Thioethers chelating ligands

The ligand mercaptoethyl pyridine forms a monomeric ZnL2 complex with the chelate ligand binding through the nitrogen and thioether sulfur.125... 

Several Pd11 complexes with thiolate or thioether derivative ligands have been studied to be applied in the hydroxycarbonylation reaction.394 Aminothiolate complexes of palladium with PPh3 catalyze the conversion of styrene to 2-phenylpropionic acid in high yield and excellent regioselectivity.644 Under mild conditions and in the presence of a catalytic amount of an S, TV-chelated palladium or//zo-amino-arenethiolate complex, styrene reacts with CO and oxalic acid or water to selectively give 2-phenylpropanic aid in high yield.645... 

The synthesis of N-(2-mercaptoethyl)-3,5-dimethylpyrazole and the workup procedure are performed in air, but the resultant thiol can best be stored under a nitrogen atmosphere. In air, the thiol is resistant to oxidation for several weeks, but the disulfide slowly crystallizes from the oil. According to the NMR spectra, the product is quite pure, but may still contain a small amount of 1,1,3,3-tetramethylurea (up to 5%). The reaction with 1,3-dichloro-2-propanol was carried out in a water/tetrahydrofuran mixture with sodium hydroxide, and appeared to proceed smoothly and in almost quantitative yields.2 This new reaction path to pyrazole-thioether ligands opens the road to the development of new chelating ligands. 

Chelating Ligands with Thioether Groups and Other Donor Atoms 553... 

The synthesis of several thioether pentadentate ligands (95) is described.149 Acid dissociation constants and metal-chelate formation for a series of divalent metals, as well as formation constants for dioxygen adducts of their cobaltous complexes, are also reported. 

A Ni amido complex supported by a thioether/thiolate chelating ligand that promotes the desoxygenation of CO, CO2, and SO2 has been described, (29). The product, NCO, and mechanism of CO2 reduction involving CO2 insertion into the Ni—bond, bear no resemblance to the enzymatic process. 

The kinetic behavior of the reductions of several Cu(II)N2S2 complexes, containing thioether/pyridyl chelate ligands, by ferrocene and l,r-dimethyl-ferrocene in acetonitrile points to the formation of a precursor complex prior to electron transfer.The rate constant for the oxidation of (hydroxyethyl)-ferrocene by [2-pyridyl(methylbis(2-ethyl)thioethyl)amine]copper(II) yields a [Cu(pmas)] self-exchange rate constant of 47 M s from the Marcus theory relation.The addition of NJ increases the rate of oxidation (F" and I" have no effect) by shifting the reduction potential upon the formation of [Cu(pmas)N3] and Cu(pmas)(N3)2 (NJ displacement of a thioether sulfur occurs in the latter species). The application of the Marcus relationship to the reductions of the [l,8-bis(2-pyridyl)-3,6-dithiaoctane]copper(II) complex by a series of Ru(II) ammine and bipyridyl complexes in 50% aqueous CH3OH yields a self-exchange rate constant of 0.63 s for the [Cu(pdto)] couple. " From the rate... 

The many synthetic methods available for preparing NHCs have allowed for their ready incorporation into an increasingly diverse set of multidentate ligands. The topic of chelating ligands containing NHCs has been covered in several reviews.Heteroleptic variations have included phosphines, amines, imines, pyridines, oxazolines, amides, alkoxides, aryloxides, thioethers, and other donors. 

With copper(II) S4-macrocycles and chelating ligands, there is no abnormally low barrier to electron transfer in reaction with cytochrome c(II), which suggests that there is no appreciable rate enhancement due to the thioether linkage. Oxidations of cytochrome c(II) by and CuCl" have also been examined. The ion binds to the protein but this bound copper is not involved in electron transfer. 

New chelate chiral phosphorus ligands provided a source for a large number of Rh and other metal-based catalysts. The bis(phosphinoalkyl-ether)arene and bis(phosphinoalkyl-thioether)arene ligands were synthesized allowing the preparation of symmetric bimetallic structures with Rh centers 26. ... 

Monodentate thioether ligands are relatively poor ligands towards Ni11. However, several Ni11 complexes with polydentate thioether ligands are known, where the coordination capability is enhanced by chelation. In particular, complexes with macrocyclic thioether ligands, which are discussed in Sections 6.3.4.10.l(iii) and 6.3.4.10.3, are very stable. 

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