Synthetic, structural and magnetic studies of asymmetric trinuclear copper(II) compounds [CuX2(Hae)2][Cu2(ae)2X2](X = Cl or Br; Hae = 2-aminoethanol)

Abstract

The structure of a novel complex [Cu^IIBr₂(Hae)₂][Cu^II₂(ae)₂Br₂]1(Hae = 2-aminoethanol) containing a neutral mononuclear copper unit bridged by a µ₄-bromide ion and hydrogen bonds to a dinuclear copper(II) unit has been determined: orthorhombic, space group Pbca, a= 15.726(2), b= 20.984(3), c= 12.637(1)Å, R= 0.049 (R′= 0.047), 1477 observed [l > 3.00σ(l)] reflections. The bridging bromide ion is unique; it links two copper(II) ions in the dinuclear unit and a mononuclear and two dinuclear units, thereby forming a chain-type structure. Hydrogen bonding additionally extensively stabilizes the formation of the chains along the c axis and links the chains together along the b axis. A very short O ⋯ O contact [2.61(2)Å] is present between a co-ordinated alcohol and an alcoholate of a different trinuclear unit. The resulting layers are connected only by van der Waals contacts. The synthesis, spectroscopic and magnetic properties of the complex are compared with those of the isomorphous chloride. The magnetic behaviour can be understood on the basis of the structure, and corresponds to that of a weakly antiferromagnetically coupled dinuclear unit and a mononuclear paramagnetic unit. The small value of the antiferromagnetic coupling can be explained by the roof-shaped CuO₂Cu unit, which prevents the magnetic orbitals from undergoing significant overlap.