DMSO solution complexes

Obviously, to model these effects simultaneously becomes a very complex task. Hence, most calculation methods treat the effects which are not directly related to the molecular structure as constant. As an important consequence, prediction models are valid only for the system under investigation. A model for the prediction of the acidity constant pfQ in aqueous solutions cannot be applied to the prediction of pKj values in DMSO solutions. Nevertheless, relationships between different systems might also be quantified. Here, Kamlet s concept of solvatochro-mism, which allows the prediction of solvent-dependent properties with respect to both solute and solvent [1], comes to mind. 

The best understood compounds are cis- and fra s-RuX2(DMSO)4 (X = Cl, Br). The fra s-isomers are thermodynamically less stable and isomerize in DMSO solution to the m-isomer, with first-order kinetics, probably via a dissociative mechanism. The reverse process, cis to trans, is catalysed by light. Syntheses for these and other DMSO complexes are shown in Figure 1.37 [108],... 

The FT-IR spectroscopic measurements shown that in most cases the -COO or -0 groups formed a bridge between two Sn central atom, and polymerization occurred. The pqs approximations proved the formation of complexes with Oh, Tbp, and structures. H NMR measurements performed in DMSO solution have shown that the polymeric structure of the complexes does not persist in solution, and depolymerization occurs.. ... 

A reverse cross-coupling reactions mediated by palladium was used to develop a colorimetric sensitive chemodosimeter for the detection of trace palladium (II) salts [93]. The decolorization of 4 is produced by a nucleophilic attack of ethanethiol in basic DMSO solutions. Palladium detection is done via thiol scavenging from the 4-ethanethiol complex leading to a color turn-on of the parent squaraine. Naked-eye detection of Pd(NC>3)2 is as sensitive as 0.5 ppm in solution, and the instrument-based detection can go as low as 0.1 ppm. 

The data obtained from this 170 study on the Re(V), also that obtained in DMSO solutions, can be correlated with results from previous X-ray crystallographic and infrared solid-state studies on these oxocyanorhenate(V) complexes and are summarized in Fig. 12. 

Reactions of potassium superoxide solubilized in apolar solvents with crown ethers (see Oxidation reactions, p. 356) are also frequently accompanied by elimination reactions. Thus, in DMSO solution, secondary alkyl bromides only yield olefins when treated with the K02 complex of dicyclohexyl-18-crown-6 (Johnson et al., 1978). Scully and Davis (1978) have studied the elimination of HC1 from N-chloramines with 18-crown-6-solubilized K02, KOH, and KOAc in ether solution (27). High yields of aldimines were obtained with K02,... 

It has a magnetic moment of 5.22 //B, which testifies a high spin (d6-e"3 d2a[l, four unpaired electrons) complex. [Fe(saldpt)] in dmso solution also displays a reversible Fe(II)/Fe(III) oxidation (E° = -0.29 V).96... 

In dmso solution these complexes also exhibit both the Co(II)/Co(III) oxidation and the Co(II)/Co(I) reduction, Figure 86, but only the Co(III) compound is completely stable.129... 

Table 10 Oxidation potentials (V vs. SCE) for the [Co11 (R-X-saldpt)] complexes in dmso solution...

The reactions with superoxide were studied in DMSO containing a controlled amount of water (.06%), which was in excess over the superoxide and complex concentrations 49). Water present in the DMSO solution plays an important role and enables the catal5rtic decomposition of O2. Under absolute water-free conditions only a stoichiometric reaction between O2 and the complex could be observed and the... 

The Fe + complex of the tetradentate NaO-donor tripodal ligand (168) provides a model for mononuclear nonheme bioactive sites. [Fe (168)Cl2], whose chloride ligands are substitution-labile, reacts with 2 in DMSO solution to give an Fe .02 species that may well be identical with the stable Fe 02 species obtained from the reaction of the iron(II) complex of (168) with 02. ... 

When ethylenediamme is. aided to a solution ofcobaltfll) chloride hexahydraic in concentrated hydrochloric acid, a Hue crystalline solid is obtained in 80% yield. Analysis of this compound shows ihal it contains 14.16% N. 12.13% C. 5.09% H. and 53.70% Cl. The effective magnetic moment is measured as 4.6 BM. The blue complex dissolves in water to give a pink solution, the conductivity of which is 852 ohm 1 cm mot"1 at 25 °C. The visible spectrum of a dmso solution of the complex his bands centered at 3217.5610. and 15,150 cm" (molar absorptivity = 590 mol-1 Lem-1), but for a water solution, the absorptions occur et 8000. —16.00031x119.400cm-I(nx)lar absorptivity = 5 mol-1 Lem-1). In u titration with sodium hydroxide, each mole of Ihe complex neutralizes four moles of base. Determine the formula and structure of the complex. Account for dll reactions and observations. 

NMR evidence has been provided for the formation of Meisenheimer adducts in DMSO solution from several mononitrothiophenes (70JHC1441, 74JHC97, 75JHC327). Interesting examples of the formation of spiro adducts have also been recorded (Scheme 137) (75JHC1083) one of these appears to be the first Meisenheimer complex observed at position 3 of thiophene. 

The complex species [Cd(SCN)2] and [Cd(SCN)3] have been investigated, and it is thought that the thiocyanate is coordinated to the metal via sulfur in DMSO solution, but that in aqueous solution it is coordinated through the nitrogen atom.1017... 

In order to show that the origin of this difference is not a function of the particular substrate analogue used, similar NMR relaxation studies have been performed with dimethyl sulfoxide (DMSO)1401 since the crystal structure of the enzyme-NADH-DMSO ternary complex is well resolved.1366 From the relaxation data, the distance between the methyl protons of DMSO and Co11 was calculated to be 8.9 0.9 A, again too great for direct coordination of the sulfoxide group to the metal ion. Since the cobalt enzyme appears to be functionally similar to the native enzyme, the difference is unlikely to be a direct result of substitution. One possibility is that there may actually be a difference between the solution and crystalline structure of the enzyme ternary complex, particularly since it is well established that the crystalline enzyme is 1000 times less active than in solution.1402... 

Characteristic perturbations of the C—N and V=0 stretching vibrations were detected following base-adduct formation. These perturbations (batho-chromic shifts of the V=0 stretch and C—N vibrations) also were detected in DMSO solutions of the VO(R2Dtc)2 complexes. 

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