The blue complex cis-[Ni(dipren) 2 (NO 3 )](NO 3 ) 1 and the greenish blue cis-[Ni(dipren) 2 (H 2 O) 2 ](NO 3 ) 2 2H 2 O 2 (dpren/dpren = dipropyl/diisopropylethane-1,2-diamine) have been synthesized. Complex 2 upon heating loses four water molecules in a single step and undergoes melting accompanied with colour change, greenish blue to deep green, 2a. Configuration of the complexes 1, 2 and 2a have been proposed to be cis-octahedral on the basis of magnetic, IR and electronic spectroscopic studies and confirmed in case of complex 1 by X-ray single crystal structure analysis. The role of steric factor of the alkyl groups on the selectivity of coordinating mode of nitrate ion is studied.