In the present report, the reactivity of the binuclear complex [Ni2(µ-SeC5H4N)2(dppe)2]2+ towards dichloromethane and methanol has been studied. The complex [Ni2(µ-SeC5H4N)2(dppe)2]2+ in the presence of chlorinated solvent resulted in selenido bridged trinuclear complex of composition [Ni3(µ-Se)2(dppe)2]2+ (1) whereas in the presence of methanol hydrolyzed product having cubane core [Ni4{(C5H4N)2Se}4(μ3[sbnd]OH)4(C6H5COO)(HCOO)]2+ (2) was isolated. Both the complexes were characterized by elemental analysis, IR, 1H, and 31P{1H} NMR spectroscopy. An attempt has also been made to investigate their thermal studies. The molecular structure of both the complex [Ni3(µ-Se)2(dppe)2]2+ (1) and [Ni4{(C5H4N)2Se}4(μ3[sbnd]OH)4(C6H5COO)(HCOO)]2+ (2) were established by single-crystal X-ray diffraction analysis. Broken-symmetry density functional theory (BS-DFT) calculations were carried out on complex 2 to investigate the electronic structure and nature of magnetic exchange interaction. BS-DFT reveals the existence of three different J values i.e. -8.9 cm−1, +18.7 cm−1 and +1.8 cm−1 between different Ni(II) pairs. A strong ferromagnetic interaction was observed between formate/phenylacetate bridged Ni(II) centers. An antiferromagnetic interaction between the ferromagnetically coupled formate and phenylacetate bridged Ni(II) dimers result in isolation of S = 0 spin ground state for complex 2. Molecular orbital, spin-density analyses were performed on the X-ray and optimized geometries to probe the electronic structure of complex 2. © 2021