Palladium versus Earth-abundant metals: comparisons from the synthetic and environmental perspectives for Suzuki–Miyaura cross-couplings and aminations

Direct comparisons are made using factual, published experimental results for two of the most commonly used cross-couplings that rely on either Pd or Ni (and in some cases, Cu, Co, and Fe) catalysis. Which metal in ligated form is best from both the synthetic and environmental perspectives for the intended bond formation is assessed comparing representative recent results for both Suzuki–Miyaura (SM) couplings and aminations. Several factors are considered, including: catalyst loadings, overall reaction efficiency, ligand availability, cost, residual metal expected in the products, energy invested, etc., and how these relate to the presumed benefits noted as the basis for shifting towards catalysis away from Pd using Earth-abundant metals (EAMs). For each type of coupling, a chart summarizing comparison data is provided, with the overall outcome leading to the same final conclusion.