LAUSR

Palladium acetate trimer, Pd3(OAc)6, is a common precursor for Pd nanoparticle synthesis and an important precatalyst for homogeneous catalysis reactions. Added ligands (L, e.g., phosphines) are well-known to dissociate the Pd3(OAc)6 trimer into Pd(OAc)2 monomers and form Pd(OAc)2(L)2 complexes. Despite the importance of the trimer dissociation and ligand–monomer binding thermodynamics on the properties of the resulting Pd complex, little is known about either reaction. Using a combination of isothermal titration calorimetry (ITC), X-ray absorption fine structure (XAFS), and 31P nuclear magnetic resonance (31P NMR) on trimer samples containing monomer impurities, we developed a methodology and a trimer–monomer ITC model to obtain the Gibbs free energy, enthalpy, and entropy for both reactions in toluene and quantify the monomer content. The results provide the following, previously inaccessible, quantitative insights on the reactions. Trioctylphosphine (TOP)-monomer binding reaction is enthalpically drive...