Thermodynamic hydricity, the free energy required for heterolytic cleavage of a metal-hydrogen bond, can provide insight into catalytic reactions. Two different computational methods for the calculation hydricity have been are compared: the potential-pKa method, in which hydricity is calculated by sum up the Gibbs free energy of pKa reaction and reverse of reduction potential reaction along with conversation of H+ to H-; and direct calculation, in which hydricity is calculated by simply calculating the Gibbs free energy of donation of H-. Hydricity values were calculated by computating the reduction potential and pKa values for a set of [Ir(Cp*)(bpy-R)H]+ (R = H, Me, OMe, COO-, COOMe) and a good linear correlation was found between experimental and computational data. A second method, direct calculation of the hydricity, was also applied to the [Ir(Cp*)(bpy-R)H]+ series, and it was found out that hydricities using direct calculation are ~16 kcal/mol higher than hydricities determined using the potential-pKa method. The methods were expanded to a new training set of transition metal hydride complexes (with known experimental hydricity values) and a near linear correlation with experimental values was found.

Hydricity calculation using computational methods: Potential-pKa method versus direct calculation

254th National Meeting (2017)

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