Octahedral cobalt(III) complexes in dipolar aprotic solvents. II. Association between cis- and trans-dichlorobisethylenediamine cobalt(III) cations,[Co en2 Cl2]+, and chloride and bromide ions in the solvents NN-dimethylformamide, dimethyl sulphoxide, and LVN-dimethylacetamide

1966 ◽  
Vol 19 (1) ◽  
pp. 43 ◽  
Author(s):  
WA Millen ◽  
DW Watts
Keyword(s):  
Spectrophotometric Method ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Dimethyl Sulphoxide ◽  
Aprotic Solvents ◽  
Ion Association Constants ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

Ion association constants at 30� have been determined for the cis-[Co en, Cl2]+Cl- ion pair in NN-dimethylformamide (DMF), NN-dimethylacetamide (DMA), and at 20.0�, 25.0�, and 30.0� in dimethyl sulphoxide (DMSO), by a spectrophotometric method. Association constants for the cis-[Co en2 Cl2]+Br- and the trans- [Co en2 Cl2]+Cl- ion pairs have also been determined in DMF at 30�.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. III. A new spectrophotometric method for the determination of ion association constants

1966 ◽  
Vol 19 (1) ◽  
pp. 51 ◽  
Author(s):  
WA Millen ◽  
DW Watts
Keyword(s):  
Spectrophotometric Method ◽  
Association Constant ◽  
Ion Association ◽  
Chloride Ion ◽  
Association Constants ◽  
Aprotic Solvents ◽  
Extinction Coefficients ◽  
Ion Association Constants ◽  
Dipolar Aprotic Solvents

A spectrophotometric method for the evaluation of ion association constants has been developed. This method involves the preparation of solutions containing only the compound under consideration. A function relating the association constants to the concentration of compound and extinction coefficients has been derived. The association constants are best determined by an iterative method using a computer. The association constant for the cis-diohlorobisethylenediaminecobalt(111) cation, cis-[Co en2 Cl2]+, and chloride ion in NN-dimethylformamide (DMF) at 30� has been calculated by this new method and is compared with that of another established procedure. The association constant has also been determined for the association of cis-[Co en2 Cl2]+ and iodide in DMF at 30�.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. IV. Solvolysis and isomerization of dibromobisethylenediaminecobalt(III) ions inanhydrous NN-dimethylformamide and NN-dimethylacetamide

1966 ◽  
Vol 19 (6) ◽  
pp. 935 ◽  
Author(s):  
WR Fitzgerald ◽  
DW Watts
Keyword(s):  
Concentration Dependence ◽  
Ion Association ◽  
Ion Pair ◽  
Aprotic Solvents ◽  
Equilibrium System ◽  
Lower Stability ◽  
Bromide Ion ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

The equilibrium system (SOL)+Br-+cis-[CoBr2 em]+ = cis-[CoBr(SOL) en2]2++2Br-   =trans[CoBr2en2]2++Br-+SOL where SOL represents either of the solvents NN-dimethylformamide (DMF) or NN-dimethylacetamide (DMA), has been studied. The compounds cis- [CoBr(DMF) en2](ClO4)2, and cis-[CoBr(DMA) en2]XO3,ClO4, have been isolated and thus it has been possible to study these equilibria using as starting materials both the cis- and trans-dibromo complexes (cis- and trans-[CoBr2 en2]+) and the solvento complexes (cis-[CoBr(DXA) en2]2+ and cis-[CoBr(DMF) en2]2+). The mechanism of the bromide entry reactions cis-[CoBr(SOL) en2]2+ +Br- = cis- and trans-[CoBr2 en2]++SOL is bimolecular in DMA while in DMF the reaction is dissociative: the rate showing bromide concentration dependence only in the concentration range where ion association is not complete. In both systems the isomerization proceeds mainly through the solvento complex; in dimethylacetamide there is evidence for a seven-coordinated intermediate. The isomerization equilibria are found to be bromide concentration dependent, cis-[CoBr2 en2]+ being favoured by high bromide concentrations. This is consistent with the lower stability of the trans-[CoBr2 en2]- ion pair with bromide ion.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. VI. Spectrophotometric determination of ion association of halide ions with cis-chlorodimethylformamidebisethylenediaminecobalt(III) ion and cis-chlorobromobisethylenediaminecobalt(III)ion in anhydrous NN-dimethylformamide

1966 ◽  
Vol 19 (6) ◽  
pp. 969 ◽  
Author(s):  
IR Lantzke ◽  
DW Watts
Keyword(s):  
Ion Association ◽  
Cobalt Complexes ◽  
Complex Salt ◽  
Ion Pair ◽  
Association Constants ◽  
Halide Ions ◽  
Kcal Mole ◽  
Ion Association Constants ◽  
Dipolar Aprotic Solvents

Using a spectrophotometric technique the ion association constants for three systems of octahedral cobalt complexes and halide ions have been determined at three temperatures in NN-dimethylformamide. The values of K, ΔH�, and ΔS� for each system have been calculated. At 30� they are as follows: cis-[CoCl(DMF) en2]2+ + Cl- ↔ ion pair K=1.51�0.03 x 104 1.mole-1(ΔH0= 0.93 � 0.02 kcal mole-1,ΔS�= 22.l+0.4 e.u) cis-[CoCl(DMF) en2]2++2Cl- ↔ ion triplet K= 1.21�0.05 X 106 1.2 mole-2(ΔH�=-3.8�0.lkcal mole-1, ΔS�=15.41� 0.5 e.u) cis-[CoCl(DMF) en2]2++Br- ↔ ion pair K= 9.20�0.18 X 103 1.1 mole-1(ΔH�=-7.2�0.lkcal mole-1, ΔS�=42� 1.0 e.u) cis-[CoBrCl en2]+ + Br- ↔ ion pair K = 690�l41. mole-1 (ΔH� = 1.27�0.03 kcal mole-1, ΔS�= 8.8�0.2 e.u.) The dependence of the measured K, the association constant, on the wavelength of measurement, small amounts of water in the solvent, and the anion of the complex salt, has also been investigated.

