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Zirconium( IV ) Complexes of Oxydiacetic Acid in Aqueous Solution and in the Solid State as Studied by Multinuclear NMR and X‐ray Crystallography
Author(s) -
Ma Weiwen,
van Koningsveld Henk,
Peters Joop A.,
Maschmeyer Thomas
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010202)7:3<657::aid-chem657>3.0.co;2-6
Subject(s) - carboxylate , crystallography , zirconium , chemistry , aqueous solution , crystal structure , nuclear magnetic resonance spectroscopy , nmr spectra database , ether , stereochemistry , inorganic chemistry , spectral line , physics , organic chemistry , astronomy
The structures of complexes of Zr IV and oxydiacetate (ODA 2− ) in aqueous solutions of pH 0–7 were investigated with the use of 1 H, 13 C, and 17 O NMR spectroscopy. Equilibria of mononuclear [Zr(oda)] 2+ , [Zr(oda) 2 ], and [Zr(oda) 3 ] 2− complexes have been observed. In all complexes ODA 2− is bound in a tridentate fashion through the two carboxylate groups and the ether oxygen. No di‐ or oligonuclear species containing ODA 2− were observed. An excess of free Zr IV remains in solution, probably as a result of weak electrostatic interactions between negatively charged Zr–ODA complexes or free ODA 2− and a positively charged cyclic tetranuclear hydroxy zirconium complex. CP‐MAS 13 C NMR spectra of solid compounds isolated from the samples indicated that the structures of the [Zr(oda) 2 ] and [Zr(oda) 3 ] 2− complexes in solution are similar to those in the solid state. This is corroborated by the single‐crystal X‐ray structure of Na 2 [Zr(oda) 3 ] ⋅ 5.5 H 2 O, which was obtained from a solution containing exclusively the [Zr(oda) 3 ] 2− complex. In this structure Zr IV is nine‐coordinate with the three ODA 2− ligands bound in a tricapped trigonal prismatic geometry. The negative charge of this [Zr(oda) 3 ] 2− complex is balanced by two Na + ions, one of which is on a center of symmetry between Δ and Λ enantiomers of [Zr(oda) 3 ] 2− . This Na + is octahedrally coordinated to six (non Zr IV ‐bound) carboxylate oxygen atoms of six different [Zr(oda) 3 ] 2− units.