Unusual C–H⋯Ni anagostic interactions in new homoleptic Ni(ii) dithio complexes

Abstract

Six new homoleptic complexes of the general form [Ni(L₂)] [L = L1 (9-fluorenylmethyl)xanthate (1); L2 (cyclobutylmethyl)xanthate (2); L3 (1-benzyl-4-hydroxypiperidine)xanthate (3); L4 (N-benzyl-N-methylpyridyl)dithiocarbamate (4); L5 (N-methylfuryl-N-methylpyridyl)dithiocarbamate (5); L6 (N-benzyl-N-methylfuryl)dithiocarbamate (6)] have been prepared and characterized by microanalysis, spectroscopy (IR, ¹H and ¹³C NMR, UV-Vis) and their structures have been elucidated by X-ray crystallography. In all complexes the metals are four coordinate with square planar coordination geometries although in the crystal structures of 2 and 4 significant C–H⋯Ni anagostic intermolecular interactions in axial positions are found which involve the metal atom in chain motifs. As far as we are aware 2 and 4 are unique examples of homoleptic metal dithio complexes exhibiting such type of anagostic interactions. In the remaining complexes (1, 3, 5 and 6) supramolecular frameworks are stabilised by S⋯S, C–H⋯S, C–H⋯π and π⋯π non-covalent interactions. All six complexes are weakly conducting (σ_rt = 10⁻¹¹–10⁻⁸ S cm⁻¹; E_a = 0.37–1.40 eV) and show semiconductor behaviour in the 303–393 K temperature range.