Homogeneous Gold Catalysis Using Complexes Recovered from Waste Electronic Equipment

Abstract

Despite the greater awareness of elemental sustainability and the benefits of the circular economy concept, much waste electrical and electronic equipment (WEEE) is still destined for landfill. Effective methods for valorizing this waste within our society are therefore imperative. In this contribution, two gold(III) complexes obtained as recovery products from WEEE and their anion metathesis products were investigated as homogenous catalysts. These four recovery products were successfully applied as catalysts for the cyclization of propargylic amides and the condensation of acetylacetone with o-iodoaniline. Impressive activity was also observed in the gold-catalyzed reaction between electronrich arenes (2-methylfuran, 1,3-dimethoxybenzene, and azulene) and α,β-unsaturated carbonyl compounds (methyl vinyl ketone and cyclohexenone). These recovered compounds were also shown to be effective catalysts for the oxidative cross-coupling reaction of aryl silanes and arenes. When employed as Lewis acid catalysts for carbonyl-containing substrates, the WEEE-derived gold complexes could also be recovered at the end of the reaction and reused without loss in catalytic activity, enhancing still further the sustainability of the process. This is the first direct application in homogeneous catalysis of gold recovery products sourced from e-waste.

Recent Progress in Turning Waste into Catalysts for Green Syntheses

“…Interestingly, the residual undeposited solid e-waste still contained precious metals, which could be utilized in further recycling processes. McCarthy et al have recently demonstrated that catalyst recovery must not focus primarily on recovering the metal of interest, but that complexed metal ions recovered from e-waste can also be used as effective homogeneous catalysts for various chemical reactions [26]. The authors showcased this by extracting Au(III) with different complexing agents from old subscriber identity module (SIM) cards using a mild and efficient leaching method (Figure 1c).…”

Sequential Selective Dissolution of Coinage Metals in Recyclable Ionic Media

“…Utilization of (biomass-based) organic media for noble metal recycling [28][29][30][31][32][33][34][35][36][37][38] seems to offer a paradigm shift towards selective metal dissolution with enhanced sustainability (Figure 1). Recent examples of single noble metal selective dissolution include the use of specific ligands [39][40][41] or conditions.…”