Octahedral chromium(III) complexes in dipolar aprotic solvents. II. The isomerization of cis- and trans-[CrCl2 en2]+ ions in anhydrous dimethyl sulphoxide

1968 ◽  
Vol 21 (12) ◽  
pp. 2895 ◽  
Author(s):  
DA Palmer ◽  
DW Watts
Keyword(s):  
Ion Association ◽  
Chloride Ion ◽  
Activation Energies ◽  
Dimethyl Sulphoxide ◽  
Aprotic Solvents ◽  
Ion Concentrations ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents ◽  
Exchange Data

The equilibria represented by the following equations: (See diagram in paper) have been studied in anhydrous dimethyl sulphoxide at various chloride ion concentrations. The mechanisms of the reactions are interpreted as dissociative and this assignment is consistent with the radiochloride exchange data. The kinetic and equilibria results are dependent on ion association which is separately treated by conductance measurements in the case of cis-[CrCl2 en2]+Cl-. Activation energies are recorded.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. VIII. The solvolysis of cis- and trans-[CoBr2 en2]+ ions in anhydrous dimethyl sulphoxideand mixtures of anhydrous dimethyl sulphoxide and NN-dimethylacetamide

1966 ◽  
Vol 19 (8) ◽  
pp. 1411 ◽  
Author(s):  
WR Fitzgerald ◽  
DW Watts
Keyword(s):  
Ion Association ◽  
Complete Removal ◽  
Activation Energies ◽  
Dimethyl Sulphoxide ◽  
Aprotic Solvents ◽  
Dimethyl Acetamide ◽  
Cis And Trans ◽  
Pure Dmso ◽  
Dipolar Aprotic Solvents

The solvolysis reactions (see diagram in article) have been studied in anhydrous dimethyl sulphoxide (DMSO) over a range of bromide concentrations and at various mole fractions of DMSO in NN-dimethyl-acetamide (DMA). The solvolysis of both isomers results in nearly complete removal of first bromide in pure DMSO while in DMA almost insignificant solvolysis occurs. The influence of ion association on the measured rates is discussed. Activation energies are presented for all reactions.

scholarly journals When spectroscopy fails: The measurement of ion pairing

2006 ◽  
Vol 78 (8) ◽  
pp. 1571-1586 ◽  
Author(s):  
Glenn Hefter
Keyword(s):  
Metal Ion ◽  
Chemical Speciation ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Spectroscopic Techniques ◽  
Association Equilibria ◽  
Solvent Molecules ◽  
Contact Ion Pairs

Spectroscopic techniques such as UV/vis, NMR, and Raman are powerful tools for the investigation of chemical speciation in solution. However, it is not widely recognized that such techniques do not always provide reliable information about ion association equilibria. Specifically, spectroscopic measurements do not in general produce thermodynamically meaningful association constants for non-contact ion pairs, where the ions are separated by one or more solvent molecules. Such systems can only be properly quantified by techniques such as dielectric or ultrasonic relaxation, which can detect all ion-pair types (or equilibria), or by traditional thermodynamic methods, which detect the overall level of association. Various types of quantitative data are presented for metal ion/sulfate systems in aqueous solution that demonstrate the inadequacy of the major spectroscopic techniques for the investigation of systems that involve solvent-separated ion pairs. The implications for ion association equilibria in general are briefly discussed.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. XI. Anation of cis-chlorodimethylformamidebisethylenediaminecobalt(III) by bromide ion, and solvolysis and isomerization of cis-and trans-bromochlorobisethylenediaminecobalt(III) ions in anhydrous N,N-dimethylformamide

1967 ◽  
Vol 20 (12) ◽  
pp. 2623 ◽  
Author(s):  
IR Lantzke ◽  
DW Watts
Keyword(s):  
Activation Parameters ◽  
Ion Association ◽  
Aprotic Solvents ◽  
Bromide Ion ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

The anation of the cis-chlorodimethylformamidebisethylenediaminecobalt(III) ion (cis- [CoCl(DMF) en2]2+) by bromide ion in N,N-dimethylformamide (DMF) has been studied. The reaction has an SNIIP1 mechanism, and when due allowance is made for ion association its activation parameters closely parallel those of other SNIIP anation reactions in DMF. The solvolysis and isomerization of the dichlorobisethylenediaminecobalt(III) ions (cis- and trans-[CoCl2 en2]+) and the bromochlorobisethylenediaminecobalt(III) ions (cis- and trans- CoBrCl en2]+) in DMF have been examined over a range of anion concentration. In all cases solvolysis reactions are important, although direct isomerization appears to become an important path for the reaction of the trans complexes at high anion concentrations. Solvolysis of the cis-[CoCl2 en2]+ ion involves an SN2 mechanism.1 The cis-[CoBrClen2]+, trans-[CoCl2 en2]+, and trans-[CoBrCl en2]+ ions all react by an SN1 mechanism.

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