A preparative and phosphorus-31 nuclear magnetic resonance study of the coordination of three phosphate based ligands to dioxouranium(VI)

Abstract

The three species [UO₂{OP(OMe)(NMe₂)₂}₄](ClO₄)₂, [UO₂{OP(OMe)₂(NMe)}5] (C1O₄)₂ and [UO₂{OPMe₂Ph)]₅] (ClO₄)₂ have been isolated and their CD₂Cl₂ solutions studied by means of ³¹P n.m.r. An equilibrium between [UO₂L₅²⁺ and [UO₂L₄]²⁺ exists in solutions of the first two species. In solutions of the third species [UO₂L₅]²⁺ predominates and ligand exchange proceeds through a dissociative D mechanism for which k_ex (285 K), characterizing a single ligand, is 1830 ± 250 s^-1, ΔH^‡ 82.15 ± 1.8 kJ mol^-1 and ΔS^‡ 106 ± 16 JK^-1 mol^-1.