Highly selective extraction of Cu(II) and Zn(II) using [B(3-iPrpz)(4)](-) (iPrpz = isopropylpyrazolyl)

摘要

The solvent extraction of first-series transition metal ions {n(II), Fe(II), Co(II), Ni(II), Cu(II) and Zn(Il)}with [B(3-iPrpz)4](-)(iPrpz = isopropylpyrazolyl) is reported. Although the previously reported tetrakis(pyrazolyl)borates, [B(PZ)(4)](-) and [B(3-Mepz)(4)](-), quantitatively extracted all the studied transition metal ions, [B(3-iPrpZ)(4)](-) extracted only Cu(II) and Zn(II). In order to elucidate the origin of the selectivity, the structures of the extracted species, [B(3-iPrPZ)(4)](2)Zn (1) and [B(3-iPrpZ)(4)]Cu(OCOCH3) (2), were determined by single-crystal X-ray diffraction. Complex 1 has a tetrahedral geometry with each ligand having bidentate coordination. Complex 2 has a distorted square pyramidal geometry with [B(3-iPrpz)(4)](-) having tridentate coordination and the acetate anion having asymmetric bidentate coordination. These structures of the extracted species are different from those of the previously studied tetrakis(pyrazolyl)borates, which are octahedral A(2)M with each ligand having tridentate coordination (A(-) = tetrakis(pyrazolyl)borate, M2+ = first-series transition metal ion). Because the bulky isopropyl groups at the 3-position of the pyrazolyl ring prevent octahedral geometry, the other metal ions cannot form stable and extractable complexes with [B(3-iPrpZ)(4)](-). (C) 2003 Elsevier Ltd. All rights reserved.