represents the X-ray crystal structure of the iron derivative, Fe(SC6H3-2,6-Mes2)2.53... 

Transition metal complexes of sterically hindered thiolate ligands have been reviewed. " These ligands give rise to unusual geometries and oxidation states, and low coordination numbers in their complexes. 

The best enantioselectivity (35% ee) was observed in the reaction of l-(l-naphthyl)-2-propyn-l-ol with acetone in the presence of a complex bearing a 1-naphthylethylthio-lato moiety as a chiral ligand. Although the enantioselectivity is not yet satisfactory, this was the first example of an enantioselective propargylic substitution reaction catalyzed by transition metal complexes [27]. It is noteworthy that the chiral thiolate-bridged ligands work to control the chiral environment around the diruthenium site. 

Simple a-diimines are hydrolytically unstable, but can be stabilized as metal complexes by virtue of the formation of stable five-membered chelate rings.68 69 a-Diketones and glyoxal undergo metal template reactions with amines to yield complexes of multidentate ligands such as (34),70 (35)71 and (36).72>73 In the last case, the metal exerts its stabilizing influence on the a-diimine partner in an equilibrium process (Scheme 5). The same phenomenon occurs with amino alcohols74 75 in addition to amino thiols. The thiolate complexes (37) can be converted to macrocyclic complexes by alkylation in a kinetic template reaction (Scheme 5).76 77... 

One of the simplest and widely used methods of forming C-S bonds involves nucleophilic attack of a thiolate on a suitable C-centred electrophile such as an alkyl halide (Fig. 5-74). Co-ordinated thiolate ligands behave as nucleophiles in exactly the same manner, and the method has been extensively used for the preparation of thioethers and their metal complexes. The method has been particularly commonly utilised in the formation of macrocyclic ligands in templated syntheses (see Chapter 6). 

All of these reactions are, in principle, reversible, and many examples are known where thiolate complexes may be prepared by the reaction of disulfides with low oxidation state metal complexes. 

With establishment of the crystal structure, three major features concerning the electronic structure of the blue copper site can be addressed. These features are 1) the nature of the thiolate and thioether bonds, 2) the nature of the ground state wavefunction and 3) the extent of covalency. We have also become strongly involved in using photoelectron spectroscopy as a powerful approach toward determining covalency in transition metal complexes. These will be discussed in turn. 

The formation of complexes of l,2,3,4-thiatriazole-5-thiol has been well described in CHEC-II(1996) 1,2,3,4-thiatriazole-5-thiol can form complexes with various metals such as palladium, nickel, platinum, cobalt, zinc, etc. <1996CHEC-II(4)691>. These complexes can be prepared either by cycloaddition reactions of carbon disulfide with metal complexes of azide anion (Equation 20) or directly from the sodium salt of l,2,3,4-thiatriazole-5-thiol with metal salts. For instance, the palladium-thiatriazole complex 179 can be obtained as shown in Equation (20) or it may be formed from palladium(ll) nitrate, triphenylphosphine, and sodium thiatriazolate-5-thiolate. It should be noted that complexes of azide ion react with carbon disulfide much faster than sodium azide itself. 

Final purification by use of metal complexes was also applied in the syntheses of the ligands XS4—H4. These ligands exclusively contain thiolate donors and were prepared by Hahn et al. (23) using 2,3-dimercaptobenzoic acid as starting material (Scheme 8). Isopropyl or benzyl protection of the thiol functions, conversion into the acyl chlorides, reaction with a,oo-diamines, and deprotection of the sulfur atoms enabled the connection of two 1,2-benzene-dithiol units via carboxylic acid amide bonds. 

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