Nickel(II) complexes from phosphor-dichalcogenide (P/Se2 and P/S2) type ligands: Synthesis, structure and theoretical calculations

Abstract

Two new nickel phosphor-1,1-dichalcogenide complexes were synthesized from the reaction between Ni(II) salt and diselenophosphonate and dithiophosphonate ligands, forming complexes [Ni{Se2PPh(OEt)}2] 1 and [Ni{S2P(4-C6H4OMe) (OCH(CH2CH3)2}2] 2, respectively. Complexes 1 and 2 were fully characterized by single-crystal X-ray diffraction, 1H and 31P NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis. Both complexes crystallized in the triclinic P-1 space group and adopted a square planar geometry around the central Ni atom which was also positioned on a crystallographic inversion centre. The bond lengths of Ni–Se in 1 was on average 2.34 Å whilst for Ni–S in 2 unsurprisingly shorter in the range 2.21–2.23 Å. Complexes 1 and 2 has the same metal centre, and similar geometries, coordination modes and ligand types, differing only in chalcogenide donor atom binding to the metal, making 1 and 2 good candidates for theoretical studies and comparisons with experimental results. Density functional theory (DFT) was utilized to explain the structural and electronic properties of complexes. The DFT calculations employed B3LYP functional with 6-31 + G (d,p) basis set for ligand atoms and LANL2DZ for the central metal ions to obtain an optimized geometrical structure, and to perform an electronic and natural bond orbital (NBO) analysis.