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 σrt ∼10−6 S cm−1.