Reactivity of the carbonate radical toward metal complexes in aqueous solution
- Univ. of Michigan, Flint
Rate constants for the reaction of CO/sub 3/H radicals in neutral and mildly acidic aqueous solution with labile aquo ions (Co/sub aq//sup 2 +/, Zn/sub aq//sup 2 +/, Ni/sub aq//sup 2 +/, Cu/sub aq//sup 2 +/, Mn/sub aq//sup 2 +/, and two Co(II) diaquo-macrocyclic complexes) and 19 substitution-inert amine complexes of Cr(III), Co(III), Rh(III), Ir(III), and Ru(III) have been measured at 23/sup 0/C using the flash photolysis technique. The value of k for the labile ions depends upon the oxidation potential of the complex and rate of exchange of the aquo ligands. Complexes of the form M/sup III/(NH/sub 3/)/sub 5/OH/sup 2 +/ are more reactive than their conjugate acid and, generally, than their M/sup III/(NH/sub 3/)/sub 5/Cl/sup 2 +/ analogue. Complexes with an accessible higher oxidation state (Ir(NH/sub 3/)Cl/sup 2 +/) or an easily oxidizable ligand (Co(NH/sub 3/)/sub 5/NO/sub 2//sup 2 +/) have high rates (>10/sup 7/ M/sup -1/ s/sup -1/). The reaction of CO/sub 3/H with Co(NH/sub 3/)/sub 5/Cl/sup 2 +/ (k = 2.0 x 10/sup 6/ M/sup -1/ s/sup -1/) and Co(NH/sub 3/)/sub 5/Br/sup 2 +/ (k = 5.7 x 10/sup 6/ M/sup -1/ s/sup -1/) leads to ligand substitution; in contrast, the reaction of these complexes with OH radicals leads solely to the formation of Co/sub aq//sup 2 +/. It is suggested that CO/sub 3/H and OH radicals react with these complexes by initially coupling with the halide ligand; subsequent intra- and intermolecular processes lead to the final products.
- OSTI ID:
- 6141256
- Journal Information:
- J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 82:25; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400600* -- Radiation Chemistry
CARBON COMPOUNDS
CARBONATES
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
COBALT COMPOUNDS
COPPER COMPOUNDS
DECOMPOSITION
IRIDIUM COMPOUNDS
KINETICS
MANGANESE COMPOUNDS
NICKEL COMPOUNDS
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOLYSIS
REACTION KINETICS
RHENIUM COMPOUNDS
RUTHENIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS