Copper(II) complexes of optically active binucleating ligands, N,N′-bis[2-pyridylmethyl and 2-(2-pyridyl)ethyl]-(S)-malamide and related amides

Abstract

N,N′-Bis(2-pyridylmethyl)-3-hydroxyglutaramide [abbreviated as H 3(pmg)], optically active N,N′-bis{2-pyridylmethyl and 2-(2-pyridyl)ethyl}-(S)-malamide [H 3(lpm) and H 3(lpe), respectively], and the optically inactive analogues [H 3(ppm) and H 3(pem)] gave dimeric copper(II) complexes [Cu 2XL]·nH 2O (L = 1pm, 1pe, pmm, pem, and pmg; X = an anionic, exo-bridging ligand such as chloride, hydroxide, acetate (OAc), pyrazolate (pz), and nitrite ions). These complexes were characterized by magnetic susceptibilities, and electronic, circular dichroism, and infrared spectra. The amides act as a trivalent anionic ligand coordinating through the pyridine- and deprotonated amido-nitrogen atoms and through the deprotonated, pendant alkoxooxygen atom bridging two copper ions. Many of the complexes were magnetically subnormal at room temperature, the magnetic interaction between the two copper ions depending upon both L and the exo-bridges, X. The antiferromagnetic interaction increased in the order of X, Cl < OAc < OH < NO 2 < pz. Temperature dependence of the magnetic susceptibilities of some of the 1pm complexes ensured the order. A diamagnetic nickel(II) complex, Ni 2(pz)(lpm) · 2H 2O and a heterometallic CuNi(pz)(lpm) · 2H 2O were also obtained. The binuclear structure of Cu 2(pz)(ppm) · 3H 2O was confirmed by X-ray analysis.