Pyrazolic palladium compounds containing alcohol functionality: hindered rotation around Pd-N bond

Reactions of the ligands 1-hydroxymethyl-3,5-dimethylpyrazole (HL1), 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (HL2) and 1-(3-hydroxypropyl)-3,5-dimethylpyrazole (HL3) with [PdCl2(CH3CN)(2)] lead to trans-[PdCl2(HL)(2)] complexes. The ligands are coordinated to the Pd(II) by a N atom of the pyrazolic ring in a trans disposition. Two chlorides complete the environment of the metallic atom. These Pd(II) complexes were characterised by elemental analyses, conductivity measurements and IR, H-1 and C-13 NMR spectroscopies and X-ray diffraction. The NMR study of the complexes is consistent with a very slow rotation of ligands around the Pd-N bond, so that two conformational isomers can be observed in solution. The crystal structures of [PdCl2(HL)(2)] (HL = HL1, HL2) complexes are described. These complexes react with AgNO3 to give [Pd(NO3)(HL)(2)]NO3 compounds. (C) 2002 Elsevier Science B.V. All rights reserved.