摘要:

The lability of the metal–nitrogen bonds in the Cd(II), Zn(II), and Hg(II) complexes of (HO2CCH2)2N(CH2)nN(CH2CO2H)2(n = 2, 3, 4) has been investigated by proton magnetic resonance spectroscopy. The acetate methylenic protons of each of the complexes give rise to AB multiplet patterns, indicating the metal–nitrogen bonds to be inert on the n.m.r. time scale. From the temperature dependence of the multiplet patterns, the relative lability of the metal–nitrogen bonds in each series of complexes has been established. In the Cd(II) and Zn(II) complexes, the metal–nitrogen bonds become more labile as the size of the internal chelate ring increases whereas it becomes more inert in the Hg(II) complexes. Also, the mercury–proton coupling constants increase asnis increased from two to four, which is interpreted as evidence that the increased kinetic stability results from structural changes to a more linear N—Hg—N arrangement. The metal–nitrogen bonds in the Cd(II) complexes havingn = 3 and 4 is more labile than in the corresponding Zn(II) complexes. The thermodynamic stability patterns of the complexes are discussed in terms of their relative kinetic stabilities.

ISSN:0008-4042    

DOI:10.1139/v75-109

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Measurements of the equivalent conductivity of aqueous solutions of lithium, sodium, potassium, and cesium salts of carboxymethylcellulose (CMC) at 25 °C are reported. The degree of substitution of the CMC used was 0.86, concentrations of the four salts were varied from 5 × 10−4to 5 × 10−2equiv l−1. Results show a decrease of Λ with increasing concentration in each case. In the lower concentration range (up to 10−2N) this decrease is in close agreement with a limiting law for conductivity recently developed by Manning. Above 10−2Nthe decrease in Λ is less than the decrease predicted by the limiting law. The counterion dependence of Λ is accurately predicted by the theory, and a qualitative agreement is obtained when the theory is used to compare conductance data of polyelectrolytes with different charge densities.

ISSN:0008-4042    

DOI:10.1139/v75-110

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

N,N-Dimethylacetamide solutions of the cyclooctene complex [Rh(C8H14)2Cl]2, in the presence of excess chloride or diethylsulfide, are effective for the homogeneous hydrogénation of unsaturated carboxylic acids atca. 80 °C and 1 atm H2. Kinetic studies on the hydrogenation of maleic acid are consistent with a rate determining step involving oxidative addition of H2to square planar rhodium(I) olefin species. Rate constants and activation parameters agree with those determined previously from similar studies using corresponding rhodium(III) complexes and give confirmation that rhodium(I) catalysts are involved in the rhodium(III) systems. Discussion of the systems is limited by the somewhat uncertain nature of the catalysts; however, chlororhodate(I) species are involved in the chloride solutions, and bis(diethylsulfide) complexes appear likely in the sulfide systems.

ISSN:0008-4042    

DOI:10.1139/v75-111

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The photocyclization–oxidation reaction of 4-stilbenecarboxaldehyde gave 3-phenanthrenecarboxaldehyde. Similarly, irradiation of 3-stilbenecarboxaldehyde gave a mixture of 2-and 4-phenanthrenecarboxaldehyde. Irradiation of 1-(p-formylphenyl)-4-phenyl-1,3-butadiene gave a mixture of 1-(p-formylphenyl)naphthalene and 8-phenyl-2-naphthaldehyde. Photocyclization of 1-(m-formylphenyl)-4-phenyl-1,3-butadiene yielded 1-(m-formylphenyl)naphthalene, 5-phenyl-2-naphthaldehyde, and 8-phenyl-1-naphthaldehyde. The surprising nature of the photocyclization–oxidation reactions of stilbenes and 1,4-diphenyl-1,3-butadienes containing formyl substituents is discussed.

ISSN:0008-4042    

DOI:10.1139/v75-112

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Perfluoropinacol, (CF3)2C(OH)C(OH)(CF3)2, ionizes by loss of two protons, and the resulting dinegative ion (PFP2−) chelates to Ni2+, Pd2+, Pt2+, and Cu2+. A variety of stable neutral complexes may be isolated if the tetracoordination of the metal ion is completed with two monodentate or one bidentate nitrogen- or phosphorus-containing ligands; square-planar structures are invariably found. The structures of these complexes are contrasted with those of analogous halides, and it is concluded that electronic effects are predominant in determining them, although steric influences may sometimes be important. The ligand field strength of the perfluoropinacolato ion is approximately equal to that of the thiocyanate ion.The nickel complexes Ni(PFP)22−and (PFP)Ni(RNHCH2CH2NHR) react with donor solvents (water, methanol, pyridine, etc.) to give equilibria between four- and five-coordinate solvated species; six-coordinate species are not observed. This unusual behavior is attributed to the steric hindrance imposed by the bulk of the PFP2−ligand.

