Diaquabis(pyridine-2 2)Nickel(II) Disaccharinate Tetrahydrate

Abstract

In the crystal structure of the title compound, [Ni(C<inf>6</inf>H <inf>6</inf>N<inf>2</inf>O)<inf>2</inf>-(H<inf>2</inf>O)<inf>2</inf>](C <inf>7</inf>H<inf>4</inf>NO<inf>3</inf>S)<inf>2</inf>·4H<inf>2</inf>O or [Ni(pia)<inf>2</inf>(H<inf>2</inf>O)<inf>2</inf>](sac) <inf>2</inf>·4H<inf>2</inf>O (pia is picolinamide or pyridine-2- carboxamide, and sac is the saccharinate anion), the Ni2+ cation, located on a centre of symmetry, is coordinated by two symmetry-related aqua ligands together with a pair of symmetry-related bidentate pia molecules and exhibits a distorted octahedral environment. The unique unligated sac anion in the asymmetric unit resides on a general position and has a single negative charge. The coordinated water molecules link the sac ions to the metal complex via O - H⋯O hydrogen bonds. In addition, the sac ions are linked to the metal complex via intermolecular π-π interactions between the benzene ring of the sac ion and the pyridine ring of a pia ligand. Each uncoordinated water molecule is hydrogen bonded to sac moieties through O - H⋯O and O - H⋯N hydrogen bonds.