The Coordination of the Perchlorate Ion. I. The Crystal and Molecular Structure of Bis(perchlorato)bis(pyrazine-2,3-dicarboxamide)copper(II)

Abstract Bis(perchlorato)bis(pyrazine-2,3-dicarboxamide)copper(II) has been prepared, and its crystal and molecular structure has been determined by the X-ray diffraction and the infrared spectroscopic methods. The crystals are triclinic with a space group P\bar1; a=10.959(4), b=6.970(3), c=7.666(3) Å, α=116.63(3), β=78.14(5), and γ=97.27(5)°, and Z=1. The refinement of the crystal structure has been carried out by a block-diagonal least-squares method to give R=0.054 for 1727 non-zero reflections. The complex is centrosymmetric, with the two bidentate ligand molecules chelating to the copper atom in trans positions through the amide oxygen and pyrazine nitrogen atoms to form a square-plane. The two perchlorate ions coordinate weakly to the copper atom through the oxygen atoms from the top and bottom of this plane; thus, an elongated octahedron is formed. The complex molecules are connected to one another by N–O type hydrogen bonds to form a three-dimensional network. The infrared spectrum has been compared with that of the chloride complex. The KBr region clearly show the symmetry depression of the perchlorate ion from Td to C3v on coordination.