The Crystal Structure of Bis(pyridine-2-carboxamido)nickel(II) Dihydrate

Abstract

The orange-red, diamagnetic crystals of [Ni(pia)₂]·2H₂O (piaH: pyridine-2-carboxamide) have been subjected to X-ray crystallographic analysis. They are orthorhombic, space group Pm2₁b-C_2v², with two formula units in a cell of dimensions: a=7.61, b=20.19 and c=4.46 Å. The crystals consist of planar molecules in which Ni(II) exhibits a square planar coordination and the two ligands are coordinated to the central nickel atom with four nitrogen atoms in trans-configuration. The molecules are tilted about 40° with respect to the plane (001), and are piled up above one another along the c-axis to form columns. These columns are linked with each other by intermolecular hydrogen bonds of N–H···O type, thus forming layers parallel to the plane (010). The layers are piled up along the b-axis by way of two water molecules which are hydrogen-bonded to the oxygen atoms of the amide groups. There exist stacking faults along this direction.