Autoxidation of binuclear ruthenium(II) ammines

Journal Article · Wed Jul 06 00:00:00 EDT 1983 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00156a009· OSTI ID:5273027

Stanbury, D M; Gaswick, D; Brown, G M; Taube, H

The reduction of oxygen to hydrogen peroxide by a series of binuclear ruthenium(II) ammines has been studied in acidic aqueous solution. The complex ((Ru(NH/sub 3/)/sub 5/)/sub 2/L)/sup 4 +/, where L = BPDO = meso-4,5-bis(4-pyridyl)-2,2-dimethyl-1,3-dioxolane, was studied in greatest detail. BPDO has a geometry such as to force the two ruthenium centers into close proximity. The kinetics of the autoxidation of the BPDO binuclear complex, as measured by the decay of the charge-transfer band characteristic of ruthenium(II) pyridyl type complexes, showed biphasic behavior. The first phase corresponds to the pseudo-first-order reaction of the full reduced complex, while the second phase corresponds to the reaction of the mixed-valence species. Inhibition of the second phase by Ru(III) at higher pH is taken as evidence that the mechanism involves outer-sphere electron transfer to form free superoxide. Subsequent protonation of superoxide and reduction to hydrogen peroxide complete the reaction. By comparison of the rates and expected steric and electrostatic effects, it is argued that the mechanism of the first phase likewise has a rate-limiting step involving outer-sphere generation of superoxide.

• Research Organization: Stanford Univ., CA
• OSTI ID: 5273027
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 22:14; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
AMMINES
AQUEOUS SOLUTIONS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COMPLEXES
DISPERSIONS
KINETICS
MIXTURES
OXIDATION
PH VALUE
REACTION KINETICS
RUTHENIUM COMPLEXES
SOLUTIONS
TRANSITION ELEMENT COMPLEXES