Guideline for Elucidating Catalysts

In the last decades, numerous efforts have been made to replace metal catalysts with cheaper and earth-abundant alternatives or the complete exclusion of metals in cross-coupling reactions, maintaining high efficiency of the target transformation. However, follow-up studies often revealed the role of metal impurities in the catalytic process. Thus, active metal impurities lead to mechanistic misinterpretations, could initiate erroneous research directives, and can lead to severe reproducibility problems. Milestone precedents of impurity effect in cross-coupling reactions are well documented in the literature. Interestingly, this fallacy has occurred repeatedly over the years due to the lack of thorough mechanistic studies and the appropriate research study scheme for identifying the impurity effect. Herein, we propose a guideline elucidating the real catalyst of future catalytic transformations that could eliminate mechanistic misinterpretation and help exclude the role of impurities in novel catalytic processes. Although this guideline mainly focuses on problems related to trace transition metals, it also offers the base for more general catalyst research.