Extraction behavior of trivalent metal ions into an ionic liquid with 2-mercaptopyridin -oxide

Eguchi, Ayano ; Morita, Kotaro*; Okamura, Hiroyuki   ; Hirayama, Naoki*

2-Mercaptopyridine -oxide (HSPyO) is a bidentate ligand with a hard O-donor and a soft S-donor. This ligand is expected to be effective in an ionic liquid (IL) chelate extraction because of its high solubility in ILs. In this study, we investigated the IL chelate extraction behavior of Al(III), Ga(III), and In(III) into ILs, 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imides ([Cmim][TfN], n = 2, 4, 8), using HSPyO as an extractant. The extraction selectivity order was In(III) Ga(III), whereas Al(III) was not extracted. Therefore, HSPyO was favorable for the extraction of soft In(III). The extractability order for solvents was ILs chloroform in the Ga(III) extraction, indicating that ILs exhibit high extraction performance. In addition, it was implied that the extracted species were the neutral complexes, M(SPyO), for all metals.