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

The reaction of copper(II) chloride with phenyl-N-[(pyridine-2-yl)methylene]methaneamide (ppmma) leads to a new mu-chloro bridged dimeric [Cu(ppmma)Cl(2)](2) complex, whereas a reaction of copper(II) bromide with ppmma affords a monomeric Cu(ppmma)Br(2) Complex, Both complexes have been characterized by X-ray crystallography and electronic absorption spectroscopy. The crystal structural analysis of [Cu(ppmma)Cl(2)](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 (tau= 0.2). The dimer units are held through a strong intermolecular)pi-pi 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 pi-pi interaction. EPR spectrum of [Cu(ppmma)Cl(2)](2) in frozen glass at 77 K revealed an equilibrium between the mononuclear and binuclear species. The magnetic susceptibilities data of [Cu(ppmma)Cl(2)](2) and Cu(ppmma)Br(2) 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.