Bis- and tris-chelates of NiII, CuII, CoII and FeIII bound to N,N-dialkyl/alkyl aryl-N′-benzoylthiourea ligands

•X-ray crystal structures of four complexes proved the orientation of the ligands.•Only mononuclear bis- and tris-chelates complexes were obtained.•Tautomerization resulted keto-thiol form of the ligands for metal ion binding.

Bis- and tris-chelates (1–5) of Ni(II), Cu(II), Fe(III) and Co(II) with two O,S donor substituted benzoylthiourea based ligands 3,3-diethyl-1-benzoylthiourea (HL1) and 3-methyl-3-phenyl-1-benzoylthiourea (HL2) have been synthesized and structurally characterized by X-ray crystallography. The keto-thione form of the free ligands transform to the keto-thiol form during coordination through neutral O and anionic S atoms. Crystallographic characterizations with supportive spectroscopic signatures confirm the cis-conformation in bis-chelates and facial binding to the tris-chelates.

Graphical abstractBenzoylthiourea based O,S donor ligands showed preference for cis- and fac-isomers for bis- and tris-chelates of 3d metal ions with keto-imine-thiol tautomerization.Figure optionsDownload full-size imageDownload as PowerPoint slide