In an effort to utilize [Co(NH 3 ) 6 ] 3+ cation as a new host for mono-, di- and tri-substituted nitrophenolate anions, yellow solids of composition [Co(NH 3 ) 6 ](4-np) 3. 4H 2 O, [Co(NH 3 ) 6 ](2,4-dnp) 3 , and [Co(NH 3 ) 6 ](2,4,6-tnp) 3 were obtained in high yields by reacting sodium salts of 4-np, 2,4-dnp and 2,4,6-tnp (where np=nitrophenolate, dnp=dinitrophenolate and tnp=trinitrophenolate,) with [Co(NH 3 ) 6 ]Cl 3 respectively in 3:1 molar ratio in hot aqueous medium. These cobalt(III) complex salts have been characterized by elemental analyses and spectroscopic techniques (UV/Visible, IR and NMR). Single crystal X-ray structure determination of [Co(NH 3 ) 6 ](4-np) 3. 4H 2 O revealed the presence of discrete ions, [Co(NH 3 ) 6 ] 3+ and C 6 H 4 NO 3 − in addition to four lattice water molecules in the solid state. A strong network of hydrogen bond interactions (N–H⋯O (phenolate), N–H⋯O (nitro), O–H⋯O (water) stabilize the crystal lattice. The formation of these salts and measurement of solubility products suggests that [Co(NH 3 ) 6 ] 3+ present in [Co(NH 3 ) 6 ]Cl 3 may be used as anion receptor for the nitrophenolate ions.