Synthesis, crystal structure and Hirshfeld surface analysis of diaquabis( o -phenylenediamine-κ 2 N , N ′)nickel(II) naphthalene-1,5-disulfonate

The reaction of o -phenylenediamine (OPD), sodium naphthalene1,5-disulfonate (Na 2 NDS) and nickel sulfate in an ethanol–water mixture yielded the title compound, [Ni(OPD) 2 (H 2 O) 2 ]·NDS or [Ni(C 6 H 8 N 2 ) 2 (H 2 O) 2 ](C 10 H 6 O 6 S 2 ). This salt consists of a complex [Ni(OPD) 2 (H 2 O) 2 ] 2+ cation with two bidentate OPD ligands and trans aqua ligands, and a non-coordinating NDS 2– anion, which is the double-deprotonated form of H 2 NDS. The Ni II atom is situated at a center of inversion and exhibits a slightly tetragonally distorted {O 2 N 4 } octahedral coordination environment, with four shorter equatorial Ni—N bonds [2.0775 (17) and 2.0924 (18) Å] and a longer axial Ni—O bond [2.1381 (17) Å]. The OPD ligand is located about an inversion center and is nearly coplanar with the NiN 4 plane [dihedral angle 0.95 (9)°]. In the crystal, the cations and anions are connected by charge-assisted intermolecular N—H...O and O—H...O hydrogen-bonding interactions into the tri-periodic network structure. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H...H (44.1%), O...H/H...O (34.3%), C...H/H...C (14.8%) C...C (6.5%) (involving the cations) and O...H/H...O (50%), H...H (25%), C...H/H...C (15.3%), C...C (8.2%) (involving the anions) interactions.