Synthesis and crystal structure of a cis-oxime-oximate bridged tetra coordinated open-book shaped new dicopper(II/II) complex [Cu2(μ-Hdmg)2(Hdmg)]ClO4: First report of unusual oxime OH bridging

Reaction of Cu(ClO4)2 · 6H2O with dimethylglyoxime (H2dmg) and triethylamine (pH ∼ 4–5) at room temperature affords oxime bridged dicopper(II/II) complex of formula [Cu2(μ-Hdmg)2(Hdmg)]ClO4 · H2O (1) (H2dmg = dimethylglyoxime). The complex has been characterized by single-crystal X-ray diffraction analysis. The structure consists of one dinuclear complex cation, [Cu2(μ-Hdmg)2(Hdmg)], and one View the MathML sourceClO4- anion. Two copper(II) ions at a distance of 3.558 Å are bridged by one oxime and one oximate groups in cis arrangement. The geometry around each copper atom is square planar with an overall open-book type arrangement of these planes. The average copper–oxygen distance is (1.953 Å) and the average copper-nitrogen distance is 2.003 Å. The Cu–O(oxime) distance (1.963 Å) is higher than the Cu–O(oximate) distance (1.942 Å) due to different protonation label. The room temperature value of χMT for the title complex (χM being the molar magnetic susceptibility for two copper atoms) is low (ca. 0.42 cm3 K mol−1) (μeff = 1.52 μB). The UV–Vis spectrum of the complex shows a characteristic broad band at 470 nm.