Two pyrazolato-bridged, linear trinuclear Cu(II) complexes. Crystal structures and magnetic properties

The single-crystal X-ray structures of two new linear trinuclear copper(II) complexes of 3,5-pyrazoledicarboxylic acid (H3L) are reported, viz. [Cu3(L)2(Me2en)2(H2O)2]·(H2O)8 (1) and [Cu3(L)2(MeOH)6(H2O)4] (2), with Me2en is N,N-dimethylethylenediamine. Both complexes are trinuclear and have been obtained from a precursor ligand, through copper-induced amide hydrolysis. In 1, the central copper ion is in a distorted square-planar environment and the two outer copper ions are in a distorted square-pyramidal environment. All three copper ions in 2 are six-coordinated in an elongated octahedral environment. A weak, broad EPR signal centered around g=3.5, indicative for an S=3/2 state, is observed and confirms both complexes to be trinuclear. Magnetic susceptibility measurements of 1 and 2 from 4 to 300 K indicate a weak anti-ferromagnetic exchange coupling, with J values of −15 and −19 cm−1, respectively.