Centrosymmetric Nickel(II) Complexes Derived from Bis-(Dithiocarbamato)piperazine with 1,1′-Bis-(Diphenylphosphino)ferrocene and 1,2-Bis-(Diphenylphosphino)ethane as Ancillary Ligands: Syntheses, Crystal Structure and Computational Studies

Two Ni(II) complexes with the formula [{Ni(dppf)}₂{(L1)₂}](PF₆)₂ (Ni-I) and [{Ni(dppe)}₂{(L1)₂}](PF₆)₂ (Ni-II) were prepared by reacting [Ni(dppf)Cl₂] and [Ni(dppe)Cl₂] (dppf = 1,1′-Bis-(diphenylphosphino)ferrocene; dppe = 1,2-Bis-(diphenylphosphino)ethane) with secondary amine piperazine derived ligand disodium bis-(dithiocarbamate)piperazine ((piper(dtc)₂ = L1) and counter anion PF₆⁻. These complexes were characterized by elemental analyses, FT-IR, ¹H, ¹³C and ³¹P NMR, UV-Vis. spectroscopy and single crystal X-ray diffraction. The X-ray analyses reveal centrosymmetric structures where each Ni(II) centre adopts distorted square planar geometry defined by two sulfur centres of dithiocarbamate ligand and two phosphorus centres of dppf and dppe ligands in Ni-I and Ni-II, respectively. The supramolecular framework of both Ni-I and Ni-II are sustained by C-H⋯π and C-H⋯F interactions, and they also display interesting intramolecular C-H⋯Ni anagostic interactions. Further, the nature of these interactions are studied using Hirshfeld surface analyses, DFT and quantum theory of atoms in molecules (QTAIM) calculations. Additionally, non-covalent interaction (NCI) plot analyses were conducted to gain additional insight into these non-covalent interactions. This work is vital in a new approach towards the rational designing of the centrosymmetric molecules with interesting architectures.