摘要:

An identifiable relationship exists between the absolute configuration of chiral diamine ligands and the circular dichroism of their complexes with palladium(II) and platinum(II). Complexes which contain simpleC-substituted diamines with theR-absolute configuration show positive circular dichroism in the region associated with the1A1g → 1Egtransition, both in solution and the solid state. There is no general consistency in the sign of the1A1g → 1A2gtransition, and only for solution does the sign of the net circular dichroism show a correlation with the absolute configuration of the ligands.

ISSN:0008-4042    

DOI:10.1139/v79-011

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

A novel method for the assessment of the Ph4As+/Ph4B−assumption for free energies of transfer of single ions has recently been suggested by Treiner, and used by him to deduce that the assumption is not valid for transfers between water, propylene carbonate, sulpholane, dimethylsulphoxide,N-methyl-2-pyrrolidone, and perhaps also dimethylformamide. The basis of the method is the estimation of the free energy of cavity formation by scaled-particle theory, together with the hypothesis that the free energy of interaction of Ph4As+(or Ph4B−) with solvent molecules is the same in all solvents, ΔGt0(int) = 0. It is shown in the present paper that (a) whether or not the Ph4As+/Ph4B−assumption applies to transfer to a given solvent depends on which other solvent is taken as the reference solvent in Treiner's method, (b) the calculation of the cavity free energy term by scaled-particle theory and by the theory of Sinanoglu – Reisse – Moura Ramos (SRMR) yields values so different that the method cannot be considered reliable, (c) the calculation of cavity enthalpies and entropies for Ph4As+or Ph4B−by scaled-particle theory yields results that are chemically not reasonable, (d) the hypothesis that ΔGt0(int) = 0 conflicts with SRMR theory, and (e) the conclusions reached by Treiner are not in accord with recent work that in general supports the Ph4As+/Ph4B−assumption for solvents that are rejected by Treiner.

ISSN:0008-4042    

DOI:10.1139/v79-012

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The kinetics of the binding of Br−to Fe(III) were studied as a function of [H+] and [Br−] on a high pressure laser temperature jump apparatus up to 2.76 kbar. At constant [H+] the pseudo first order rate constant for formation of FeBr2+showed little dependence on pressure or on [Br−] over the range 0.02 to 1.9 M. The results were interpreted by a mechanism in which Fe3+and FeOH2+react with Br−to form ion pairs prior to formation of their inner sphere complexes. The kinetic activation volume for the conversion of the Fe3+, Br−ion pair to FeBr2+appears to be quite negative, consistent with an associative interchange (Ia) mechanism.

ISSN:0008-4042    

DOI:10.1139/v79-013

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Mercury(II) acetate complexes of the type (R3P)nHg(OAc)2, wheren = 1 and 2, and R3P = (p-tolyl)3P, (p-F-C6H4)3P, Ph2MeP, Ph2EtP, and PhEt2P have been prepared in good yields. Only the 1:1 adduct is formed with (o-tolyl)3P. Conductance measurements in nitromethane show that these complexes are non-electrolytes. The 1:1 adducts are monomeric in dichloroethane but the 1:2 adducts are extensively dissociated. Tentative assignments for ν(COO), ν(Hg—O), ν(Hg—P) are made from the infrared and Raman spectral data. The correlation of the coordination chemical shifts, Δδ(31P), with the coupling constants1J(199Hg–31P) of the complexes is discussed with respect to the bulkiness and the basicity of the phosphine ligands.

ISSN:0008-4042    

DOI:10.1139/v79-014

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Triphenylphosphine reacts with mercury(II) acetate and fluoroacetates to form complexes of the types Ph3PHg(O2CR)2, (Ph3P)2Hg(O2CR)2, and (Ph3P)3Hg(O2CR)2, where R = CH3, CH2F, CHF2, or CF3. The 1:1 and 2:1 have been isolated and characterized by elemental analysis, molecular weight, and conductance measurements and by vibrational and nmr spectroscopic studies. The formation of the 3:1 complexes is inferred by31P nmr spectral measurements at 183 K. Both the 1:1 and 2:1 complexes are indicated to be monomeric molecular species in which the O2CR groups are bidentately bonded to mercury. The Hg—O and Hg—P stretching frequencies for these complexes have been assigned by infrared and Raman spectral measurements. The199Hg–31P spin–spin coupling constants and the31P coordination chemical shifts for the 1:1 as well as the 2:1 complexes increase in the order: O2CCH3 < O2CCH2F < O2CCHF2 < OCCF3Correlations between1J(199Hg–31P) values,31P coordination chemical shifts, and the pKavalues for the carboxylic acids are discussed.

