N , S -donor acetamide ligand: silver (I) binding and test silver (I) extraction studies
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N,S‑donor acetamide ligand: silver (I) binding and test silver (I) extraction studies Abiodun D. Aderibigbe1,2 · Andrew J. Clark1 Received: 5 August 2020 / Accepted: 19 September 2020 © Springer Nature Switzerland AG 2020
Abstract Ligands bearing soft donors including N- and S- have found applications in selective metal recovery due to the ability to preferentially bind soft acceptors like Ag+. Herein, N-(2-((4-vinylbenzyl)thio)ethyl)acetamide (L) bearing potential Ag+-selective N- and S-donors was prepared in a 76% yield under mild conditions. Reaction of L with silver perchlorate and silver nitrate gave complexes 1 and 2, as pastes, in yields of 98 and 77%, respectively. Physico-chemical and spectroscopic characterizations confirmed the chemical compositions of L, 1 and 2. ESI–MS data indicated that 1 and 2 each contain both the [AgL]+ and [AgL2]+ types complexes. Binding studies carried out by Job plot and 1H NMR titration using silver perchlorate indicated that L interacts with A g+ to form the [AgL]+ type complex and that the N- and S-donors may be + responsible for binding A g . Finally, L was observed to demonstrate excellent selectivity and moderate efficiency (36%) for Ag+ extraction from an aqueous solution also containing Cu2+ and Pb2+.
Introduction To date, much research interest has been paid to the syntheses of ligands bearing soft donors like N- and S- due to the promising use for the recovery of silver [1, 2]. The uniqueness of these ligands lies in the ability to selectively bind Ag+ according to the hard/soft acid/base rule [3]. In addition to the softness property, the structure of the ligand and number of donors present determines the effectiveness for selective Ag+ binding [4, 5]. Therefore, synthetic chemists continue to concentrate research efforts into ligand design. For example, Inoue’s group [1] showed that increasing the length of the oxyethylene arms placed near the N-donors in a range of tridentate cyclotriphosphazene ligands triggered increase in the Ag+ extraction efficiency. More importantly,
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11243-020-00428-2) contains supplementary material, which is available to authorized users. * Abiodun D. Aderibigbe [email protected] 1
Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
Department of Chemistry, Federal University of Technology Akure, P.M.B. 704, Akure, Ondo state, Nigeria
2
the oxyethylene arms were stationed near the N-donor ensuring cooperativity in Ag+ binding and a relatively stable complex. Binding studies carried out by solvent extraction and 1 H NMR characterization revealed that the cyclotriphosphazene formed a [AgP]+ type complex (where P represents the cyclotriphosphazene ligand) with a square pyramidal geometry. Recently, Daubinet and Kaye [4] demonstrated the importance of providing appropriate spacer groups between donors towards achieving high selectivity and efficiency in Ag+ extraction. They designed and sy
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