Solvent mediated synthesis of homoleptic tri and tetranuclear nickel complex derived from [Ni2(µ-SeC5H4N)2(dppe)2]²⁺ and theoretical studies

• Isolation of trinuclear [Ni 3 (µ-Se) 2 (dppe) 2 ] 2+ as well as novel tetranuclear complex [Ni 4 {(C 5 H 4 N) 2 Se} 4 (μ 3 OH) 4 (C 6 H 5 COO)(HCOO)] 2+ from the same precursor. • Dichloromethane as a solvent caused the cleavage of Se-C bond, whereas protic solvent assists in obtaining an intact cubane-like core-shell. • DFT calculations along with spin-density and molecular orbital analysis provide insight into the nature of magnetic interaction present in the cubane core-shell. In the present report, the reactivity of the binuclear complex [Ni 2 (µ-SeC 5 H 4 N) 2 (dppe) 2 ] 2+ towards dichloromethane and methanol has been studied. The complex [Ni 2 (µ-SeC 5 H 4 N) 2 (dppe) 2 ] 2+ in the presence of chlorinated solvent resulted in selenido bridged trinuclear complex of composition [Ni 3 (µ-Se) 2 (dppe) 2 ] 2+ ( 1 ) whereas in the presence of methanol hydrolyzed product having cubane core [Ni 4 {(C 5 H 4 N) 2 Se} 4 (μ 3 OH) 4 (C 6 H 5 COO)(HCOO)] 2+ ( 2 ) was isolated. Both the complexes were characterized by elemental analysis, IR, 1 H, and 31 P{ 1 H} NMR spectroscopy. An attempt has also been made to investigate their thermal studies. The molecular structure of both the complex [Ni 3 (µ-Se) 2 (dppe) 2 ] 2+ ( 1 ) and [Ni 4 {(C 5 H 4 N) 2 Se} 4 (μ 3 OH) 4 (C 6 H 5 COO)(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 .