Synthesis and Crystal Structure of Bis[2-(1,4,5,6-tetrahydropyrimidin-2-yl)phenolato]zinc(II)

Abstract

Magnetic dilution of coordination compounds, in which paramagnetic atoms in a crystal are partially substituted by diamagnetic atoms, is a useful technique to investigate the magnetic interactions in detail.1 To achieve magnetic dilution, it is necessarily to employ a diamagnetic metal ion with the same oxidation state and similar size to that of the original paramagnetic ion. Furthermore, the diamagnetic analogue of the desired complex has to be isomorphic. Since mononuclear cobalt(II) complexes can be a single-ion magnet,2,3 the preparation of a zinc(II) analogue is important. On the other hand, we recently reported that the bis[2-(1,4,5,6-tetrahydropyrimidin-2-yl)phenolato]cobalt(II) complex exhibits magnetic slow relaxation, even in the absence of an external magnetic field.3 It is suggested that the origin of the slow relaxation is to be intermolecular magnetic interactions induced by hydrogenbonding interactions. To investigate the effect of intermolecular interactions, we focused on the synthesis, crystal structure and hydrogen-bonded supramolecular structure of the zinc(II) analogue, bis[2-(1,4,5,6-tetrahydropyrimidin-2-yl)phenolato]zinc(II) (Fig. 1). The unsymmetrical bidentate ligand precursor, 2-(1,4,5,6tetrahydropyrimidin-2-yl)phenol (H2thp), was synthesized by a reported procedure.4 Although previously reported [Co(Hthp)2] was synthesized from the Co(BF4)2·6H2O, preparation of [Zn(Hthp)2] from the BF4 salt resulted in the formation of colorless microcrystals. Alternatively, colorless single crystals of [Zn(Hthp)2] were obtained by a reaction of ZnCl2, H2thp and KOtBu in a 1:2:2 ratio in ethanol. Yield: 34.1 mg (40%). Crystal data are included in Table 1. X-ray crystallographic 2019 © The Japan Society for Analytical Chemistry