Dinuclear formation, oxygen atom transfer, and intramolecular coordination isomerization in oxotechnetium complexes
Journal Article
·
· Inorganic Chemistry; (USA)
- Boston College, Chestnut Hill, MA (USA)
Dinuclear, asymmetric and dissymmetric, mixed-valent (III-IV), {mu}-oxo complexes of technetium spontaneously form in both neat pyridine and pyridine solutions in dichlorobenzene from higher valent, mononuclear species, with which they reach an equilibrium. When (OX{sub 4}Tc{sup V}){sup {minus}} is used as the starting material and only the neat pyridine ligand is present, the formation of the dinuclear species is second-order in Tc{sup V} and occurs with concomitant production of pyridine N-oxide, indicating that oxygen atom transfer occurs in the technetium reduction process. K{sub eq} for the formation of the dinuclear species in picoline solution is 193 {plus minus} 8 M{sup {minus}1} with k = (1.46 {plus minus} 0.1) {times} 10{sup {minus}2} M{sup {minus}1} s{sup {minus}1}. The asymmetric and dissymmetric dinuclear species spontaneously interconvert. In o-dichlorobenzene, this process is first-order in chloride ion and requires a minimum concentration ({approximately}0.1 M) of the pyridine ligand to prevent decomposition of the dinuclear starting material. With picoline as the ligand, at 140{degree}C the reaction proceeds with a specific rate of (3.12 {plus minus} 0.08) {times} 10{sup {minus}3} M{sup {minus}1} s{sup {minus}1} to approach an equilibrium between the asymmetric and dissymmetric complexes with K{sub eq} = 2.83 {plus minus} 0.12. Activation parameters are {Delta}H* = 144 {plus minus} 2 kJ/mol and {Delta}S* = 53.5 {plus minus} 1 J/(mol K). Minor changes in the ligands generate marked differences in K{sub eq} and K{sub iso}.
- OSTI ID:
- 5305602
- Journal Information:
- Inorganic Chemistry; (USA), Journal Name: Inorganic Chemistry; (USA) Vol. 27:26; ISSN 0020-1669; ISSN INOCA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400200* -- Inorganic
Organic
& Physical Chemistry
AROMATICS
AZINES
BENZENE
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL STATE
COMPLEXES
EQUILIBRIUM
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
ISOMERIZATION
KINETICS
LIGANDS
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
OXYGEN COMPOUNDS
PYRIDINES
REACTION KINETICS
STRUCTURAL CHEMICAL ANALYSIS
TECHNETIUM COMPLEXES
THERMODYNAMIC ACTIVITY
TRANSITION ELEMENT COMPLEXES
400200* -- Inorganic
Organic
& Physical Chemistry
AROMATICS
AZINES
BENZENE
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL STATE
COMPLEXES
EQUILIBRIUM
HETEROCYCLIC COMPOUNDS
HYDROCARBONS
ISOMERIZATION
KINETICS
LIGANDS
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
OXYGEN COMPOUNDS
PYRIDINES
REACTION KINETICS
STRUCTURAL CHEMICAL ANALYSIS
TECHNETIUM COMPLEXES
THERMODYNAMIC ACTIVITY
TRANSITION ELEMENT COMPLEXES