Synthesis, crystal structures and magnetic properties of new oxalato- and phenolato-bridged binuclear copper(II) complexes with Schiff-base ligands

Two binuclear complexes of copper(II), [(Hfsaaep)Cu(mu-C-2-O-4)Cu(Hfsaaep)] (1) and [Cu-2(Hfsadmpn)(2)(H2O)(2)](ClO4)(2) (2), have been synthesized by using Schiff-base ligands derived from 3-formyl-salicylic acid: 3-[N-2-(pyridylethyl)formimidoyl]salicylic acid (H(2)fsaaep) and 3-N-[N',N'-dimethylaminopropyl)formimidoyl]salicylic acid (H(2)fsadmpn). The crystal structures of compounds 1 and 2 have been solved. That of compound 1 consists of neutral binuclear entities with copper atoms bridged by one oxalato group, which connect axial-equatorial positions of the two coordination polyhedra. The copper atoms are related by an inversion center and exhibit a distorted square-pyramidal stereochemistry. The Cu...Cu distance within the binuclear unit is 5.482(l) Angstrom. The structure of 2 consists of cationic centrosymmetric binuclear entities and perchlorate anions. The tertiary amino groups from the ligands are protonated. The copper(II) ions are bridged by phenolic oxygen atoms, assuming a square-pyramidal geometry bridge the copper(II) ions. The apical. positions are occupied by the aqua ligands (Cu-O = 2.335(4) A). The distance between the copper atoms is 3.008(2) Angstrom. Cryomagnetic investigations of the two compounds reveal antiferromagnetic interactions between the copper ions in both compounds (1: J= -9 cm(-1); 2: J= -646 cm(-1)). (C) 2002 Elsevier Science B.V. All rights reserved.