The allylpalladium [Pd(η3-C3H5)(L)] (BF4) (L = L1 (1), L2 (2), L3 (3), L4 (4)) complexes with pyridylpyrazole ligands 2-(5-phenyl-1H- pyrazol-3-yl)pyridine (L1), 2-(1-ethyl-5-phenyl-1H-pyrazol-3-yl) pyridine (L2), 2-(1-octyl-5-phenyl)-1H-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(η3-C3H5)Cl]2 in the presence of AgBF4. 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(η3-C3H 5)(L2)](BF4) (2) was resolved by X-ray diffraction. Also, we have studied the apparent allyl rotation, observed as Hsyn-Hsyn and Hanti-Hanti interconversions. The influences of the solvent, the traces of water, and the N1 substituent have also been studied. © 2007 American Chemical Society.