Pyrazolylpropanoate Complexes of Palladium(II) Chloride

Abstract The syntheses of the new ligands 3‐(pyrazol‐1‐yl)methylpropanoate (L1) and 3‐(2,4‐dimethylpyrazol‐1‐yl)methylpropanoate (L2) and their complexation with palladium(II) have been investigated. In our hands L1 is best prepared by a Michael addition catalyzed by Cs 2 CO 3 and L2 by a catalyst‐ and solvent‐free reaction. Both L1 and L2 react with PdCl 2 (COD) to produce trans‐ PdCl 2 (L1) 2 ( 3 ) and trans‐ PdCl 2 (L2) 2 ( 4 ) respectively. The crystal structures of both new complexes have been determined. An isomerization has been observed when complex 4 is dissolved in CDCl 3 or CD 3 CN. Kinetic data indicate that this is an equilibrium that is first order in both directions. We suggest this may be due to the isomerization of the trans‐ to the cis ‐isomer. Their ease of preparation in nearly quantitative yields make the new ligands L1 and L2 potentially useful for further studies.