Thermal and spectroscopic investigations of 4-nitrobenzoate complexes of Ni(II)

Abstract

The complexes [Ni(H2O)4(4-nba)2].2H2O 1 (4-nba is 4-nitrobenzoate) and [Ni(H2O)6](4-nba)2.2H2O 2 were prepared by the reaction of nickel carbonate or hydroxide with 4-nitrobenzoic acid (4-nbaH) and the formation of these complexes is pH dependent. Complex 1 is isostructural with the corresponding Co complex. The complexes have been characterised by elemental analaysis, IR spectra and can be thermally decomposed to the corresponding oxide. Complex 1 can be reversibly hydrated as evidenced by IR spectra and X-ray powder pattern. In contrast the octahydrate complex of Ni(II) cannot be reversibly hydrated. Calcining 2 at 170 degrees results in the formation of the dihydrate and attempts to remove the last two water molecules results in the breakdown of the structure indicating that these water molecules are strongly held in 2.