The coordination and extractive chemistry of the later 3d transition metals with bis((1R-benzimidazol-2-yl)methyl)sulfide

Abstract

The coordination chemistry of the later 3d metal ions with bis((1H-benzimidazol-2-yl)methyl)sulfide (NSN) is investigated. All the complexes had general formula [M(NSN)₂]X yH₂O, where M = Co(II), Ni(II), Cu(II), and Zn(II), ) or , and y = 2–5. The infrared and conductivity measurements provided evidence that the sulfate and sulfonate acted as counter anions in the isolation of these dicationic complexes. X-ray crystal structures of [Co(NSN)₂](RSO₃)₂ 4H₂O and [Ni(NSN)₂](RSO₃)₂ 2H₂O revealed a distorted octahedral geometry for these complexes. Extraction studies showed a lack of pH-metric separation of the later 3d metal ions with bis((1-octylbenzimidazol-2-yl)methyl)sulfide (BONSN) as an extractant, but that extractions occurred in the low pH range with an opportunity for back-extraction. This investigation suggests that tridentate ligands (of the nature investigated) are not feasible extractants for metal ions due to their lack of stereochemical “tailor making.”

Keywords:

• Base metals
• Bis((1H-benzimidazol-2-yl)methyl)sulfide
• Tridentate
• Extractive and coordination chemistry

Acknowledgments

The authors thank Mr. F. Chindeka (DST/Mintek-NIC, Rhodes University Chemistry Department) for the microanalysis results. We would also like to thank Shell Chemicals (SA) (Pty) Ltd. for supplying Shellsol 2325. For financial support, we thank the National Research Foundation (NRF-CPR20100406000010238).