Instability of the oxidation catalysts ((bpy)/sub 2/(py)Ru(O))/sup 2 +/ and ((trpy)(phen)Ru(O))/sup 2 +/in basic solution

Journal Article · Wed Nov 06 04:00:00 EST 1985 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00217a018· OSTI ID:5896240

Roecker, L; Kutner, W; Gilbert, J A; Simmons, M; Murray, R W; Meyer, T J

The Ru(IV) complexes ((bpy)/sub 2/(py)Ru(O))/sup 2 +/ (1) and ((trpy)(phen)Ru(O))/sup 2 +/ (2) (bpy = 2,2'-bipyridine, py = pyridine, trpy = 2,2',2''-terpyridine, and phen = 1,10-phenanthroline) are unstable toward self-reduction in basic solution. Product analyses, performed by using UV-vis spectroscopy, cyclic voltammetry, HPLC, and GC, show that O/sub 2/ is not a product of the self-reductive chemistry and that ca. 80% of the reduced products that appear are the unmodified polypyridyl complexes of Ru(II), ((bpy)/sub 2/(py)Ru(OH))/sup +/ or ((trpy)(phen)Ru(OH))/sup +/. The remaining 20% of the products are accounted for by at least four different products, which are also Ru(II) but appear to have undergone varying degrees of ligand oxidation. Kinetic studies were performed with stopped-flow or conventional mixing techniques. For complex 2, plots of log absolute value A/sub infinity/ - A/sub t/ vs. time were linear from pH 12 to 14 and the experimental rate law can be described by -d(Ru(IV))/dt = k/sub a/ (OH/sup -/)/sup 2/, where k/sub a/ = 0.21 +/- 0.01 M/sup -1/ s/sup -1/ and k/sub b/ = 0.08 +/- 0.02 M/sup -2/ s/sup -1/ at 25/sup 0/C and ..mu.. = 1.0 M (Na/sub 2/SO/sub 4/). For the k/sub a/ path ..delta..H = 12 +/- 2 kcal/mol and ..delta..S = -20 +/- 6 eu. For complex 1, plots of log absolute value A/sub infinity - A/sub t/ vs. time were not linear but could be resolved into two successive components to yield rate constants for the self-reduction of Ru(IV) and, following that, of Ru(III). 17 references, 11 figures, 3 tables.

• Research Organization: Univ. of North Carolina, Chapel Hill
• OSTI ID: 5896240
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 24:23; ISSN INOCA
• Country of Publication: United States
• Language: English

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ABSORPTION SPECTROSCOPY
AROMATICS
AZAARENES
AZINES
CATALYSTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHROMATOGRAPHY
COMPLEXES
DATA
DECOMPOSITION
DISPERSIONS
EXPERIMENTAL DATA
GAS CHROMATOGRAPHY
HETEROCYCLIC COMPOUNDS
INFORMATION
KINETICS
LIGANDS
LIQUID COLUMN CHROMATOGRAPHY
MIXING
MIXTURES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
PH VALUE
PHENANTHROLINES
PHYSICAL PROPERTIES
PYRIDINES
REACTION KINETICS
REDUCTION
RUTHENIUM COMPLEXES
SEPARATION PROCESSES
SOLUTIONS
SPECTRA
SPECTROSCOPY
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPLEXES
ULTRAVIOLET SPECTRA
VALENCE
VOLTAMETRY
YIELDS