Kinetics and stereochemistry of solvolysis of cis- and trans-dibromo- and bromochlorobis(ethylenediamine)chromium(III) complexes in dipolar aprotic solvents

1975 ◽  
Vol 14 (5) ◽  
pp. 1154-1160 ◽  
Author(s):  
W. G. Jackson ◽  
W. W. Fee
Keyword(s):  
Aprotic Solvents ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

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 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. 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 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.

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