Use of an ion-exchange adduct of synthetic hectorite and chiral copper(II) complex as a packing material for chromatographic resolution

Abstract

A spherically shaped particle of synthetic hectorite (denoted as Na-HEC) was ion-exchanged with a divalent Cu(II) complex, [Cu(SS-oxa)]2+ (SS-oxa = SS-2,2′-isopropylidene-bis(4-phenyl-2-oxazoline)). The material is denoted as [Cu(SS-oxa)]2+/HEC. A column for high performance liquid chromatography (HPLC) was prepared by packing 4.0 g of [Cu(SS-oxa)]2+/HEC into a stainless tube (25 cm × 0.4 cm (i.d.)). When tris(acetylacetonato)cobalt(III) (denoted as [Co(acac)3]) was eluted by methanol at the flow rate of 0.2 mLmin−1 and 4 °C, the compound was separated to Δ- and Λ-enantiomers nearly to the baseline separation. Organic molecules with two hydroxyl groups such as 1,1′-binaphthyl-2,2′-diol were also resolved partially. The results promised the practical utility of the clay column chromatography for obtaining enantiomeric compounds.