Ester hydrolysis with 2,6-di(pyrazol-3-yl)pyridines and their CoII complexes in homogeneous and micellar media.
The 1:1 complex of Co(ClO4)2 with the H2O-insoluble tridentate 2,6-di(1H-4,5,6,7-tetrahydroindazol-3-yl)pyridine (H21) was found to be an excellent catalyst for the hydrolysis of para-nitrophenyl acetate in aqueous buffers over the pH 7.05-7.90 range, with an estimated second-order rate constant of 0.50 M(-1) s(-1). The Co2+ complexes of the N,N'-di-1-dodecyl analogue in micellar media and the N,N'-di-(4-carboxyphenyl) analogue in aqueous media were much poorer catalysts, poorer than the free ligands. In all cases, the pH-rate profiles indicated that free base, deprotonated or hydroxo forms were the active species. The greater success with Co(H(2)1)2+ indicated a catalytic role for N-H deprotonation.
Jairam
R
R
Department of Chemistry, York University, Toronto, Ontario, Canada.
Lau
M L
ML
Adorante
J
J
Potvin
P G
PG
D003035:Cobalt / Q000737:chemistry*; D004950:Esterases / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008823:Micelles; D011720:Pyrazoles / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*
D008823:Micelles; D011720:Pyrazoles; D011725:Pyridines; D003035:Cobalt; D004950:Esterases