Synthesis, structure, spectroscopy, and magnetism of two new dinuclear carbonato-bridged Cu(II) complexes

Abstract

Two new dinuclear μ-CO32-Cu(II) complexes with different coordination modes for the carbonato bridge have been obtained by fixation of atmospheric CO2and also directly prepared from the carbonate salt. The compounds comprise: [Cu2(μ-CO3)(dpyam)4](ClO4)2(H2O)4(1), and [Cu2(μ-CO3)2(dpyam)2](H2O) (2), (in which dpyam = di-2-pyridylamine). For 1, the carbonate ligand acts as a bridge between two Cu(II) centres showing an anti-anti (μ-η1-η1-CO32-) coordination mode with a distorted square-based pyramidal geometry for each Cu(II) environment. Complex 2 involves the di-μ-CO32-bridge with a novel tridentate μ-η1-η2-CO32-coordination mode. The geometry around each copper atom is distorted square-based pyramidal. Susceptibility measurements for both complexes show a weak to moderately strong antiferromagnetic coupling with J values of -90.4 and -9.9 cm-1for 1 and 2, respectively. The tridentate co-ordination mode of the carbonate bridge in 2 has not previously been reported for dinuclear Cu(II) complexes. Also its magnetic behaviour and superexchange pathway are discussed. © 2001 Elsevier Science B.V. All rights reserved.