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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 16, Number 7
BKCSDE 16(7)
July 20, 1995 

Mechanistic Studies on the Oxidation of Triphenylphosphine by [(tpy)(bpy)RuⅣ=O]2+, Structure of the Parent Complex [(tpy)(bpy))RuⅡ-OH2]2+
Won Kyung Seok*, Mee Yung Kim, Yoshinobu Yokomori, Derek J. Hodgson, Thomas J. Meyer*
Oxidation of triphenylphosphine to triphenylphosphine oxide by [(tpy)(bpy)Ru(O)]2+ (tpy is 2,2':6',2"-terpyridine and bpy is 2,2'-bipyridine) in CH3CN has been studied. Experiments with the 18O-labeled oxo complex show that transfer of oxygen from [(tpy)(bpy)RuⅣ =O]2+ to triphenylphosphine is quantitative within experimental error. The reaction is first order in each reactant with k (25.3 ℃)=1.25 × 106 M-1s-1. The inital product, [(tpy)(bpy)RuⅡ-OPPh3]2+, is formed as an observable intermediate and undergoes slow k (25 ℃)=6.7 × 10-5 s-1 solvolysis. Activation parameters for the oxidation step are ΔH≠=3.5 kcal/mol and ΔS≠ =-23 eu. The geometry at ruthenium in the complex cation, [(tpy)(bpy)RuⅡ(OH2)]2+, is approximately octahedral with the ligating atoms being the three N atoms of the tpy ligand, the two N atoms of the bpy ligand, and the oxygen atom of the aqua ligand. The Ru-O bond length is 2.136(5) Å.
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