Synthesis, NMR spectral and single crystal X-ray structural studies on Ni(II) dithiocarbamates. Fabrication of nickel sulfide nanospheres by the solvothermal method

Three dithiocarbamatonickel(II) complexes, [Ni(bzbudtc)₂] (1), [Ni(bzbudtc)(PPh₃)(NCS)] (2) and [Ni(bzbudtc)(PPh₃)(CN)] (3) (where, bzbudtc = the N-benzyl-N-butyldithiocarbamato anion and PPh ₃ = triphenylphosphine), were prepared. All three complexes were analyzed by UV-Vis, IR and NMR (¹H, ¹³C and ³¹P) spectra. The ¹³C NMR spectra of complexes 1-3 show the most crucial thioureide signal at around 200 ppm. A significant deshielding observed for the ³¹P signals in 2 and 3 reveals the effective bonding of phosphorus to the metal center. Single crystal X-ray analysis of crystals of 1-3 show that all the described complexes exhibit a distorted square planar coordination geometry in the solid state as a result of the small bite angle of the dithiocarbamato ligand. The observed magnitude of deviation out of the mean plane of nickel is in the following order: 1 < 3 < 2. A decrease in the thioureide bond distances in 2 and 3, in contrast to 1, could be accounted for by the difference in the steric effect induced by the triphenylphosphine (PPh₃) group. In the case of compound 1, solvothermal experiments were performed in order to produce nickel sulfide nanoparticles. The morphological and structural properties of the resultant particles indicate that the average size of the crystals is about 22 nm and the main component of the product is in the form of cubic face-centered NiS₂ (vaesite) with a minor fraction of hexagonal NiS.