Dinuclear and mononuclear copper(II) carboxylate complexes with cis-chelating diacids

The synthesis and crystal structures of two new copper complexes with chelating dicarboxylic acids are described. Reaction of copper(II) acetate with diacid H2L2 (HO2CC(Me)2OArOC(Me)2CO2H, Ar=1,3-substituted phenyl) gave a bischelate complex (L2)2Cu2 · 2MeOH with the normal paddlewheel structure and tilted, trans-oriented chelate rings with skewed conformations. The overall structure was reasonably well reproduced by density functional calculations on (L2)2Cu2. Treatment of the product from reaction of Cu2(OAc)4 and diacid H2L3 (Ar=1,3-substituted 2,4-dibromophenyl) with pyridine gave a six-coordinate mononuclear chelate (L3)Py2Cu · H2O in which one chelate carboxylate is monodentate, the other is unsymmetrically bidentate, and the pyridines are cis-coordinated.