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Nuclear magnetic resonance study of praseodymium europium ytterbium ethylenediaminetetraacetates

1978; Elsevier BV; Volume: 30; Linguagem: Inglês

10.1016/s0020-1693(00)89018-0

1873-3255

Rosalind V. Southwood-Jones, André E. Merbach,

Coordination Chemistry and Organometallics

Proton NMR has been used to study the structural and kinetic behaviour in D20 solution, of the ethylenediaminetetraacetates of praseodymium, europium and ytterbium. The constants KHLnEDTA− for the following equilibrium have been measured LnOH(EDTA)H2O)2−n−1 + H+ ⇌ Ln(EDTA)(H2O)−n (log KHLnEDTA− = 12.86 (Pr), 12.48 (Eu) and 12.3 (Yb) at 20 °C). In the case of ytterbium the rate of interconversion of YbEDTA− the hydroxo complex has been estimated, and is of the order of 104 sec−1. Finally, evidence has been given for the existence of 1:2 2:3 complexes in a solution of europium with an excess of EDTA; in the 1:2 complex the second EDTA molecule is bound by only one iminodiacetate group whereas in the 2:3 complex one EDTA molecule acts as a bridging ligand.