On the Sustainability of Palladium in Organic Synthesis: A Perspective

Ask any card-carrying organic chemist which metal reigns supreme today in synthetic organic chemistry and most, if not all, will quickly identify palladium as the clear winner. But this soft, silver-white metal is only one of six that make up the platinum group metals (pgms), which also include Ru, Os, Pt, Rh, and Ir. According to the ACS Green Chemistry Institute,1 Pd has “limited availability…”; the other five are also endangered, given their “rising threat from increased use.” In brief, they are, in one way or another, all at risk. And while neither Os nor even Ru is considered “precious” usually based on cost, both Pt and Pd are certainly “expensive”, while Ir, and especially Rh, are borderline prohibitive, typically being reserved for reactions where catalyst loadings must be very low. During the past few years, the price of Pd has jumped on occasion to >$3000/Troy ounce (vide infra), and even today remains more valued than is Au (<$2000/Troy ounce). What does this suggest regarding the prognosis for pgms even in the short term, let alone the prospects for long term availability? How can we continue today with a “business as usual” mentality, knowing that these particular resources on the planet are finite? Are we not already operating in crisis mode, if only on the basis of price, where palladium may provide, at least on paper, the solution to an important synthetic problem but its use in the lab is simply unaffordable? For many CMOs that make crucial intermediates, that time is already here. What now?