Measuring or predicting metal-ligand bond energies with high accuracy remains a challenge, yet the routine ability to do so would clearly be a powerful tool in, for example, catalyst design. We have conducted a combined theoretical and experimental study on the thermodynamics of ligand binding to (PCP)Ir (PCP = ?3-C6H3-2,6-(CH2PtBu2)2), (PCP)Ir(H)(H) and (PCP)Ir(H)(Cl) complexes. The ligands feature P-, S- and N-donor atoms as well as various olefins and present a wide spectrum of electronic and steric effects. The relative binding free energies have been determined and, in selected cases, individual enthalpy and entropy contributions have also been derived. The ligands are adding to sterically crowded Ir-metal fragments; thus, the measured binding energies reflect a delicate balance of covalent and non-covalent interactions. Calculated binding energies using DFT show a strong dependence on the selected exchange-correlation functional with superior performance exhibited by functionals, which incorporate long-range interactions.

Thermodynamics of ligand binding to (PCP)Ir complexes: Experiment and DFT calculations

244th National Meeting (2012)

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