31P NMR study of the stoichiometry, stability and thermodynamics of complex formation between palladium(II) acetate and bis(diphenylphosphino)ferrocene

The complexation reaction between palladium (II) acetate, and 1,1′-bis(diphenylphosphino)ferrocene, DPPF, was investigated in two different deuterated solvents CDCl3 and DMSO at various temperatures using 31P NMR spectroscopy. The exchange between free and complexed DPPF is slow on the NMR time scale and consequently, two 31P NMR signals were observed. At metal ion-to-ligand mole ratio larger than 1, only one 31P NMR signal was observed, indicating the formation of a 1:1 Pd2+–DPPF complex in solution. The formation constant of the resulting 1:1 complexes was determined from the integration of two 31P signals. The values of the thermodynamic parameters (ΔH, ΔS and ΔG298) for complexation were determined from the temperature dependence of stability constants. It was found that, in both solvents, the resulting complex is mainly entirely enthalpy stabilized and the ΔH compensates the TΔS contribution.