Metals complexes, dimethylsulfoxide

The as)rmmetric proline-catalyzed intramolecular aldol cyclization, known as the Hajos-Par-rish-Eder-Sauer-Wiechert reaction [106,107], was discovered in the 1970s [108,109,110,111]. This reaction, together with the discovery of nonproteinogenic metal complex-catalyzed direct asymmetric aldol reactions (see also Sect 5.5.1) [112,113,114], led to the development by List and co-workers [115,116] of the first proline-catalyzed intermolecular aldol reaction. Under these conditions, the reaction between a ketone and an aldehyde is possible if a large excess of the ketone donor is used. For example, acetone reacts with several aldehydes in dimethylsulfoxide (DMSO) to give the corresponding aldol in good yields and enantiomeric excesses (ee) (O Scheme 17) [117]. 

Shortly after the report of the reaction of a rhodium carbonyl complex with O2 to give coordinated CO2, the catalytic oxidation of CO to CO2 was reported in a similar system [193]. Kiji and Furukawa reported that both [RhCl(COXPPh3)2] and [RhCl(COXMe2SO)2] catalyzed the oxidation of CO in benzene, ethanol, or dimethylsulfoxide. However, the rate was slow and the catalytic efficiency was poor. Reactions catalyzed by [RhCl(COXMe2SO)2] in benzene gave approximately 11m moles of CO2 per m mole of metal complex. The authors describe the reaction as involving (1) coordination of molecular oxygen, (2) reaction with CO in the coordination sphere, and (3) displacement of the product by unreacted CO. 

Low molecular weight higher functional substituted macrocyclic metal complexes (M = Co, Ni, Cu, Zn) were converted with other bifunctional compounds to polymers. By the reaction of tetraaminophthalocyanine in the presence of another diamine with benzenetetracarboxylic acid dianhydride, at first in dimethylsulfoxide (DMSO) soluble amide-carbocylic acid copolymers were obtained and after film casting and... 

Fernandez, E.J., Laguna, A., Lopez-de-Luzuriaga, J.M., Montiel, M Olmos, M.E. and Perez, J. (2005) Dimethylsulfoxide gold-thaDium complexes. Effects of the metal-metal interactions on the luminescence. Inorganica Chimica Acta, 358(14), 4293 300. 

Iodides of soft metal ions such as mercury (II) are essentially un-ionized in dimethylsulfoxide 54). This feature is due both to the strength of the Hg-I bond and the weakness of the Hg-DMSO bond which appears to occur through the sulfur atom of the DMSO molecule, as is known for the palladium (II) complex 5S). 

Divalent metal ions, reversible binding, 38 153 Dixenon cation, 46 68 Dizinc enzymes, 40 351-354 DMA, see Dicarbomethoxy acetylene DMAD complexes, see Dicarboxymethoxy dithiolene complexes DMAE, see Dimethylarsinoylethanol DMF, reduction potentials, 33 57 DMSO, see Dimethylsulfoxide DNA... 

Borabenzene anions can serve as n ligands to a thallium(I) center, as demonstrated by the work of Herberich et al. (183). Reaction of alkali metal borinates with thallium(I) chloride yields the pale yellow, sublimable complexes LVIa,b [Eq. (16)] (see Fig. 11), which are only sparingly soluble in nonpolar aprotic solvents but easily soluble in pyridine and dimethylsulfoxide (183). 

Depending on the nature of the catalyst, the transition-metal-catalysed isomerisation will proceed by an addition-elimination mechanism or by the formation of a it allyl complex followed by a 1,3-hydrogen shift (Scheme 2.7b). The equilibrium of the isomerisation lies strongly in favour of the propenyl ether because of resonance stabilisation between the oxygen lone pair and the it orbital of the double bond. Isomerisation can also be performed under strongly basic conditions by using potassium f-butoxide in dimethylsulfoxide (DMSO).18... 

The electrochemistry of the polymeric and isomorphous cobalt(II) and nickel(II) methylsquarates was also studied by Iwuoha et al. In aqueous solutions, they found evidence that both the nickel(II) methylsquarate and its cobalt analog were dissociated without any reversible redox processes occurring for the metal ions. However, the cyclic and Osteryoung square wave voltammograms, obtained using a Pt electrode for solutions of these complexes in dimethylformamide and dimethylsulfoxide, contained signals attributable to both ligand-based and metal-based redox processes 142). 

It was found that addition of hydroxide anion in dimethylformamide or dimethylsulfoxide to metal(II) corrole complexes results in the appearance of much sharper absorption bands relative to the starting compounds. These findings were considered consistent with the idea that an anionic, 18 Jt-electron aromatic corrole complex (e.g., 2.119) is formed as the result of what appears to be a formal deprotonation process (Scheme 2.1.25). That deprotonation actually occurs was inferred from acid-base titrations involving nickel(II) and copper(II) corroles. The conclusion that these species are anionic aromatic compounds came from an appreciation that their electronic spectra resemble those recorded for divalent metallo-porphyrins. In any event, the anion that results was found to be quenched upon acidification, regenerating the corresponding non-aromatic metallocorroles. ... 

A metal ion not infrequently implicated in superoxide-associated damage to cells is Fe ". It is known that Fe can form complexes with superoxide, thereby leading to the formation of peroxide or even possibly OH-radicals, which are highly damaging. It is also feasible that damage can result from the interaction of superoxide with other metal ions. Isolated mitochondria swell rapidly when incubated in the presence of Ca. Such cells can be protected for long periods by 10% dimethylsulfoxide, an agent which readily destroys peroxide. Suspensions of liver cells tolerate ischemic... 

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