Bidentate coordination behaviour of a potentially tridentate ligand. A mononuclear four-coordinate Ni(II) complex supported by two <i style="">o</i>-iminobenzosemiquinonato units

Abstract

Using a new<i style=""> N,O,S</i>–potentially tridentate ligand (H₂L), a mononuclear Ni^II complex of composition <b style=""></b> (<b style="">1</b>) has been synthesized. The structure of the complex has been elucidated<b style=""> </b>in the solution state using ¹H NMR spectroscopy and in the solid state by X-ray crystallography. X-ray studies reveal that the Ni^II is surrounded by two <i>o</i>-iminobenzosemiquinonate(1–) <i><img src='/image/spc_char/pi.gif' border=0></i>-radical ligands, providing a Ni^IIN₂O₂ square planar coordination environment. Notably, the thioether unit in each ligand remains non-coordinated. Cyclic voltammetric measurements of (<b style="">1</b>) show two one-electron reductive and two one-electron oxidative redox responses, which are ligand-centred in origin. Characterization of electrochemically-generated reduced and oxidized species has also been accomplished.