Synthesis and electronic properties of transition metal complexes containing sulfonamidoquinoline ligands

Abstract

The coordination chemistry of 4-nitro-N-(quinolin-8-yl)benzenesulfonamide has been expanded. Crystal structures of bis[4-nitro-N-(quinolin-8-yl)benzenesulfonamidato-κ2N,N′]cobalt(II) (2), diaqua-bis[4-nitro-N-(quinolin-8-yl)benzenesulfonamidato-κ2N,N′]nickel(II) (3), and bis[4-nitro-N-(quinolin-8-yl)benzenesulfonamidato-κ2N,N′]zinc(II) (4) containing this ligand in ML2 stoichiometry were obtained. The nickel complex is isolated as a dihydrate. The degree of tetrahedrality for the four coordinate copper, cobalt, and zinc complexes was quantitatively compared by calculating the τ4 geometric parameters. Zinc complex 4 was found to be the most tetrahedral, while copper complex 1-NO2 deviated most from tetrahedral geometry. The magnetic moment calculated for 1-NO2 showed inconsistencies when measured in solution and in the solid state. Only a Cu+2 center exists in solution, while a possible mixed spin state of Cu+2 and Cu+3 is proposed in the solid state. With a more electron releasing substituent on the ligand of the copper complex as seen in complex 1-Me, this behavior is not observed and Cu+2 exists in solution and solid state. A reversible reduction at the same potential (−1.5 V vs. ferrocene) for both the ligand and the complex suggests possible redox activity of this class of ligand.