Second-sphere coordination complex via hydrogen bonding: Synthesis, characterization, X-ray crystal structure determination and packing of hexaamminecobalt(III) chloride di(para-nitrobenzoate)

A reddish orange coloured crystalline solid of hexaamminecobalt(III) chloride di(para-nitrobenzoate) was obtained when hexaamminecobalt(III) chloride was reacted with the sodium salt of para-nitrobenzoic acid (1:3 molar ratio) in hot aqueous medium. This cobalt(III) complex salt has been characterized by elemental analyses and spectroscopic techniques (e.g. UV/visible, IR and NMR). Single-crystal X-ray structure determination of the title complex salt revealed that it contains the cationic cobaltammine ([Co(NH3)6]3+) and mixed anions (Cl−, NO2C6H4COO−), which are held together by electrostatic forces attractions through second-sphere coordination, i.e. N–H⋯O (carboxylate and nitro) and N–H⋯Cl hydrogen bonds, resulting in a three-dimensional network.