SOLUTION EQUILIBRIA AND KINETIC-STUDIES OF THE COPPER(II) PROMOTED HYDROLYSIS OF 8-QUINOLYL PHOSPHATE - A LARGE RATE ENHANCEMENT FOR THE HYDROLYSIS OF A PHOSPHATE MONOESTER DIANION

The dissociation constants of 8-quinolyl phosphate (H3L+) at 10°C and I = 0.1 mol dm−3 (NaCIO4) have been determined (pKavalues <1.5, 4.12 and 6.46). At a 1:1 ligand to metal ratio, the interaction of copper(II) with 8-quinolyl phosphate can be described by the equilibria given below. Cu2+ + H++ L2- ⇌ [CuHL]+log β111 = 9.13(3) Cu2++ L2- ⇌ [CuL]° log β110= 5.38(1) Cu2++ H2O + L2- ⇌[CuL(OH)]−+ H+log β11-1= −0.33(3) The pKa values for the ionisation processes [CuHL]+⇌ [CuL] + H +and [CuL(OH2)]⇌ [CuL(OH)]−+ H+are 3.75 and 5.71, respectively. Kinetic studies establish that in the copper(II)-promoted hydrolysis the complex [CuL] is the active species with kCuL= 2.7 × 10_3s_1at 30°C and I = 0.1 moldm−3. Copper(II) ions promote the hydrolysis of the normally unreactive dianion L2-of the phosphate monoester by a factor of ca 106. © 1991, Taylor & Francis Group, LLC. All rights reserved.