Chain of water hexamers and tetramers hosted in a redox product of a Co(III) metal complex: Syntheses, characterization and single crystal X-ray structure determination of Co(II/III) complexes with sulfur oxo-anions

In the present study, four new Co(II/III) metal complexes, [Co(phen)3]S4O6·2H2O (1), [Co(phen)3]S4O6·7H2O (2), [Co(phen)3]2(S4O6)3·6.5H2O (3) and [Co(phen)3]S2O3·9H2O (4), have been synthesized and characterized by elemental analysis, TGA and various spectroscopic techniques. In the case of 1 and 2, an unexpected redox reaction took place and the complexes formed are different in terms of their water of crystallization. The structures of 1–3 have been determined by single crystal X-ray crystallography. Complex salts 1–3 crystallize in the orthorhombic (Pbca  ), triclinic (P1¯) and monoclinic (P21/c) crystal systems, respectively. Their X-ray crystal structure determination revealed the presence of non-covalent cation-to-anion (C–H⋯Oanion hydrogen bonds), anion-to-cation (anion⋯π interactions) and cation-to-cation (C–H⋯π and π⋯π stacking interactions) interactions. Interestingly, a detailed packing analysis has shown the presence of rare chains of cyclic water hexamers (chair form) and tetramers, stabilized by O–H⋯O and C–H⋯O hydrogen bond interactions in the supramolecular complex [Co(phen)3]S4O6·7H2O (2).

Four new Co(II/III) complexes containing sulfur oxo-anions have been synthesized and characterized by TGA, spectroscopic techniques and X-ray crystallography. Packing analysis has revealed the presence of rare chains of water hexamers and tetramers in [Co(phen)3]S4O6·7H2O. This paper also presents the first structural report of the redox products [Co(phen)3]S4O6·xH2O, where x = 2/7.Figure optionsDownload as PowerPoint slideHighlights
► Rare chains of water hexamers and tetramers have been observed.
► First structural report of the redox products [Co(phen)3]S4O6·xH2O, x = 2/7.
► Four new Co(II/III) complex salts with sulfur oxo-anions have been synthesized.
► Non-covalent interactions play as crucial role in lattice stabilization.