Anion radical oxidation of nickel(II) macrocyclic complexes. Pulse radiolysis of (2,12-dimethyl-3,7,11,17-tetraazabicyclo(11. 3. 1)heptadeca-1(17),13,15-triene)nickel(II) in sodium bromide solution
The oxidation of Ni/sup II/(CR + 4H) (CR + 4H = 2,12-dimethyl-3,7,11,17-tetraazabicyclo(11.3.1)heptadeca-1(17),13,15-triene, ..cap alpha.. isomer) by Br/sub 2//sup -/ and subsequent chemistry of Ni(III) intermediates have been studied by pulse radiolysis. The initial electron transfer is diffusion controlled and results in an initial product which exhibits characteristics of a Ni(III)-Br/sup -/ adduct. The stability of this adduct, especially in acidic media, is dependent on bulk bromide concentration, demonstrating an equilibrium process of the form Ni/sup III/(CR + 4H)(Br/sup -/)(H/sub 2/O) + H/sub 2/O in equilibrium Ni/sup III/(CR + 4H)(H/sub 2/O)/sub 2/ + Br/sup -/, with K/sub eq/ = 360 M/sup -1/. The pK of dissociation for the aquated species is 4.0 +- 0.8. At pH > 5 displacement of the bound bromide is first order in (OH/sup -/) with a rate constant of 6 x 10/sup 9/ M/sup -1/ s/sup -1/. Disappearance of the Ni/sup III/(CR + 4H)(OH/sup -/) intermediate is also pH dependent, suggesting amine dissociation in the ligand and formation of an unstable ligand radical leading to a final product with increased ligand unsaturation.
- Research Organization:
- Univ. of Notre Dame, IN
- OSTI ID:
- 6399438
- Journal Information:
- Inorg. Chem.; (United States), Vol. 20:5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HETEROCYCLIC COMPOUNDS
OXIDATION
RADIOLYSIS
NICKEL COMPLEXES
SODIUM BROMIDES
ANIONS
AQUEOUS SOLUTIONS
BROMINE
CHEMICAL REACTION KINETICS
ELECTRON TRANSFER
RADICALS
REACTION INTERMEDIATES
ALKALI METAL COMPOUNDS
BROMIDES
BROMINE COMPOUNDS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DECOMPOSITION
DISPERSIONS
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
HALOGENS
IONS
KINETICS
MIXTURES
NONMETALS
ORGANIC COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
REACTION KINETICS
SODIUM COMPOUNDS
SOLUTIONS
TRANSITION ELEMENT COMPLEXES
400600* - Radiation Chemistry