Synthesis, structures and magnetic properties of pentanuclear and trinuclear heterometallic complexes with bended and linear cyano-bridges (tren = tris(2-aminoethyl)amine)

Abstract

The reaction of [Cu(tren)(OH 2)](ClO 4) 2 with KCN gave a mononuclear complex [Cu(tren)(CN)](ClO 4) ( 1) (tren = tris(2-aminoethyl)amine). Using 1 as a building block, one pentanuclear compound, [{Cu(tren)(NC)} 4Ni](ClO 4) 6 ( 2) and two trinuclear complexes, [{Cu(tren)NC} 2Co(tren)](ClO 4) 5 · 2H 2O ( 3), [{Cu(tren)CN} 2NiL](ClO 4) 4 ( 4) (L = 3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane) were prepared and characterized by single crystal X-ray analysis. In 1, Cu(II) atom adopts a distorted trigonal bipyramidal (TBP) geometry. In 2, the Ni(II) atom occupies the center of the pentanuclear compound with a square-planar coordination geometry. In 3, the six-coordinated Co(III) atom presents a distorted octahedral geometry with four nitrogen atoms from tren and two carbon atoms of bridged cyano groups in cis-positions. In 4, the nickel atom is located in an inversion center and coordinated with two [(tren)CuCN] + moieties through cyano-bridging ligands. Magnetic susceptibility measurements of 2– 4 show that the magnetic interactions between the heterometallic ions are antiferromagnetical coupling through the cyano bridges with g = 2.25, J = −0.142 cm −1 and J′ = −0.167 cm −1 for 2, g = 2.06, J = −0.094 cm −1 for 3, and g = 2.20, J = −33.133 cm −1 for 4. The correlations between the structures and the J values are discussed.