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, 1H and 13C{1H} 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.

New complexes trans-[MCl2(L)2] (M = Pd(II), Pt(II)) with ligands 2-(5-methyl-3-phenyl-1H-pyrazol-1-yl)ethanol (L1) and 2-(3-methyl-5-phenyl-1H-pyrazol-1-yl)ethanol (L2) were prepared and characterised. The crystal structure of both palladium complexes consisted on monomeric trans-[PdCl2(L)2] (L = L1, L2) species; molecular packing being determined by intermolecular hydrogen bonding interactions. The NMR spectra of the complexes [PdCl2(L)2] (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). In the case of complexes [PtCl2(L)2] (L = L1, L2) only the anti isomer was observedFigure optionsDownload as PowerPoint slideHighlights
► Pd(II) and Pt(II) complexes with N1-hydroxyethyl-3,5-pyrazole derived ligands were prepared.
► Crystal structures of two new Pd(II) complexes were resolved by X-ray diffraction.
► Slow rotation of the pyrazolic ligands around the Pd–N bond was observed in solution.
► Intermolecular interactions define 3D supramolecular structure in the solid state.