ISSN:0008-4042    

DOI:10.1139/v79-015

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Ab initiomolecular orbital calculations using STO-3G and 4-31G basis sets have been performed for cis-HNNH andcis-CH3NNCH3as a function of angle about the nitrogens, and for the cyclic molecules diazirine (1a) and diazetine (1b); in all cases the ground states of the neutral system and of the cation and anion and the first singlet excited state of the neutral molecule were studied. The optimum HNN angles for the cation and neutral excited n − π* singlet state of HNNH are significantly larger than for the anion and neutral ground state. Thus the ionization energy and singlet excitation energies forcis-azo Systems pass through a maximum in the region around a nitrogen angle of about 100°. The implications of these calculations to the excitation and photoelectron spectra of cycliccis-azo compounds is discussed in some detail, as is the origin of the variation in stability with angle of the n −molecular orbital. Due to the heavy involvement of carbon, the n −MO in diazirine does not follow the angle trends established by the HNNH calculations.

ISSN:0008-4042    

DOI:10.1139/v79-016

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The solution equilibria of di- and tetrapeptides containing tyrosine and glycine residues have been investigated in absence and presence of cobalt(II), nickel(II), and copper(II) ions. The equilibrium constants have been determined by pH titration at 30 °C and μ = 0.1 M(NaNO3) in 80% by weight DMSO – water mixed solvent. Protons are ionized from terminal (protonated amino and carboxyl) groups as well as from peptidic nitrogens. Complexes of 1:1 composition of metal ion – tetrapeptides were formed in quite a wide range of pH; also 1:1 complexes of the metal ions – dipeptides were formed in solution under the same conditions. Other higher complexes cannot be proved to form in the pH range studied. The complexes of these metal ions with glycine andO-Bzl-L-tyrosine were also studied under the same experimental conditions as control experiments and their equilibrium constants were calculated.

ISSN:0008-4042    

DOI:10.1139/v79-017

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The four protonation constants are reported for the dianion of ethylenediamine-N,N′-diacetic acid(H2L),25°C,I = 0.10 M(KNO3), (logki = 9.60, 6.51, 2.12, 1.3). logK(potentiometric) and ΔH(calorimetric) data are reported for the formation of the complexes [ML], M = Mn2+, Zn2+, Cd2+, and Pb2+(logK = 6.87, 10.99, 9.16, and 10.66; ΔH = −2.9, −24.4, −16.7, and −28.0 kJ mol−1respectively). The complexes [ZnL] and [PbL] undergo (aqua) proton dissociation reactions,logKD = −10.56 and −11.02, ΔHD = +60.7 and +38.5 kJ mol−1, respectively. Potentiometric and nmr studies indicate that the ligand undergoes a slow (metal catalysed) hydrolysis or rearrangement in aqueous acid.

ISSN:0008-4042    

DOI:10.1139/v79-018

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

The reaction of 2,4-dinitrobenzenesulphenyl chloride with eight alkyl 1,3-disubstituted allenes in methylene chloride solution has been investigated. In contrast to earlier reports, attack by sulphur is found to occur exclusively at the central allenic carbon. The direction of approach of sulphenyl chloride leads preferentially to the formation of theEisomers in accord with the concept of steric approach control. The ratio ofEtoZalkene is found to increase as the bulk of the substituent groupcisto the arylthio group increases. We observe, however, very little regioselectivity with respect to which of the mutually perpendicular π bonds of the allene system is attacked, suggesting the presence of an effective mechanism for transmission of inductive effects to the more distant double bond.

ISSN:0008-4042    

DOI:10.1139/v79-019

出版商:NRC Research Press    

年代:1979

数据来源: NRC

摘要:

Molecular motion in solidsym-triazine was investigated using continuous wave and pulsed1H nmr methods between 290 and 350 K. In addition, the potential energy profile of thesym-triazine molecule as a function of orientation in the crystal lattice was calculated. From the nmr results, only one motional process was identified, in-plane reorientation ofsym-triazine molecules with an activation energy of 15 kcal/mol. This is in agreement with the potential energy calculation which also shows that the reorientation takes place between equivalent sites.

ISSN:0008-4042    

DOI:10.1139/v79-020

出版商:NRC Research Press    

年代:1979

数据来源: NRC