In aqueous solutions at 80 degrees C, [RuClCp(mPTA)(2)](OSO2CF3)(2) (1) and [RuCp(mPTA)(2)(OH2 kappa O)1(OSO2CF3)(3)center dot(H2O)(C4H10O)(0.5) (3) (mPTA: N-methyl-PTA) were found effective catalysts of the redox isomerization of alk-1-en-3-ols to the corresponding ketones, characterized by initial turnover frequencies (TOF) of 162 h(-1) (3) and 9.6 h(-1) (1) in 1-octen-3-ol isomerization. A sharp maximum of the reaction rate as a function of pH was observed with 1 in phosphate buffer solutions. Kinetic and P-31 NMR measurements revealed for the first time in aqueous organometallic catalysis that component(s) of phosphate buffer (most probably HPO42-) strongly interact(s) with the catalyst complexes and this interaction leads to a dramatic loss of the catalytic activity. (C) 2010 Elsevier B.V. All rights reserved.