(427a) Scaling Relations in Homogeneous Catalysis: Analyzing the Buchwald-Hartwig Amination Reaction

Scaling relations are a well-known concept in heterogeneous catalysis. It suggests that energies of the reaction intermediates binding to a catalyst are dependent on each other. Since the energies of reaction intermediates (and transition states) are interdependant, one needs to compute the energy of only one intermediate (called the descriptor) to evaluate the performance of a new catalyst. Scaling relations could be used to get the energies of the remaining reaction intermediates. Scaling relations reduce the computational cost.

The exploration of the utility scaling relation in homogeneous catalysis is far less reported. We have investigated the transferability of the concept of scaling relations to a homogeneous catalysis reaction known as the Buchwald−Hartwig amination (BHA) reaction. The reaction of PhBr with MeNH2 using 37 different Pd−L complexes (L = phosphine ligand) is studied, and scaling relations are established among the reaction intermediates and transition states. Using the scaling relations, we construct volcano plots, which is the plot of the log(rate) vs the descriptor intermediate energy. The insights from the volcano plots agree well with the experimental trends from the literature and give direction toward better catalyst design.