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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

Journal Article · · Inorg. Chem.; (United States)
DOI:https://doi.org/10.1021/ic50219a026· OSTI ID:6399438
;
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), Journal Name: Inorg. Chem.; (United States) Vol. 20:5; ISSN INOCA
Country of Publication:
United States
Language:
English

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Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ALKALI METAL COMPOUNDS
ANIONS
AQUEOUS SOLUTIONS
BROMIDES
BROMINE
BROMINE COMPOUNDS
CHARGED PARTICLES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DECOMPOSITION
DISPERSIONS
ELECTRON TRANSFER
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
HALOGENS
HETEROCYCLIC COMPOUNDS
IONS
KINETICS
MIXTURES
NICKEL COMPLEXES
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION INTERMEDIATES
REACTION KINETICS
SODIUM BROMIDES
SODIUM COMPOUNDS
SOLUTIONS
TRANSITION ELEMENT COMPLEXES