摘要:

Complexation of methylmercury(II) by sulfate, selenate, carbonate, sulfite, selenite, thiocyanate, selenocyanate, sulfide, and selenide in aqueous solution has been studied by proton magnetic resonance and Raman spectroscopy. Formation constants were determined for the SO42−, SeO42−, CO32−, SO32−, SeO32−, SeO3H−, SCN−, and SeCN−complexes from the pHdependence of the chemical shift and the199Hg−1H spin–spin coupling constant of the methyl group of CH3Hg(II) in solutions containing both CH3Hg(II) and ligand. The chemical shift and the199Hg–1H spin–spin coupling constant of the CH3Hg(II) in each of the complexes were also obtained from the same measurements. Proton magnetic resonance parameters were measured for several complexes with sulfide and selenide. The ligand donor atom in each of the complexes was identified using the formation constants, the199Hg–1H spin–spin coupling constant of the complexed methylmercury and the Raman spectral data. It is of particular interest that, in the selenite complex, the methylmercury is bonded to an oxygen atom whereas sulfur is the donor atom in the sulfite complex.

ISSN:0008-4042    

DOI:10.1139/v76-357

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The molecular conformation of−:CH2NO2is found to be planar with an extremely shallow potential curve to pyramidal inversion. This suggests that suitable substituents could conceivably perturb the System into a pyramidal configuration corresponding to double minimum on the potential surface and that a chiral carbanion might therefore exist. Rotating the NO2group out of planarity by 90° raises the barrier to inversion at carbon by an appreciable amount.A Mulliken population analysis gives a charge distribution in which a substantial portion of the negative charge has shifted from carbon to oxygen; this is consistent with the well-known tendency of nitronate ions to undergo simultaneous competitive protonation on carbon and oxygen.

ISSN:0008-4042    

DOI:10.1139/v76-358

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

A new inorganic ion exchanger, ferric arsenate, has been prepared under varied conditions. The product formed by the homogeneous precipitation method is most stable. Ion exchange selectivity with different metal ions (alkali metal and alkaline earth metal ions) is different and depends upon the hydrated radii of the exchanging cation. A straight line is obtained for the plot of capacity against hydrated radii of the cation in the same group. Some important separations are achieved quantitatively on the columns of ferric arsenate.

ISSN:0008-4042    

DOI:10.1139/v76-359

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Rate constants and activation parameters for the formation of the monocomplex of nickel(II) with isoquinoline in water, methanol, dimethylsulfoxide, andN,N-dimethylformamide were obtained from measurements by stopped-flow spectrophotometry. The data are compared with previously reported work by other authors for substitution at nickel(II) with related monodentate and multidentate ligands. The results in all solvents except dimethylsulfoxide are consistent with an Idmechanism. In dimethylsulfoxide substitution at nickel(II) proceeds in a similar way for all monodentate ligands but whether the mechanism is Idor D cannot be ascertained.

ISSN:0008-4042    

DOI:10.1139/v76-360

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The seven-coordinate complexes (L—L)M(CO)3X2(M = Mo, W; X = Br, I; (L—L) = cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2) were prepared and characterized.1H and13C nmr studies at 25 and −70 °C suggest that the complexes are nonrigid. Similarly1H nmr studies indicate the seven-coordinate (L—L)LMo(CO)2Br2complexes are also nonrigid. The (L—L)L2Mo(CO)Br2complexes (L is a monodentate phosphite or phosphine) are rigid at 25 °C and nonrigid at higher temperatures. Activation parameters are calculated for the motion of two of the complexes and possible mechanisms are discussed.

ISSN:0008-4042    

DOI:10.1139/v76-361

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Several acylate salts and noncyclic carbene complexes of manganese and rhenium, containing organogermanium ligands, have been prepared via the reactions of the cyclic germoxycarbene complexes of empirical formula Ph2GeM(CO)4COMe (M = Mn, Re) with the nucleophiles methyllithium or methoxide ion. In each case the observed product could be rationalized in terms of nucleophilic attack at germanium. Treatment of Ph2GeRe(CO)4COMe with methyllithium, followed by ethylation with aqueous Et3OBF4, affordedcis-Ph2MeGeRe(CO)4C(OEt)Me. The manganese analog of this product could be obtained if excess methyllithium were used in the first step. The use of a deficit of methyllithium, however, followed by ethylation, yieldedcis-Ph2FGeMn(CO)4C(OEt)Me. Solution infrared spectra have indicated that lithium methoxide and lithium bromide impurities in the methyllithium are involved in this reaction. The reaction of Ph2GeMn(CO)4COMe with sodium methoxide is presumed to involve nucleophilic attack at germanium to give a methoxygermanium species. Subsequent treatment with aqueous tetraethylammonium bromide gave the hydroxygermanium complex, [cis-Ph2(HO)GeMn(CO)4C(O)Me][Et4N]. Ethylation of the same species with aqueous Et3OBF4affordedcis-Ph2FGeMn(CO)4C(OEt)Me.

ISSN:0008-4042    

DOI:10.1139/v76-362

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The syntheses of a group of 2-(o-nitrophenyl)- and 2-(o-aminophenyl)-5,8-quinolinediones which are structurally related to the antitumor antibiotic streptonigrin are described. Ambiguities in the position of required nucleophilic displacements are resolved by independent synthesis. The rates of single strand cleavage of PM2 ccc-DNA (covalently-closed circular-DNA) induced by these compounds are compared, which correlates with antitumor activity. The 2-(o-nitrophenyl) derivatives give consistently more rapid DNA cleavage than the 2-(o-aminophenyl) compounds. The autoxidations of the dihydroxyquinolines are subject to selective catalysis by Cu2+on. 2-(o-Aminophenyl)-7-amino-6-methoxy-5,6-quinolinedione which has a substitution pattern most closely resembling streptonigrin also closely parallels the rate of scission of DNA of the latter in the presence of NADPH.

ISSN:0008-4042    

DOI:10.1139/v76-363

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

Fractionation of the carbon isotopes occurs during the oxidation of oxalate by permanganate in aqueous sulfuric acid. The isotope effect, expressed ask12/k13, rises from near unity in the very early stages of the reaction, to reach a value of 1.037 ± 0.001 after completion of the induction period. Addition of fluoride prolongs the induction period, and reduces the isotope effect to values near 1.000. These observations are consistent with there being two essentially independent paths for formation of carbon dioxide. The first, operative in the early stages, involves rate-controlling electron transfers from Mn(VI) or Mn(IV) to the oxalate ion, while the second involves oxidative decomposition of an oxalate complex of Mn(III), for which the rate-controlling step is C—C bond rupture.

ISSN:0008-4042    

DOI:10.1139/v76-364

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The formation of carbon dioxide by photolysis of aqueous solutions of ferric oxalate is accompanied by carbon isotopic fractionation.12C appears preferentially in the evolved CO2, but the isotope effect depends markedly on the wavelength of the light used. Fractionation is essentially zero (k12/k13 = 1.001) at 366 nm, and increases with wavelength, reaching 1.050 at 520 nm. It is proposed that this variation of isotopic discrimination arises from the differing properties of the excited levels formed by photochemical activation.

ISSN:0008-4042    

DOI:10.1139/v76-365

出版商:NRC Research Press    

年代:1976

数据来源: NRC

摘要:

The title compounds are conveniently obtained from the corresponding diones by the stereoselective hydrogenation with Urushibara nickel A catalyst in cyclohexane.

ISSN:0008-4042    

DOI:10.1139/v76-366

出版商:NRC Research Press    

年代:1976

数据来源: NRC