Syntheses and structures of a phenoxo-bridged copper(II) distorted cubane and related complexes with 2-hydroxy-N-(2-pyridylalkyl)benzamide ligands

Two new pyridylalkylamide ligands containing phenol groups appended to the amide, 2-hydroxy-N-(2-pyridylmethyl)benzamide (HLPhOH) and 2-hydroxy-N-(2-pyridylethyl)benzamide (HLPhOH′), were synthesized. Copper(II) complexes of these ligands were synthesized and characterized by X-ray crystallography, ESI-MS, FTIR, UV/Vis, and EPR spectroscopy. When basic Et3N was used to deprotonate the ligands, tetracopper(II) [Cu4(LPhO)4] (1) or dicopper(II) [Cu2(LPhO′)2(CH3OH)2] (3) were formed. When base was not used, mononuclear [Cu(HLPhOH)2Cl2] (2) resulted. Complex 1 possesses a distorted cubane-like structure, with the ligands bridging via the phenoxo oxygen atoms, and the copper atoms possessing a distorted square planar geometry. The ligands in dimeric complex 3 also bridge between copper(II) atoms via the phenoxo oxygen atoms, and the copper atoms are square pyramidal. Monomeric 2 is a tetragonally distorted six-coordinate species with pyridyl N atoms and chloride ligands in the equatorial plane, and long interactions with the amide carbonyl O atoms in the axial positions.