Synthesis, supramolecular structures and catalytic properties of nickel(II) 3-sulfobenzoate complexes with chelating amine ligands

Abstract

Five new Ni^II/3-sb/2,2′-bipy and Ni^II/3-sb/phen complexes, {[Ni(3-sb)(phen)(H₂O)₂]·H₂O}_n (1), [Ni(3-sb)(phen)₂(H₂O)]·H₂O (2), [Ni(phen)₃]·2(3-Hsb)·10H₂O (3), {[Ni(3-sb)(2,2′-bipy)(H₂O)₂]·H₂O}_n (4), and [Ni(2,2′-bipy)₃]₂·(3-Hsb)·3(NO₃)·9H₂O (5) [3-sb = 3-sulfobenzoate dianion; 2,2′-bipy = 2,2′-bipyridine; phen = 1,10-phenanthroline], have been synthesized and structurally characterized. The molecular structures of complexes 1 and 4 are 1-D polymers in which the 3-sb ligands bis-monodentately coordinate to the Ni^II ions. Complex 2 is a monomer. Complexes 3 and 5 are cation–anion species in which the 3-Hsb⁻ ligands are non-coordinating. These complexes containing interesting supramolecular assembly interactions: hydrogen-bonding interactions, π⋯π stacking interactions, and other weak interactions. The stability of complexes 3 and 5 from their TG analyses is higher than that of others, indicating that the host–guest assembly enhances the stability of the solid state. Interestingly, the catalytic experiments showed that complex 3 is the best catalyst among these nickel complexes for the oxidation reaction of methyl phenyl sulfide due to 3-D host–guest supramolecular assembly and stacking effects.