Sulfoxide complexes elements

In the chemistry of main-group element sulfoxide complexes, a relationship between Aj/(S=0) and the enthalpy of formation of the sulfoxide complex has been derived (159). The applicability of the equation has only been examined for O-l SO complexes, and the constraints on using Ai (S=0) as a measure of metal-ligand bond strength should be borne in mind during its application. 

Studies of sulfoxide complexes of other actinide elements have appeared, (38, 40), but insufficient data are available to make any meaningful comparisons along the series. Work on the solvent extraction of actinide elements by sulfoxides has been reported (423). 

The stem-loop structure in the noncoding 3 region of selenoprotein mRNAs has also been termed a SECTS element in mammals although it has a different overall structure. ° In silica analysis of the human genome sequence, using this consensus SECTS element along with the presence of the characteristic UGA codon within an exon, has led to the discovery of several new selenoproteins, including a selenium-dependent methionine sulfoxide reductase. It has been shown that a specific complex exists for selenoprotein synthesis that shuttles between the nucleus and the cytosol. This possibly protects the preformed complex for nonsense-mediated decay to allow for more efficient selenoprotein synthesis. The specific tRNA needed for selenocysteine... 

Miscellaneous ligands so far incorporated into the polystyrene matrix include imidazolyl [21], 2-amido oxime [22], thioether and sulfoxide moieties [23]. The procedure is simple and essentially involves the halogen-replacement of Cl- or Br- from polystyrene matrix, bearing CH2C1, or Br- groups. Mostly, first row transition element salts undergo facile complexation with these modified polystyrene matrices [21] (Fig. 11). 

Much work has been devoted to the halide complexation of these elements in non-aqueous media. Equilibrium and calorimetric measurements for the formation of the [MX ](n-2) (M = Zn or Cd X = Cl, Br, I or SCN n = 1-4) anions in dimethyl sulfoxide (DMSO) have shown that stability constants follow the same order, but are much larger than those found for aqueous solution zinc exhibits an enhanced hardness as an acceptor in DMSO as compared to cadmium. Calorimetric measurements indicate a change from octahedral to tetrahedral coordination with increasing halide concentrations.1002-1006... 

Sulfoxides were found in the weak bases and the neutral Lewis bases. The presence of sulfoxides in the bases is explained by their weakly basic character (21). The presence of sulfoxides in the neutral Lewis bases probably results because the sulfur-oxygen bond is extremely polar and may complex with ferric chloride. Elemental analysis of the subfractions (discussed later) suggests that the sulfoxides are concentrated by the separation scheme and are not oxidation products that occur after the separation. The totals which are in excess of 100% reflect the degree of multifunctionality as well as possible errors in VPO molecular weight. 

This structure is most likely responsible for the fact that when the complex is dissolved in hot solvents (dimethylformamide, ethanol, pyridine, dimethylacet-amide, or dimethyl sulfoxide), elemental sulfur and a dark residue are produced. 

Complexes for most d-block elements have been prepared and a recent review (1) updating that of Reynolds (2), summarises these. Considerations of the hard and soft properties of the donor atoms allow us to predict that, in general, sulfoxides should bind via oxygen to the hard first-row transition metals and via sulfur to soft metals, such as those of Group VIII. Both Steric and electronic effects have been shown to dictate the choice of donor atom and these effects may be summarized -... 

To 100 ml of an aqueous solution containing a-cyclodextrin (1.2-1.7 x 10 mol/1) or g-cyclodextrin (2.8-3.0 x 10 2 mol/1), equimolar amounts of ethyl trans-cinnamate were added at 40 C and dissolved by stirring for 40 min. After stirring for 2 hr at room temperature, the resultant white precipitates were filtered and dried in vacuo. Then the dried powders were washed with n-pentane to eliminate the ester not included and dried again. X-ray diffraction technique was used to prove the complex formation. Thus, the white crystalline powders were obtained with a- and 3-cyclodextrins in 80 and 95% yields, and composed of 0.5 or 1.0 mole of the guest molecule and of 1 mole of the corresponding host molecule, respectively. The contents of the ester in the complexes were determined by NMR in deuterated dimethyl sulfoxide and by elemental anaysis. 

Similar oxygen transfer reactions have been observed with sulfoxides and other element oxides, yielding the late transition metal-bound thioethers or the corresponding reduced ligands [31]. The pattern of the oxygen transfer has been established by and labeling studies in all these cases [23d], That both metal centers participate in the conversion of the element oxide is evident from the inability of either of the metal complex fragments linked by the Zr-M bond to affect these transformations on their own. 

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