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

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 kex (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.