¬The impact of earth-abundant metals as a replacement for Pd in cross coupling reactions

Abstract

Substitution of one metal catalyst for another is not straightforward as simply justifying this change based on the availability and/or cost of the metals. A life cycle-like assessment was performed leading to the conclusion that the commonly held view that use of earth-abundant metals (and in this case study, Ni) are replacements for palladium most notably in cross coupling reactions, and Suzuki-Miyaura couplings, in particular, is an incomplete analysis of the entire picture. This notion can be misleading, and unfortunately derives nowadays mainly from the standpoint of cost, and to some degree, the relative natural abundance and mining impact of each metal. However, a more realistic appreciation emerges when several additional reaction parameters involved in the couplings are considered. Such an analysis unequivocally points to the major impact on climate change brought about by use of organic solvents, while the metals actually play subordinate roles in terms of CO2-release into the environment. Clearly, this study reveals that several factors contribute in various ways to the overall carbon footprint. Hence, a far more detailed analysis is required than that typically being utilized!