title: Neutral Ni(II), Pd(II) and Pt(II) ONS-pincer complexes of 5-acetylbarbituric-4N-dimethylthiosemicarbazone: synthesis, characterization and properties.
abstract: Octahedral 1:1 Ni(II) and square-planar 1:1 Pd(II) and Pt(II) complexes of formulae [Ni(HAcb4DM)(AcO)(H2O)2]·H2O (1), [Pd(HAcb4DM)Cl]·5H2O (2) and [Pt(HAcb4DM)Cl]·3H2O (3), where H2Acb4DM = 5-acetylbarbituric-4N-dimethylthiosemicarbazone (H2 denoting its two dissociable protons, one enolic and one thiolic), have been synthesized and characterized by elemental analysis and by 1H and 13C NMR, UV-vis, and IR spectroscopy. Crystallisation of compounds 1–3 from DMSO afforded complexes of formulae [Ni(HAcb4DM)2]·2H2O (1a), [Pd(Acb4DM)(DMSO)]·DMSO (2a) and [Pt(Acb4DM)(DMSO)]·DMSO (3a), the molecular and crystal structures of which were determined by X-ray diffractometry. The thiosemicarbazone in 1a coordinates to the metal ions in an ONS-tridentate manner in the O-enolate/S-thione form, but in complexes 2a and 3a the thiosemicarbazone binds Pd(II) or Pt(II) as an ONS-pincer ligand in the O-enolate/S-thiolate form. The 195Pt NMR spectrum of 3 shows a signal at −2950 ppm along with two new signals at −3348 and −2731 ppm, indicating the presence of solvolysis products. The catalytic activity of complex 2a has been explored in aryl–aryl Suzuki cross-coupling reactions. H2Acb4DM and complexes 2 and 3 were screened for in vitro cytotoxicity against a human tumour cell line (HeLa-229), with the clinically employed drug cisplatin as a reference.
authors.affiliation: Universidad de Santiago de Compostela, Departamento de Química Inorgánica, Facultad de Farmacia, Santiago de Compostela, 15782, Spain.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Castiñeiras
authors.forename: Nuria
authors.initials: N
authors.lastname: Fernández-Hermida
authors.forename: Isabel
authors.initials: I
authors.lastname: García-Santos
authors.forename: Lourdes
authors.initials: L
authors.lastname: Gómez-Rodríguez
mesh_terms: D001463:Barbiturates / Q000737:chemistry; D002384:Catalysis; D002470:Cell Survival / Q000187:drug effects; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity; D018360:Crystallography, X-Ray; D006367:HeLa Cells; D006801:Humans; D007477:Ions / Q000737:chemistry; D008968:Molecular Conformation; D009532:Nickel / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D013882:Thiosemicarbazones / Q000737:chemistry*
chemical_list: D001463:Barbiturates; D056831:Coordination Complexes; D007477:Ions; D013882:Thiosemicarbazones; D010984:Platinum; D010165:Palladium; D009532:Nickel; C032232:barbituric acid