New tetranuclear copper(II) complexes obtained by using compartmental and exo-dentate ligands

Abstract

The synthesis and crystal structures of two new tetranuclear complexes are described: [{L(μ-OH)Cu 2}(μ-fum){Cu 2(μ-OH)L}](ClO 4) 2 ( 1) and [{L(μ-OH)Cu 2}(μ-IN) 2{Cu 2(μ-OH)L}](ClO 4) 2·2C 2H 5OH·0.5H 2O ( 2). The two complexes have been obtained through self-assembly processes involving a binuclear copper(II) complex, [L(μ-OH)Cu 2](ClO 4) 2 (L stands for a compartmental end-off ligand, 2,6-bis[ N-2-pyridylethyl)formimidoyl]-phenolato), and exo-dentate ligands (the fumarate anion, fum 2−, and the isonicotinato anion, IN −). The crystal structure of 1 consists of centrosymmetric tetranuclear cationic species, which result by connecting two binuclear units with one dicarboxylato linker. Each carboxylato group forms a third bridge between the copper(II) ions within the binuclear moiety ( syn– syn bridging mode). The closest Cu⋯Cu distances in tetramer are 2.930(1) and 9.313(3) Å. Compound 2 contains cationic [Cu 4] rectangles, with the short edges constructed from the preexisting μ-OH and μ-phenoxo groups [3.062(1) Å], and the long ones constructed from the isonicotinato linkers [9.352(1) Å]. In both compounds the copper(II) ions are pentacoordinated with a square-pyramidal stereochemistry.