Crystal and molecular structures of two crystalline forms of isothiocyanato-[1,7-bis-(2-pyridyl)-2,6-diazaheptane]copper(II) thiocyanate

Abstract

The single-crystal, X-ray analyses of two of the crystalline forms (α and γ) of the title compound have shown the crystals to be : α, triclinic, space group P, a= 16·66(4), b= 7·88(2), c= 9·11(3)Å, α= 124·4(1), β= 83·0(1), γ= 91·6(1)°; γ, monoclinic, space group B2₁/c, a= 26·75(7), b= 7·62(2), c= 19·08(5)Å, β= 90·36(5)°. The structures, which have refined to R 0·103 (α, 2648 independent reflections) and 0·116 (γ, 2358 independent reflections), are conformational isomers each involving a complex cation containing five-co-ordinate copper(II) in a distorted trigonal bipyramidal geometry and a thiocyanate ion in the lattice. The isomerism arises from the different configurations at the aliphatic nitrogen atoms of the tetramine ligands in the two compounds. All copper–nitrogen(tetramine) distances are close to the mean value of 2·016 Å with a slight tendency for equatorial bonds to be longer than axial bonds. In the co-ordinated isothiocyanate groups the mean Cu–N–C angle is 155·7°; Cu–NCS is 2·141 Å.