Structural and Magnetic Properties of Monomeric and Dimeric Copper(II) Complexes with Phenyl-N-[(pyridine-2-yl)methylene]methaneamide

摘要

The reaction of copper(II) chloride with phenyl-N-[(pyridine-2-yl)methylene]methaneamide (ppmma) leads to a new μ-chloro bridged dimeric [Cu(ppmma)Cl2]2 complex, whereas a reaction of copper(II) bromide with ppmma affords a monomeric Cu(ppmma)Br2 complex. Both complexes have been characterized by X-ray crystallography and electronic absorption spectroscopy. The crystal structural analysis of [Cu(ppmma)Cl2]2 shows that the two Cu(II) atoms are bridged by two chloride ligands, forming a dimeric copper(II) complex and the copper ion has a distorted square-pyramidal geometry (τ= 0.2). The dimer units are held through a strong intermolecular π-π interactions between the nearest benzyl rings. On the other hand, Cu(ppmma)Br2 displayed a distorted square planar geometry with two types of strong intermolecular π-π interaction. EPR spectrum of [Cu(ppmma)Cl2]2 in frozen glass at 77 K revealed an equilibrium between the mononuclear and binuclear species. The magnetic susceptibilities data of [Cu(ppmma)Cl2]2 and Cu(ppmma)Br2 follow the Curie-Weiss law. No significant intermolecular magnetic interactions were examined in both complexes, and magnetic exchange interactions are discussed on the basis of the structural features.