Octahedral chromium(III) complexes in dipolar aprotic solvents. I. The isomerization of cis- and trans-Dichlorobisethylenediamine-chromium (III) ions in anhydrous NN-dimethylformamide

1967 ◽  
Vol 20 (1) ◽  
pp. 53 ◽  
Author(s):  
DA Palmer ◽  
DW Watts
Keyword(s):  
Activation Parameters ◽  
Chloride Ion ◽  
Kinetics And Mechanism ◽  
Significant Part ◽  
Aprotic Solvents ◽  
Free Chloride ◽  
System Activation ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

The kinetics and mechanism of the isomerization of cis- and trans- dichloro- bisethylenediaminechromium(III) ions, cis- and trans-[CrCl2 en2]+, have been investigated in anhydrous NN-dimethylformamide (DNF). The complex cis- chlorodimethylformamidebisethylenediaminechromium- (III), cis-[CrCl(DMF) en2]2+, is found to be a necessary intermediate and to remain a significant part of the system at equilibrium. The equilibria are found to depend on the concentration of free chloride ion as has been found in the comparable cobalt system.��� Activation parameters have been determined for isomerization reactions using both the cis- and trans-(CrCl2 en2)+ ions as starting materials and for the chloride entry reaction into the cis-[CrCl(DMF) en2]2+ ion which has been isolated as cis-[CrCl(DMF) en2](ClO4)2,R2O.

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.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. V. The substitution of chloride and thiocyanate into the cis-chlorodimethylformamidebisethylenediaminecobalt(III) ion in anhydrous NN-dimethylformamide

1966 ◽  
Vol 19 (6) ◽  
pp. 949 ◽  
Author(s):  
IR Lantzke ◽  
DW Watts
Keyword(s):  
Chloride Ion ◽  
Ion Pair ◽  
Kinetics And Mechanism ◽  
Aprotic Solvents ◽  
Dissociative Mechanism ◽  
Thiocyanate Ion ◽  
Dipolar Aprotic Solvents ◽  
Chloride Concentrations

The kinetics and mechanism of the substitution of chloride ion and thiocyanate ion into the cis-chlorodimethylformamidebisethylenediaminecobalt(111) ion, cis-[CoCl(DMF) en2]2+, have been studied in ,NN-dimethylformamide (DMF). The chloride entry shows mixed kinetics which are accounted for by two paths, a slow ion pair dissociation, and a fast bimolecular attack of chloride on an ion pair. The steric course of the reaction, which is chloride dependent, shows that the ion pair dissociative mechanism is more important at low chloride concentrations. The thiocyanate entry shows similar characteristics. Thiocyanate enters faster than chloride in the bimolecular path, but in the ion pair dissociative path, which is significant at lower anion concentration, both chloride and thiocyanate enter at the same rate.

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. 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. XIII. The isomerization of cis- and trans-Dibromobis(ethylenediamine)cobalt(III) ions, [CoBr2 em2]+, in anhydrous sulpholane

1968 ◽  
Vol 21 (3) ◽  
pp. 595 ◽  
Author(s):  
WR Fitzgerald ◽  
DW Watts
Keyword(s):  
Equilibrium Constants ◽  
Activation Parameters ◽  
Ion Pair ◽  
Pair Formation ◽  
Isomerization Reaction ◽  
State Entropy ◽  
Enthalpy Changes ◽  
Solvent Molecules ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

The isomerization of cis- and trans-[CoBr2 en2]+ has been studied in anhydrous sulpholane (tetramethylene sulphone). No evidence has been found for the presence of species containing coordinated solvent molecules, and the mechanism of isomerization of both isomers is interpreted as SNl the rates being influenced by ion-pair formation. Activation parameters have been measured for the isomerization of both species at various bromide concentrations. Equilibrium constants and standard state entropy and enthalpy changes for the isomerization reaction and for the formation of the cis-[CoBr2 en2]+ .......Br- ion pair have been measured.

Sign in / Sign up

Export Citation Format

Share Document