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

Abstract

The complexes [Ni(L-1)(PPh3)] (1) and 1Ni(L-2)(PPh3)]-HCI (2) were synthesized by the reaction of [Ni(PPh3)Cl-2] and dibasic 2-hydroxyacetophenone-S-R-4-R-1-thiosemicarbazones (R/R-1: H/CH3, (LH2)-H-1; CH3/H, (LH2)-H-2). The ligands and the complexes were characterized using elemental analysis, IR and H-1 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 L-1 and the P acorn of a triphenylphosphine ligand. In complex 2, L-2 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 N-4 nitrogen (in complex 2). (C) 2011 Elsevier Ltd. All rights reserved.