Hydrolysis of 8-Quinolyl Phosphate Monoester: Kinetic and Theoretical Studies of the Effect of Lanthanide Ions

8-Quinolyl phosphate (8QP) in the presence of the trivalent lanthanide ions (Ln = La, Sm, Eu, Tb, and Er) forms a [Ln center dot 8QP](+) complex where the lanthanide ion catalyzes hydrolysis of 8QP. In reactions with Tb3+ or Er3+, there is evidence of limited intervention by a second lanthanide ion. Rate constants are increased by more than 10(7)-fold, and kinetic data and B3LYP/ECP calculations indicate that the effects are largely driven by leaving group and metaphosphate ion stabilization. The lanthanides favor a single-step D(N)A(N) mechanism with a dissociative transition state, with limited nucleophilic assistance, consistent with the low hydroxide ion dependence and the small kinetic effect of Ln(3+) radii.