Crystal and molecular structure of bis[pyridine-2-(N-cyanocarboxamidato)]aquocopper(II), Cu(C5H4NCONCN)2(OH2)

Bis[pyridine-2-(N-cyanocarboxamidato)]aquocopper(II), Cu(C₅H₄NCONCN)₂(OH₂), has been prepared and its i.r. spectrum and crystal structure have been determined. The crystals are triclinic (P¯1):a = 11·45(1),b = 10·35(1),c = 7·48(1) Å, = 110·9(1), = 102·2(2), = 108·9(1)°,Z = 2. The X-ray analysis, carried out using three-dimensional Patterson, Fourier and least-squares methods (finalR = 5·7%), showed copper(II) to be pentacoordinated, with two organic ligands chelating through their pyridine [Cu-N = 1·997(4), 1·989(4) Å] and amide nitrogen atoms [Cu-N = 1·980(7), 2·006(6) Å], and with one water molecule at a distance [Cu-OH₂ = 2·335(4) Å] sensibly longer than the usual Cu-O(2·0 Å) coordinate bonds. The coordination polyhedron can be described either as a distorted tetrahedron formed by the nitrogen atoms with an extra position occupied by water or as a trigonal bipyramid having water and two nitrogen atoms in the equatorial plane. The packing determining interactions are the hydrogen bonds formed by water, and a long Cu...N (3·420 Å) contact between the metal and a nitrogen atom from an adjacent molecule.The authors are indebted to Prof. Immirzi who kindly supplied his computer programmes.