Influence of substituents in the pyrazole pre-ligands on their reaction products with (Phen)Pd(OAc)2

The unique palladium(II) complexes, namely, (Phen)Pd((CF₃)₂pz)₂, (Phen)Pd(MeCF₃pz)₂, and [(Phen)Pd₂(μ-dmpz)₂(dmpz)(Hdmpz)](OAc)₂H, where (CF₃)₂pzH is 3,5-bis(trifluoromethyl)pyrazole, MeCF₃pzH is 3-methyl-5-trifluoromethylpyrazole, Hdmpz is 3,5-dimethyl-pyrazole, Phen is 1,10-phenanthroline, have been obtained by the reactions of (Phen)Pd(OAc)₂ with the corresponding free NH-pyrazoles. According to the X-ray data, in the mononuclear pyrazolate complexes the Pd^II atom has a square planar environment of nitrogen atoms of phenanthroline and two monodentate-bound pyrazolate anions. The binuclear pyrazolate-bridged complex is additionally stabilized by intramolecular hydrogen bonding of the terminal dmpz anion and Hdmpz.