Syntheses and crystal structures of metal (Mn, Co, Ni) chloride complexes with 3-hydroxypyridin-2-one and contribution of O[sbnd]H⋯Cl hydrogen bonds to their structural diversity

Abstract

Reactions of MCl2·nH2O (M = Mn, Co, Ni) and 3-hydroxypyridin-2-one (dhpyH2 = C5H5NO2) afforded novel molecular complexes [MCl2(dhpyH2)4] (M = Mn (1), Co (3)) and binuclear [Co2Cl2(µ-Cl)2(dhpyH2)2(MeCN)2] (4), as well as ionic complexes [M(dhpyH2)4(ROH)2]Cl2·2ROH (R = Et, M = Co (6), Ni (8); R = Me, M = Ni (9)), and [Ni(dhpyH2)4(MeOH)2]Cl2 (10). In addition, two cocrystals, namely [MCl2(dhpyH2)4][M(dhpyH2)4L2]Cl2·S, (M = Mn, L = H2O, S = 4THF (2), M = Co, L = MeOH, S = 2MeOH (5)) were prepared. Single crystal X-ray analyses reveal two modes of 3-hydroxypyridin-2-one ligation; a chelate coordination to central cobalt ion in binuclear complex 4 and a monodentate coordination in complexes 1–3, 5, 6, 8–10. The monodentate coordination of four 3-hydroxypyridin-2-one molecules to central ion is favored due to the stabilization by strong intramolecular hydrogen bonds and formation of a macrocycle resembling 16-membered crown ethers. Coordination modes of 3-hydroxypyridin-2-one, ancillary ligands and solvate molecules determine connectivity patterns in crystal structures. Various hydrogen-bonding motifs and off-center parallel stacking arrangements of coordinated 3-hydroxypyridin-2-one molecules result in layered (4, 6, 8, 9) and 3D structures (1–3, 5, 10). Coordinated or free chloride ions are in some complexes the only (and in other complexes, prevailing) acceptors of intermolecular hydrogen bonds. A variety of D–H⋯Cl (D = O, N) geometries of hydrogen bonds in complexes is investigated. Chloride ions are in the majority of these complexes concomitantly engaged as acceptors in two hydrogen bonds, if coordinated to metal ions, and in three hydrogen bonds, if not ligated.