Crystal structures and magnetic properties of binuclear copper(II) complexes with alkoxo and benzoato or silanecarboxylato bridges

The crystal structures of the binuclear copper(II) complexes [Cu₂(L-ac)(PhCOO)] (1), [Cu₂(L-ac)(2-Me-PhCOO)· 1/2MeOH (2), [Cu₂(L-ac)(2,6-Me₂-PhCOO)] (3), [Cu₂(L-ac)(2,6-Cl₂-PhCOO)] · 0.7DMF (4), and [Cu₂(L-ac)(Ph₂MeSiCOO)] (5) were determined by X-ray diffraction. The ligand H₃(L-ac) is a 1:2 Schiff base derived from 1,3-diaminopropan-2-ol and acetylacetone. These complexes are antiferromagnetic and their -2J values are (1) 183, (2) 188, (3) 133, (4) 207, and (5) 95 cm^-1, respectively. A rough positive correlation between the Cu ⋯ Cu distance and the -2Jvalue was observed except for 5. The smaller -2Jvalue of the triorganosilanecar-boxylato complex, 5, than the benzoato complexes, 1-4, indicates a stronger orbital countercomplementary effect in 5. The geometrical parameters in the benzoato bridge have a minor effect on the magnitude of the antiferromagnetic interaction.