Chemical kinetics of nickel(III) macrocyclic complexes. Pulse radiolysis study of Ni/sup II/(CR+4H), Ni/sup II/(CR), and Ni/sup II/(CR-2H) in aqueous solutions of Br/sup -/ and CNS/sup -/. [Gamma radiation]
Oxidation of three closely related nickel (II) macrocyclic complexes Ni/sup II/(CR-2H), Ni/sup II/(CR), and Ni/sup II/(CR+4H) via anion radical reaction has been investigated by pulse radiolysis methods. While the initial oxidation products follow the form Ni/sup III/(L)(X/sup -/)(H/sub 2/O), in agreement with previous studies (L = macrocyclic ligand; X/sup -/ = Br/sup -/, SCN/sup -/), pH- and anion-concentration-dependent behavior provides evidence indicating subsequent formation of several other complexes Ni/sup III/(L)(X/sup -/)/sub 2/, Ni/sup III/(L)(OH/sup -/)(H/sub 2/O), Ni/sup III/(L)(OH/sup -/), and Ni/sup III/(L)(OH/sup -/)/sub 2/. The kinetics for interconversion among these species have been measured and are found in several cases to exhibit reversible behavior. In those cases the associated equilibrium constants have been determined. The formation of Ni/sup III/(L)(X/sup -/)/sub 2/ may be seen to depend on the degree of macrocyclic unsaturation and character of the anion. With the exception of the fully unsaturated CR-2H ligand, Ni/sup III/(L)(OH/sup -/) and Ni/sup III/(L)(OH/sup -/)(H/sub 2/O) and Ni/sup III/(L)(OH/sup -/)/sub 2/ decay via ligand radical formation at neutral pH and higher. Steady-state radiolysis results indicate introduction of an additional double bond into the ligand. At low pH, anion-substituted Ni(III) species return almost quantitatively to their parent Ni(II) complexes.
- Research Organization:
- Univ. of Notre Dame, IN
- OSTI ID:
- 5192778
- Journal Information:
- Inorg. Chem.; (United States), Vol. 21:5
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BROMIDES
CHEMICAL REACTIONS
HETEROCYCLIC COMPOUNDS
OXIDATION
HYDROXYL RADICALS
NICKEL COMPLEXES
THIOCYANATES
WATER
RADIOLYSIS
AQUEOUS SOLUTIONS
CHEMICAL REACTION KINETICS
EXPERIMENTAL DATA
LIGANDS
PH VALUE
REACTION INTERMEDIATES
ANTITHYROID DRUGS
BROMINE COMPOUNDS
CARBONIC ACID DERIVATIVES
CHEMICAL RADIATION EFFECTS
CHEMISTRY
COMPLEXES
DATA
DECOMPOSITION
DISPERSIONS
DRUGS
HALIDES
HALOGEN COMPOUNDS
HORMONE ANTAGONISTS
HYDROGEN COMPOUNDS
INFORMATION
KINETICS
MIXTURES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
REACTION KINETICS
SOLUTIONS
TRANSITION ELEMENT COMPLEXES
400600* - Radiation Chemistry
400201 - Chemical & Physicochemical Properties
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)