ZIRCONIUM AND HAFNIUM MIXED-LIGAND COMPLEXES WITH ETHYLENEDIAMINETETRAACETATE, FLUORINE AND CARBONATE IONS. Vadim E. Mistrioukov, Yuri N. Mikhailov, Elena B. Chuklanova, Alexander V.Sergeev, Kurnakov's Institute of General and Inorganic Chemistry of Russian Academy of Sciences.
Zirconium(IV) and hafnium(IV) form with ethylene-diaminetetraacetate ion together with fluorine or carbonate ions 8 coordinated complex anions. Complexone, fluorine and carbonate ions can form separately stable complexes with Zr(IV) and Hf(IV), so mixed ligand complex formation was hard to predict.
(CN3H6)2[Zr(edta)F2]1.5H2 (A), (CN3H6)2[Hf(edta)F2]H2O (B) (CN3H6)2[Zr(edta)CO3]3H2O(C) and (CN3H6)2[Hf(edta)CO3]3H2O (D) were obtained from [Me(edta)(H2O)2] intermediate by adding fluorine or carbonate ions. Isolated transparent crystals do not hydrolyse in aqueous solution - that is rare phenomena for Zr and Hf - and may be recrystallized without their composition change.
Edta4- -ion in compounds A - D has closed configuration which could be described as E,G/R. In (CN3H6)2[Zr(edta)F2]1.5H2 and (CN3H6)2[Hf(edta)F2]H2O oxygen atoms of R-glycine cycles of edta-ion have longer distances to central atom then O atoms of G-glycine cycles, two distances from Zr to N atoms are equal, so as from Hf to N. But in Hf complexes Me-N distances are shorter. The main distinction between Zr and Hf complexes is coordinated F-ions participance in H-bonds.
When F ions in complexes A and B are changed to carbonate ion and complexes C and D are obtained, all oxygen atoms of glycine cycles occurs to have same distances to central atom.