Synthesis, X-ray crystal structure, and NMR characterisation of thiolate-bridged dinuclear Ni(II), Pd(II) and Pt(II) complexes of didentate ligands with NS-donor set Jordi Garcı ´a-Anto ´n a , Josefina Pons a, *, Xavier Solans b , Merce ` Font-Bardia b , Josep Ros a, * a Departament de Quı ´mica, Facultat de Cie `ncies, Universitat Auto `noma de Barcelona, 08193-Bellaterra-Cerdanyola, Barcelona, Spain b Cristal.lografia, Mineralogia i Dipo `sits Minerals, Universitat de Barcelona, Martı ´ i Franque `s s/n, 08028 Barcelona, Spain Received 29 January 2003; accepted 16 April 2003 Abstract Thiolate-bridged dinuclear nickel(II), palladium(II) and platinum(II) complexes with N -(2-mercaptoethyl)-3,5-dimethylpyrazole (Hmed), [MCl(med)] 2 (M/Ni (1), Pd (2), Pt (3)), have been synthesised and characterised by elemental analyses, conductivity, IR, electronic spectra and NMR spectroscopies. The crystal structure of 2 was determined by a single-crystal X-ray diffraction method. The structure consists of thiolate-bridged dinuclear units. Each Pd(II) atom is coordinated by a pyrazolic nitrogen, one chlorine and two bridging sulfur atoms. When the synthesis of complex 1 was carried out in acetonitrile and in the presence of oxygen, [NiCl 3 (Hdeds)] (4) was formed (deds /1,1?-(dithiodiethylene)bis(3,5-dimethylpyrazole)). The crystal structure of this complex was also determined by single-crystal X-ray diffraction method. The structure consists of nickel(II) ions coordinated by three chloride ions and one pyrazolic nitrogen atom. Ligand deds is the result of the oxidation of N -(2-mercaptoethyl)-3,5-dimethylpyrazole (Hmed). # 2003 Elsevier Science B.V. All rights reserved. Keywords: Nickel; Palladium; Platinum; Dinuclear; N,S ligands 1. Introduction The known tendency of thiolate ligands to give highly insoluble neutral complexes of polymeric nature has led to new synthetic strategies [1] and thus has enabled the obtaining of structural information on metal-thiolate complexes [2]. Discrete first-row transition-metal complexes featur- ing central M(m 2 -SR) x M cores (x /1  /3) have come under increased investigation in the past several years [3]. There are several M(m 2 -SR) x M type complexes [4], most of which have been studied in attempts to mimic the bonding, spectral and redox properties of bioinor- ganic compounds [1a,5,6,7]. The Ni(m 2 -SR) x Ni has attracted much attention to model the active site of the nickel-enzymes [8], in particular for the hydrogenases, metalloenzymes which catalyse H 2 /2H   /2e  . Only recently, however, it has been established that the active site contained a dime- tallic substructure [9]. Pt(m 2 -SR) x Pt complexes have been ascribed as anti- tumor drugs [10]. However, their inactivation is thought probably to be due to the bonding of platinum atoms to sulfur-containing biomolecules [11]. In recent years, we have studied and reported the synthesis and characterisation of ligands N -alkylamino- pyrazole [12], N -hydroxyalkylpyrazole [13], N -phosphi- nopyrazole [14] and more recently ligands containing pyrazolyl and thioether groups [15]. * Corresponding authors. Tel.:  /34-93-581 2895; fax:  /34-93-581 3101. E-mail address: josefina.pons@uab.es (J. Pons). Inorganica Chimica Acta 355 (2003) 87  /94 www.elsevier.com/locate/ica 0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0020-1693(03)00333-5