Synthesis, structure and magnetic properties of trinuclear complexes of copper(II) with different amines as terminal ligands

Abstract Three new trinuclear copper(II) complexes were synthesized: {[(ettmd)Cu] 2 [μ-Cu(pba)]}(ClO 4 ) 2 ( 1 ), {[(pmd)Cu] 2 [μ-Cu(Me 2 pba)]}(ClO 4 ) 2 ·3H 2 O ( 2 ) and {[(bapa)Cu] 2 [μ-Cu(Me 2 pba)]} ( 3 ) where Cu(pba) = 1,3-propanediyl-bis)oxamato)cuprate(II), Cu(Me 2 pba) = 2,2-dimethyl-1,3propanediyl-bis(oxamato)cuprate(II), ettmd = 4-ethyl-1,1,7,7-tetramethyldiethylenetriamine; pmd = N,N,N′,N″, N″-pentamethyldiethylenetridetermined by X-ray analysis. The crystals of 1 are monoclinic, space group P 2 1 / c , with a = 18.463(4), b = 14.402(3), c = 16.537(4) A, β = 109.00(3)°, Z = 4 and R = 0.072 for 2447 reflections observed. The crystals of 2 are triclic, space group P 1 − , with a = 19.610(4), b = 16.626(4), c = 16.007(3) A, α = 115.75(3)°, β = 89.97(3)°, γ = 100.86(4)°, Z = 4 and R = 0.068 for 7342 reflections observed. The crystals of 3 are orthorhombic, space group Pcba , a = 40.492(4), b = 16.363(3), c = 10.944(3) A, Z = 8 and R = 0.034 for 1634 reflections observed. The central copper(II) ions of compounds 1 and 2 are square-pyramidal, the apical positions being occupied by a perchlorate anion. In 3 the central copper ion is square-planar. The terminal copper ions of compounds 1 , 2 and 3 are all pentacoordinated with geometries that are intermediate between square-pyramidal and trigonal-bipyramidal. If the coordination is described in terms of square-pyramidal geometry, the basal plane of each terminal copper atom is approximately perpendicular to the basal plane of the central copper ion. The distortion towards trigonal-bipyramidal geometry is largest for compound 1 and smallest for 3 . Magnetic susceptibility measurements were carried out for this series of complexes. The magnetic data were interpreted using the Heisenberg Hamiltonian and led to J values of −137.1, −128.1 and −92.1 cm −1 for 1 , 2 and 3 , respectively. The intensity of the magnetic coupling is discussed in terms of the relative orientation of magnetic orbitals.