Structure–magnetism correlation in dimeric copper(II) carboxylates: crystal and molecular structure of tetra-µ-(propanoato-O,O′)-bis[aquacopper(II)]

Abstract

The dimeric copper(II) carboxylates [{Cu(O₂CR)₂(H₂O)}₂] and [{Cu(O₂CR)₂}₂](R = Et or Prⁿ) have been prepared and characterized by means of spectroscopic, magnetic, and thermogravimetric analyses. For [{Cu(O₂CEt)₂(H₂O)}₂] the crystal and molecular structure has also been determined. The crystals are monoclinic, space group P2₁/c, with a= 15.102(7), b= 17.186(5), c= 15.190(4)Å, β= 94.24(3)°, and Z= 4. Full-matrix least-squares refinement, using 1 784 independent reflections converged to a conventional R factor of 0.0561. The unit cell contains four crystallographically independent copper(II) atoms which give rise to three binuclear molecules with copper(I) acetate monohydrate type geometry. Two of these dimers are centrosymmetric with the symmetry centre at the middle of the Cu–Cu bond. Comparison of the present structural data and |2J| values with those of other structurally known dimeric copper(II) alkanoates does not allow an unambiguous determination of a specific ligand parameter to be the major factor in determining the magnitude of |2J|, and suggests that it may be the result of several modes of interaction.