Synthesis, structure and characterisation of [Ni(bipy)3][NaAl(ox)3]: (bipy = 2,2′-bipyridine, ox = oxalate)

Abstract

The compound [Ni(bipy)₃][NaAl(ox)₃], where ox^2– is the oxalate dianion and bipy is 2,2′-bipyridine, was obtained by mixing of K₂[Ni(ox)₂(H₂O)₂]·4H₂O and [H₂bipy]Cl₂ in silica hydrogel at room temperature. The complex, which incorporates Na and Al from the silica gel, was characterised by Fourier-transform IR spectroscopy, energy-dispersive X-ray analysis, thermogravimetric techniques and single-crystal X-ray diffraction. It crystallises in the cubic system, space group P2₁3, with a= 15.518(2)Å, U= 3736.9(8)ų and Z= 4. The crystal structure consists of a chiral, three-dimensional polymeric network of Al³⁺ and Na⁺ bridged by bis(bidentate oxalate) ligands, [NaAl(ox)₃]_n^2n–, with the [Ni(bipy)₃]²⁺ cations inserted in the anionic network cavities. The cations and anionic network are held together by means of electrostatic forces and weak C–H ⋯ O hydrogen bonds.