Revealing the Strong Relationships between Ligand Conformers and Activation Barriers: A Case Study of Bisphosphine Reductive Elimination

Quantum chemical models of reaction pathways can provide deep insight into the inner workings of transition metal complexes. Often, these simulations have relied on atomistic models where a single or a few conformational isomers of the complex are investigated. This Article will show that, for bisphosphine Ni complexes used to forge C-C bonds, a large number of conformers must be studied to provide confidence that the overall model is meaningful. Not only do conformer effects modify particular reaction barriers, but often the lowest barrier reaction pathway proceeds from a conformer that is not the lowest energy conformer. This finding suggests that errors on the order of more than a few kcal/mol could be present in single-conformer studies. The particular reaction pathway and conformer preferences for a series of eight common Ni bisphosphine complexes will provide some guidance as to when the effects of the conformer will be large or small.