Syntheses, crystal structures and magnetic properties of mono- and polynuclear [bis(2-arylcarbonyl)amidate]copper(II) complexes

Five copper(II) complexes of formulas [Cu(bpcam)(CN)(H2O)] (1), [Cu(bpcam)(N-3)(H2O)](2) (2), [Cu(bpcam)(NCS)(H2O)] (3), [Cu(bpcam)(dca)(H2O)](2) (4) and [Cu(bpca)(tcm)](n) (5) [bpcam=bis(2-pyrimidylcarbonyl)amidate, bpca=bis(2-pyridylearbonyl)amidate, dca = dicyanamide and tcm = tricyanomethanide] have been prepared and their structures determined by single crystal X-ray diffraction. Compounds 1 and 3 are mononuclear species where each copper atom is five coordinated with a tridentate bpcam, and a terminally bound cyanide (1)/thiocyanate (3) ligands creating a basal plane with a water molecule in the axial position of a distorted square pyramid. Compound 2 is made of neutral di-mu-1,1-azidobis[(aqua)(bpcam)copper(II)] dinuclear and aqua(azido)(bpcam)copper(II) mononuclear units. The copper-copper separation in the dinuclear entity is 3.730(5) angstrom. The structure of 4 consists of neutral di-mu-1,3-dcabis[(aqua)(bpcam)copper(II)] units, the intramolecular copper-copper distance being 5.701(3) angstrom. Compound 5 is a uniform copper(II) chain where the [Cu(bpca)](+) units are connected through single [mu-1,5-tcm bridges which link one equatorial position of a copper atom with the apical position of the adjacent copper. The intrachain copper-copper separation in 5 is 7.688(3) angstrom. Magnetic susceptibility measurements of 2, 4 and 5 in the temperature range 1.9-295 K show the occurrence of weak antiferromagnetic interactions between the copper(II) ions, J 1.7 (2), -0.53 (4) and -0.64 cm(-1) (5) [the Hamiltonians used being defined as H = -JS(1) center dot S-2 (2 and 4) and H = -J Sigma S-i(i) center dot Si+1 (5)]. (c) 2007 Elsevier Ltd. All rights reserved.