ISSN:0008-4042    

DOI:10.1139/v75-113

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Perfluoro(2,3-diphenylbutane-2,3-diol), CF3(C6F5)C(OH)C(OH)(C6F5)CF3, prepared by the reductive dimerization of C6F5COCF3, has been separated intomeso- andDL-isomers and the latter resolved via its cinchonidine salt into optical enantiomers. The doubly ionized diol, PDBD2−, acts as a dinegative, chelating, ligand, and neutral complexes of the form (PDBD)-ML2may be isolated, whereLis a neutral nitrogen- or phosphorus-containing ligand and M = Ni2+or Cu2+. Use of the resolved diol enables optically active metal complexes to be prepared, and from their o.r.d./c.d. spectra we assign an absolute configuration to the diol. The partially fluorinated diols CF3(C6H5)C(OH)C(OH)(C6H5)CF3and CH3(C6F5)C(OH)C(OH)(C6F5)CH3have also been prepared from the appropriate ketones. The former, which appears to be exclusively themeso-isomer, has more limited chelating ability than the fully fluorinated analog, while the latter shows no ligand properties; these differences are ascribed to the reduced acidity resulting from the lower degree of fluorination.Nuclear magnetic resonance studies suggest hindered rotation of the C6F5groups through steric interaction with CF3groups in perfluoro(2,3-diphenylbutane-2,3-diol); an alternate explanation involving hydrogen bonding from the hydroxylic proton to aromatic fluorine atoms is considered less likely.

ISSN:0008-4042    

DOI:10.1139/v75-114

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The rates of formation of hydroxy-9,10-anthraquinone-2-sulfonates, produced by irradiation of neutral and alkaline aqueous solutions of 9,10-anthraquinone-2-sulfonate (A) at 365 nm, have been measured for solutions with initial [A] ranging from 5 × 10−5to 8 × 10−2 mol dm−3, saturated with either O2, air, or N2. The rate of monohydroxylation was independent of the saturating gas and, for neutral solutions absorbing all the incident light, increased with increasing initial [A] reaching a constant maximum quantum yield of 0.08 above 2 × 10−2 mol dm−3. In 0.1 mol dm−3aqueous NaOH solution, the rate was about three times larger but had not attained a limiting value at the maximum [A] imposed by its solubility. Dihydroxy-9,10-anthraquinone sulfonates are proposed to arise from reaction of O2with an intermediate, rather than by further hydroxylation of monohydroxy products. The rate of dihydroxylation decreased on increasing [A] above 5 × 10−4 mol dm−3, becoming essentially zero at high concentrations.

ISSN:0008-4042    

DOI:10.1139/v75-115

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Nitrosonium pentanitratoholmate(III), (NO)2Ho(NO3)5, was prepared from holmium metal and dinitrogen tetroxide in anhydrous ethyl acetate. Its crystals are monoclinic witha = 8.094,b = 11.979, c = 14.170 Å and β = 104.7°,Z= 4, space groupP21/c. The structure was solved by the heavy-atom method and refined by full matrix least-squares methods to anRvalue of 0.085 for 1514 observed reflections measured on the G.E. XRD-6 diffractometer. The structure consists of one Ho(NO3)52−and two NO+ions. The holmium is 10-coordinated by five essentially symmetric bidentate nitrate groups which arrange themselves in a trigonal bipyramidal fashion around the metal with a mean Ho—O distance of 2.45 Å. The two NO+ions per metal occupy slightly different environments and give rise to two i.r. bands at 2250 and 2285 cm−1, attributable to the (N, O+) stretching vibration. The mean N—O distance within these ions is 1.00 Å.

ISSN:0008-4042    

DOI:10.1139/v75-116

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

Carbon-13 chemical shift data have been obtained for a number of isothiazole, benzo[c]isothiazole, 1,2-dithiole, and 1,3-dithiole derivatives. A number of these compounds are thiones and the chemical shifts of the C=S carbons are discussed in the light of recent attempts to predict such chemical shifts from those of the analogous carbonyl compounds. Comparisons of substituent chemical shift (s.c.s.) effects in these heterocyclic compounds with those in simpler aromatic or conjugated systems have been made and additivity correlations tested in a number of cases.

ISSN:0008-4042    

DOI:10.1139/v75-117

出版商:NRC Research Press    

年代:1975

数据来源: NRC

摘要:

The mechanism of the C-21 hydroxylation of progesterone (1a) byAspergillusnigerATCC 9142 to give 11-deoxycorticosterone (1b) has been studied by the use of progesterone derivatives and of C-21 deuterium labelled progesterones. The requirement of the C-21 hydroxylase system for a C-20 carbonyl group is demonstrated and the possibility of the involvement of this group, in the C-20,21 enol form, in the C-21 hydroxylation reaction has been discussed. However, on the basis of the observed deuterium isotope effect (KH/KD = 1.25), a mechanism for the microbial C-21 hydroxylation reaction is proposed in which the rate-determining step is the direct insertion of oxygen into a C-21 carbon–hydrogen bond and not one involving enolization of the C-20 carbonyl.In addition, C-11α and C-15β hydroxylation of both 20α- and 20β-hydroxypregn-4-ene-3-one (2aand2b) byA.nigerhas been observed.

ISSN:0008-4042    

DOI:10.1139/v75-118

出版商:NRC Research Press    

年代:1975

数据来源: NRC