Palladium(II) and platinum(II) complexes with N1-hydroxyethyl-3,5-pyrazole derived ligands

Reaction of the ligands 2-(5-methyl-3-phenyl-1H-pyrazol-1-yl) ethanol (L1) and 2-(3-methyl-5-phenyl-1H-pyrazol-1-yl) ethanol (L2) with [MCl2(CH3CN)(2)] (M = Pd(II), Pt(II)) gave the complexes trans-[MCl2L2] (M = Pd(II) and Pt(II), L = L1, L2). The new complexes were characterised by elemental analyses, conductivity measurements, mass spectrometry, IR, H-1 and C-13{H-1} NMR spectroscopies. The crystal and molecular structures of the ligand L2 and the complexes trans-[PdCl2L2] (L = L1, L2) were resolved by X-ray diffraction. Both palladium complexes consisted on monomeric trans-[PdCl2L2] (L = L1, L2) species and molecular packing is determined by intermolecular hydrogen bonding interactions. The NMR spectra of the complexes [PdCl2L2] (L = L1, L2) in CDCl3 solution, is consistent with a very slow rotation of the pyrazolic ligands around the Pd-N bond, so that two conformational isomers can be observed in solution (syn and anti). Different behaviour was observed for complexes [PtCl2L2] (L = L1, L2), for which only the anti isomer was detected in CDCl3 solution at room temperature. (C) 2012 Elsevier B. V. All rights reserved.