New complexes of tris(2-aminoethanolato-O,N)cobalt(III) sulfates: Synthesis and structure

The reaction of [Co(Etm)3] · 3H2O (I) with sulfuric acid affords [Co(HEtm)3]2(SO4)3 · 4H2O (II). The change in the synthesis procedure (the direction interaction of cobalt(II) sulfate with β-aminoethanol (HEtm)) makes it possible to isolate [Co(HEtm)3](SO4)(HSO4) · H2O (III) and {[Co(HEtm)3][Co(Etm)3]}2(SO4)3 · 7.75H2O (IV). The X-ray diffraction analyses of compounds II–IV show that all of them are of the ionic type. In compounds II and III, the ionic structure consists of the [Co(HEtm)3]3+ cations and sulfate anions in a ratio of 2: 3 and 1: 2, respectively. The basic difference in compounds II and III is the different degrees of deprotonation of the acid residues. In complex II, two anions SO42− are doubly deprotonated. In complex III, of the four anions found in the independent part of the unit cell of the sulfate anion two anions are monodeprotonated. In structure IV, two crystallographically independent complexes [Co(HEtm)3]3+ and [Co(Etm)3] are joined into a dimer through the O-H⋯O hydrogen bonding.