New (η3-Allyl)palladium Complexes with Pyridylpyrazole Ligands: Synthesis, Characterization, and Study of the Influence of N1 Substituents on the Apparent Allyl Rotation

The allylpalladium [Pd(η 3 -C 3 H 5 )(L)](BF 4 ) (L = L 1 ( 1 ), L 2 ( 2 ), L 3 ( 3 ), L 4 ( 4 )) complexes with pyridylpyrazole ligands 2-(5-phenyl-1 H -pyrazol-3-yl)pyridine (L 1 ), 2-(1-ethyl-5-phenyl-1 H -pyrazol-3-yl)pyridine (L 2 ), 2-(1-octyl-5-phenyl)-1 H -pyrazol-3-yl)pyridine (L 3 ), and 2-(5-phenyl-3-(pyridin-2-yl)pyrazol-1-yl)ethanol (L 4 ) were synthesized from the appropriate pyridylpyrazole ligand and [Pd(η 3 -C 3 H 5 )Cl] 2 in the presence of AgBF 4 . The cationic complex 1 was converted into the neutral complex 5 under basic conditions. These complexes were characterized, and the crystal and molecular structure of [Pd(η 3 -C 3 H 5 )(L 2 )](BF 4 ) ( 2 ) was resolved by X-ray diffraction. Also, we have studied the apparent allyl rotation, observed as H syn −H syn and H anti −H anti interconversions. The influences of the solvent, the traces of water, and the N1 substituent have also been studied.