Binding Energies of H2 and a Ligands to Stable Complexes

Solution calorimetric measurements on reactions of H2 complexes and their precursor complexes were first carried out by Hoff and coworkers on the original 

The enthalpy term for Eq. (7.1), H°, is -18.9 0.4 kcal/mol in toluene, and that in Eq. (7.2) is -9.5 0.5 kcal/mol under an H2 atmosphere. The difference in enthalpies corresponds to the enthalpy of H2 addition to W(CO)3(PCy3)2, which is exothermic by 9.4 0.9 kcal/mol. Note that these enthalpies are not the true binding energies because an agostic interaction is being displaced [Eq. (7.3)]. Thus the energy 

Another technique for measuring enthalpies of H2 addition (or loss) is variable-temperature NMR in systems showing equilibrium binding of H2 in solution.5-11 

Few measurements of binding energies of a ligands other than H2 have been made on stable complexes. NMR measurements as above show that reaction of Ph2SiH2 with an agostic Mo complex is energetically similar to that for the H2 

Binding Energies of H2 and Ligands to Thermally Unstable Metal Complexes 

---