Ethanethiolate ligands

The structures and dynamic magnetic behaviours of 31-Dy4 and 31-Tb4 have been presented in Figure 3.22. Four lanthanide ions are aggregated in the grid-like metal core by a central p4-S and eight peripheral i2-S atoms from ethanethiol ligands [38]. The individual lanthanide centres occupy distorted six-coordinate [LnNS5] octahedral coordination environments. Ac susceptibilities measurements reveal pronounced temperature dependence with a series of maxima below 28 K, typical for SMM behaviour, in complex 31-Dy4. Furthermore, an... 

A pentanuclear mixed chalcogen/carbonyl cluster complex with ethanethiolate ligands is the cobalt-containing species [Co5(SEt)5(CO)io], which was structurally characterized by X-ray methods (Fig. 22). 

In the bifunctional radiopharmaceuticals, Tc and Re complexes that are suitable for coupling to antibodies are almost square-pyramidal oxo complexes of tetradentate ligands, as mentioned earlier. Spies et al. [65] recently studied the syntheses and structures of rhenium complexes with a tetradentate NS3 tripod ligand 2, 2,, 2"-nitrilotris(ethanethiol) (l in Fig. 9) as an interesting alternative to the oxo complex. Such ligands could lead to weakly polar, trigonal-bipyramidal complexes in which the metal atom is more strongly shielded than in the square-pyramidal oxo complexes. Schemes for the syntheses... 

Oxovanadium(IV) complexes with SBs derived from Hsal or substituted Hsal and 2-amino-ethanethiol (83) and 3-aminothiophenol (84) were reported by Syamal756-758 and some properties are summarized in Table 40. The corresponding ligands with oxygen atoms instead of sulfur form tridentate complexes with antiferromagnetic properties (see Section 33.5.9.1.iv). 

The chapter by C. J. Swan and D. L. Trimm, which also emphasizes the effect on catalytic activity of the precise form of a metal complex, shows too that, depending on the metal with which it is associated, the same ligand can act either as a catalyst or inhibitor. The model reaction studied was the liquid-phase oxidation of ethanethiol in alkaline solution, catalyzed by various metal complexes. The rate-determining step appears to be the transfer of electrons from the thiyl anion to the metal cation, and it is shown that some kind of coordination between the metal and the thiol must occur as a prerequisite to the electron transfer reaction (8, 9). In systems where thiyl entities replace the original ligands, quantitative yields of disulfide are obtained. Where no such displacement occurs, however, the oxidation rates vary widely for different metal complexes, and the reaction results in the production not only of disulfide but also of overoxidation and hydrolysis products of the disulfide. 

The effects of adding various metal ions and metal complexes on the rate of a model oxidation reaction have been studied in some detail The model reaction chosen—the oxidation of ethanethiol in aqueous alkaline solution in the presence of metal-containing catalysts—involves the transfer of an electron from the thiol anion to the metal The catalytic activity of additives depends upon the solubility of the particular metal complex and varies according to the nature of the ligand attached to the metal ion. In conjunction with different metals, the same ligand can act either as a catalyst or as an inhibitor. The results are discussed in the light of proposed reaction mechanisms. 

For alcohol additions, mono- and dicarbene complexes have been synthesized, for palladium, platinum (487-489), and gold (475, 490- 493), from methanol, ethanol, or ethanethiol (494) additions to the isocyanide precursor. The stability of the gold(I) carbenes can be gauged from reactions with halogens which gave the oxidative addition product without loss of the carbene ligand (492). 

The hydroxylated surfaces are reacted with epichlorohydrin (0.5 M) in solution D, for 4 h at room temperature. The surface is washed sequentially with water, ethanol, and water. Solution E (5 mL) containing each amino-ethanethiol-activated ligand (5 mM) and mercaptoethanol (5 niA/) is hand spotted on the gold surface in predefined linear positions and reacts for 12 h at room temperature, after which the slide is immersed in DMF (50 mL) to remove unbound ligands. 

Dimeric oxo-bridged V111 complexes with bipy or phen as supportive ligands (186) were found to cleave DNA without the addition of exogenous oxidants or reductants.740 The dinuclear V111 complex formed from 2-(dimethylamino)ethanethiol has a linear V—O—V 41 unit (187).793 This compound was the first example of a class of dinuclear complexes containing NS donors.793... 

Tc(lll) Complexes. A novel type of Tc(III) chelate formed by the tripodal chelator 2,2, 2"-nitrilotris(ethanethiol) and a tertiary phosphine or an isocyanide as coligands contains sterically well-shielded oxo-free Tc(III) (Fig. 2.3.6) (Pietzsch et al. 2001 a Seifert et al. 2004 Spies et al. 1999). This moiety fulfils the requirements of a nonpolar building block stable against ligand exchange reactions in vivo. 

Table 20. Effect on the oxidation rates of ethanethiol of several ligands"... 

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