Acetato and formato copper(II) paddle-wheel complexes with nitrogen ligands

Compounds Cu(AcO)2(pydz) (1), Cu(HCOO)2(pymd)1/2 (2), Cu(AcO)2(pymd)1/2 (3), and Cu(AcO)2(4,4'-bipy)1/2 (4) were obtained by reactions of Cu(AcO)2H2O and Cu(HCOO)2 4H2O with pyridazine, pyrimidine, or 4,4'-bipyridine. In all the studied structures, the paddle-wheel units [Cu2[mu-RCOO)4] are present. Coppers show a square pyramidal coordination determined by four oxygens in the equatorial positions and a nitrogen in the axial position. Compound 1 consists of centrosymmetric dimeric molecules. Compounds 2 and 3 instead consist of zig-zag chains of [Cu2[mu-RCOO)4] units linked by bridging pyrimidine molecules. The chains run in the (1 0 1) and (1 1 -2) directions in 2 and 3, respectively. By crystallization of a solution of 4 in chloroform, Cu(AcO)2(4,4'-bipy)1/2 1/2CHCl3 (5) was obtained. It consists of monodimensional chains of [Cu2(mu-CH3COO)4] units linked by bridging 4,4'-bipy molecules. The chains, of two different types, run parallel to the b-axis in the crystal. Two chlorines of each CHCl3 molecule are close to two oxygens of two parallel chains. The packing can be described as sheets parallel to the (1 0 -1) plane. Magnetic properties and electron paramagnetic resonance spectra have been studied.