Self assembly of homoleptic Ni(ii) dithiocarbamates and dithiocarbimates via Ni⋯H–C anagostic and C–H⋯π (chelate) interactions

Abstract

New homoleptic complexes of the form [Ni(L)₂] (L = L¹ (dibenzyl dithiocarbamate) 1, L² (N-benzyl-N,N-dimethyl ethylene dithiocarbamate) 2, and (R)₂[Ni(L³)₂)] (L³ = p-chlorobenzene sulfonyl dithiocarbimate; R = (C₂H₅)₄N⁺3, (C₃H₇)₄N⁺4, (C₆H₁₃)₄N⁺5) have been prepared and characterized by elemental analyses, IR, ¹H and ¹³C NMR and UV-visible absorption spectra. In addition, their structures have been elucidated by X-ray crystallography. The crystal structure of 1 reveals unusual C–H⋯Ni intermolecular anagostic interactions in axial positions resulting in 1D supramolecular chains, whereas complex salts 3 and 5 display unique C–H⋯Ni anagostic interactions due to the close proximity of one or two methylene protons in the cationic moieties to the Ni(II) center of the [Ni(L³)₂]²⁻ complex anion, providing pseudo-square pyramidal and octahedral coordination environments respectively about the metal centers. To the best of our knowledge, 3 and 5 are the first examples of inter-ionic anagostic interactions within dithio complexes. Theoretical calculations have been performed for 3 and 5. The energy of interaction for 3 and 5 was found to be more than the previously reported neutral complexes. The supramolecular networks in all the complexes are sustained by non-conventional C–H⋯O, C–H⋯N and C–H⋯π (chelate, NiS₂C) bonding interactions. All complexes are weakly conducting with σ_rt ∼10⁻⁶ S cm⁻¹.