COMPLEXATION OF F-ELECTRON (3+) IONS WITH PSEUDOHALIDE LIGANDS

The coordination sphere of Nd(III) and Eu(III) cations in aqueous solu tions containing pseudohalide ligands has been studied by absorption s pectroscopy (hypersensitive transition) and luminescence lifetimes. It has been found that the tendency to form inner-sphere complexes incre ases in the order NCSe-<NCS-<N-3(-)<NCO-. The study of extraction of t etrahedral Co(II) complexes with NCS- and N-3(-) ligands has shown tha t the metal-bonded N-3(-) ligand interacts with water molecules much s tronger than the NCS- ligand. That explains why extraction of inner-sp here lanthanide complexes by TBP is much less efficient for the azide than for thiocyanate ligand, in spite of similar stability constants. (C) 1998 Elsevier Science S.A.