Nickel(II)–triphenylphosphine complexes of ONS and ONN chelating 2-hydroxyacetophenone thiosemicarbazones

The complexes [Ni(L1)(PPh3)] (1) and [Ni(L2)(PPh3)]·HCl (2) were synthesized by the reaction of [Ni(PPh3)Cl2] and dibasic 2-hydroxyacetophenone-S-R-4-R1-thiosemicarbazones (R/R1: H/CH3, L1H2; CH3/H, L2H2). The ligands and the complexes were characterized using elemental analysis, IR and 1H NMR spectra. In both complexes, the thiosemicarbazone ligands coordinate to nickel(II) by giving two protons. Complex 1 is formed through the phenolate oxygen, azomethine nitrogen and sulfur atoms of L1 and the P atom of a triphenylphosphine ligand. In complex 2, L2 is functional through an ONN donor set, containing a thioamide nitrogen instead of a sulfur atom. X-ray analysis indicated distorted square planar structures for the complexes, and the nickel atoms lie slightly above the planes structured by the donor atoms. In the crystal forms of 1 and 2, some phenyl ring protons of the phosphine ligand give intramolecular hydrogen bonds with the donor atoms of the thiosemicarbazone moiety, namely the phenolate oxygen (in complexes 1 and 2) and N4 nitrogen (in complex 2).

Graphical abstractThe complexes [Ni(L1)(PPh3)] (1) and [Ni(L2)(PPh3)]·HCl (2), of 2-hydroxy-acetophenone thiosemicarbazones S-R 4-R1-thiosemicarbazones (R/R1: H/CH3, L1; CH3/H, L2) were synthesized and characterized. Complex 1 formed through ONS donor set of the thiosemicarbazone and P atom of triphenylphosphine ligand in monoclinic space group P21/c. Complex 2 consist of the ONN set and P atoms of the ligands, and this complex crystallizes in the triclinic space group P1¯. The donor atoms have taken place in the edges of a slightly deformed square planar, and nickel atom is slightly above the plane. Phospine protons give intramolecular hydrogen bonds with phenolate oxygen and thioamide nitrogen of these thiosemicarbazones.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Nickel complexes of ONS and ONN chelating thiosemicarbazones.