Crystallographic determination of three ni-α-hydroxyoxime-carboxylic acid synergist complexes

X-ray crystal structures of three dicarboxylato-bis-α-hydroxyoximenickel(II) complexes have been obtained. These contain a short chained (C8) analogue of LIX<sup/> 63 hydroxyoxime, along with either benzoate, isobutyrate or propionate. All have pseudo-octahedral structures with monodentate carboxylate anions located cis to one another and neutral, chelating α-hydroxyoxime ligands. Intra-molecular hydrogen bonding between each anionic acid's carboxylate group and an adjacent oxime hydroxyl group is evident. Inter-molecular hydrogen bonding is also observed. These provide the first definitive structural elucidation of the types of nickel complexes that could be formed during synergistic extraction by LIX® 63 and carboxylic acids. © Taylor & Francis Group, LLC.