Synthesis and characterisation of palladium(II) and platinum(II) compounds containing pyrazole-derived ligands: crystal structure of [PdCl2(HL1)] (HL1 = 3-phenyl-5-(2-pyridyl)pyrazole)

Reaction of the ligands 3-phenyl-5-(2-pyridyl)pyrazole (HL1), 3,5-bis(2-pyridyl)pyrazole (HL2), 3-methyl-5-(2-pyridyl)pyrazole (HL3) and 3-methyl-5-phenylpyrazole (HL4) with [MCl2(CH3CN)2] (M = Pd(II), Pt(II)) or [PdCl2(cod)] gives complexes with stoichiometry [PdCl2(HL)2] (HL = HL1, HL2, HL3), [Pt(L)2] (L = L1, L2, L3) and [MCl2(HL4)2] (M = Pd(II), Pt(II)). The new complexes were characterised by elemental analyses, conductivity measurements, infrared and 1H NMR spectroscopies. The crystal and molecular structure of [PdCl2(HL1)] was resolved by X-ray diffraction, and consists of monomeric cis-[PdCl2(HL1)] molecules. The palladium centre has a typical square planar geometry, with a slight tetrahedral distortion. The tetra-coordinated metal atom is bonded to one pyridine nitrogen, one pyrazolic nitrogen and two chloro ligands in a cis disposition. The ligand HL1 is not completely planar.