Ligand chirality-controlled selective formation of mono- and dinuclear copper complexes

Reaction of copper(II) acetate with the (S)-enantiomer of a tridentate binaphthyl Schiff base ligand, 2-(3,5-dichloro-2-hydroxybenzylideneamino)-2′-hydroxy-1,1′-binaphthyl (H2L), in methanol afforded mononuclear copper(II) complex [CuII(HL)2] ((S,S)-1) in 52% isolated yield. The same reaction gave dinuclear copper(II) complex [CuII2(L)2] ((R,S)-2) in 73% isolated yield when racemic-H2L was used instead of (S)-H2L. Both complexes (S,S)-1 and (R,S)-2 were characterized by elemental analysis, mass spectrometry, and X-ray crystallography. The present work highlights the functioning of ligand chirality as a ‘switch’ for selective formation of mono- and dinuclear metal complexes.