Vanadium complexes thioethers

Since the oxidative polymerization of diphenyl disulfide catalyzed by VO(acac)2 results in selective formation of thioether bonds without any oxygenated compounds such as sulfoxides and/or sulfones, it should be noted that H20 should be produced predominantly by the reduction of 02 catalyzed by the vanadium complex without the formation of partially reduced side products such as H202. 

In 1995, Bolm et al. reported that the vanadium complexes of the triden-tate and amino-acid derived ligands 15 catalyze the enantioselective sulfoxidation of prochiral thioethers with dihydrogen peroxide as the terminal oxidant (Scheme 8) (24). The ligands are synthesized by a one-step condensation of the readily available salicylic aldehydes 16 with amino-acid derived amino alcohols, such as 17a. 

The most active d metal peroxo complexes toward nucleophilic substrates, like amines, phosphines, thioethers, double bonds etc., are molybdenum, tungsten and rhenium derivatives vanadium and titanium catalysis is also important, in particular when... 

Vanadium trichloride or tribromide reacts with thioethers giving [VX3L2] (X = C1 or Br L = SMe2, tetrahydrothiophene or SEt2).288,289 The complex with di-n-propyl sulfide could not be isolated.288 These compounds are oxidized very easily. Solubility, molecular weights and conductance show that they are monomeric and non-ionic. Dipole moments, IR and electronic spectra are consistent with trans trigonal bipyramidal structures. 

Vanadium trichloride or tribromide reacts with thioethers giving [VX3L2] (X = Cl or Br L = SMe2, tetrahydrothiophene or The complex with di-/i-propyl sulfide could not... 

The reactions between TiCl., TiBr., TiCl, VCl, VCl, and VBr with a range of monodentate sulphur ligands, have been investigated. The ligands used include the aliphatic thioethers, R S, for R =Me, Et, Pr, and Bu, and tetrahydrothiophen and pentamethylenesulphide. Notable differences have been observed in the reactions of the halides of the two elements. Thus, whereas the tetrahalides of titanium form simple adducts with all ligands tried, vanadium(IV) chloride is reduced rapidly and quantitatively to the tervalent state. Furthermore, tervalent vanadium forms a series of well-defined complexes with sulphur ligands, but the complexes formed by tervalent... 

Biomimetic Cu(II) and Fe(II) complexes with bis- and tris-pyridyl amino and imino thioether ligands and vacant (or potentially so) coordination positions (Fig. y are active as catalyst precursors for the solvent- and halogen-free MW-assisted oxidation of 1-phenylethanol by TBHP, in the presence of pyridazine or other N-based additives. Maximum TOF of 5220 h (corresponding to 87% yield) was achieved just after 5 min of reaction time under the low power MW irradiation. The same authors reported" the catalytic activity of related copper, iron, and vanadium systems with mixed-N,S pyridine thioether hgands. The Cu and Fe complexes proved to be useful catalysts in various MW-assisted alcohol oxidations with TBHP, at 80 °C. Thus, 5-containing ligands can also be used to create effective catalyst precursors. 

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