Electron-transfer reactions in non-aqueous media. VII. Reduction of CoF(NH3)52+ and Co(HCOO)(NH3)52+ by copper(I) in dimethyl sulfoxide-water mixtures

1983 ◽  
Vol 36 (10) ◽  
pp. 1923 ◽  
Author(s):  
JMB Harrowfield ◽  
L Spiccia ◽  
DW Watts
Keyword(s):  
Electron Transfer ◽  
Dimethyl Sulfoxide ◽  
Aqueous Media ◽  
Mixed Solvents ◽  
Transfer Reactions ◽  
Aprotic Solvents ◽  
Aqueous Mixtures ◽  
Electron Transfer Reactions ◽  
Dipolar Aprotic Solvents ◽  
Sphere Mechanism

Previous work on the reduction of a series of cobalt(III) complexes by iron(II) in dipolar aprotic solvents and in aqueous mixtures has been extended to reduction by copper(I). The greater stability of copper(I) to disproportionation in these media has permitted the study of the reduction of CoF(NH3)52+ and Co(HCOO)(NH3)52+ in range of solvents over a number of temperatures with a precision not possible in previous studies in water. The results are consistent with an inner-sphere mechanism in which the copper(I) reductant is preferentially solvated by dimethyl sulfoxide to the exclusion of water in mixed solvents.

Electron-transfer reactions in non-aqueous media. II. Reduction of CoF(NH3)52+, CoCl(NH3)52+ and CoBr(NH3)52+ by iron(II) in dimethyl sulphoxide-water mixtures

1976 ◽  
Vol 29 (1) ◽  
pp. 97 ◽  
Author(s):  
BA Matthews ◽  
DW Watts
Keyword(s):  
Electron Transfer ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Solvent Composition ◽  
Dimethyl Sulphoxide ◽  
Transfer Reactions ◽  
Octahedral Coordination ◽  
Electron Transfer Reactions ◽  
Kinetics Of

The kinetics of the reduction of the cobalt(111) octahedral complexes, CoF(NH3)52+, CoCl(NH3)52+ and CoBr(NH3)52+, by iron((11) in various Me2SO-H2O mixtures have been studied over a range of temperatures. The activation parameters obtained for the chloro and bromo systems are consistent with a change in the stereochemistry of the iron (11) atom in the bridged intermediate from octahedral in water to tetrahedral with increasing Me2SO concentration. The fluoro system, however, has activation parameters which are less sensitive to solvent composition and consistent with the iron(11) atom maintaining octahedral coordination.

Electron-transfer reactions in non-aqueous media. III. Reduction of CoF(NH3)52+, CoCl(NH3)52+ and CoBr(NH3)52+ by iron(II) in N,N-dimethylformamide

1976 ◽  
Vol 29 (3) ◽  
pp. 551 ◽  
Author(s):  
BA Matthews ◽  
JV Turner ◽  
DW Watts
Keyword(s):  
Electron Transfer ◽  
Equilibrium Constants ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Transfer Reactions ◽  
Octahedral Coordination ◽  
Electron Transfer Reactions ◽  
Reversible Formation

The reduction of the cobalt(111) octahedral complexes CoF(NH3)52+, CoCl(NH3)52+ and CoBr(NH3)52+ by iron(11) in HCONMe2 proceeds through a mechanism involving reversible formation of a halide bridged binuclear intermediate prior to electron transfer and decomposition of the intermediate to products. Values of the activation parameters for reduction and the equilibrium constants for formation of the bridged intermediate are consistent with a tetrahedral stereochemistry for the iron(11) atom in the bridged intermediate for the chloro and bromo systems. However, for the fluoro system these values are consistent with the iron(11) atom maintaining octahedral coordination. These results are compared to those obtained in Me2S0.1,2

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