From waste electronic equipment to homogeneous gold catalysts Sean McCarthy 1 , D. Christopher Braddock 1 Angela Serpe 2,3 , James D. E. T. Wilton-Ely 1 1 Imperial College London, UK, 2 University of Cagliari, Italy, 3 (IGAG-CNR), Italy Waste electrical and electronic equipment (WEEE) is one of the fastest growing waste streams in the world and the majority of this material is currently still sent to landfill despite its precious metal content. 1 The secondary source raw material in this ‘urban mine’ has the potential to yield far more gold (e.g., 50-700 g/ton from printed circuit boards) 2 than that the amount typically obtained from primary gold mined ores or concentrates (1-10 3 g/ton), the production and processing of which relies on highly polluting and environmentally-damaging processes. 1-4 Along with these environmental factors, the unrelenting demand for gold and its limited availability in the earth’s crust lead to its high cost (£51 per gram, July 2022). This has led to the investigation of approaches that can valorise end-of-life WEEE using innovative, low-impact recovery processes, which are both economically and environmentally more sustainable than the established and unsustainable mining of gold from ore. 5 In response to these challenges, 6 we have investigated the catalytic activity of four gold(III) complexes obtained as recycling products from scrap SIM cards. By employing the recovery method developed by Deplano and Serpe et. al , 5 two coordinatively saturated cationic gold(III) complexes have been recovered from scrap SIM cards, and from them two novel gold(III) complexes were synthesised via a unique anion metathesis strategy. These complexes were investigated as homogeneous catalysts in a range of C-C bond forming reactions operating under varying mechanistic pathways, demonstrating the first four-coordinate cationic gold(III) precatalyst. The recyclability of these homogeneous catalysts has also been investigated, enhancing still further the sustainability of the process. These results demonstrate for the first time that molecular gold complexes derived from WEEE can be used in catalysis, providing an important application for material that would otherwise be sent to landfill. 7 References 1. World Economic Forum. A New Circular Vision for Electronics Time for a Global Reboot ; 2019 2. Nuss, P.; Eckelman, M. J. PLoS One 2014 , 9 (7), 1–12. Tuncuk, V. Stazi, A. Akcil, E. Y. Yazici, H. Deveci, Miner. Eng ., 2012 , 25 (1), 28–37. 3. Akcil, C. Erust, C. S. Gahan, M. Ozgun, M. Sahin, A. Tuncuk, Waste Manag ., 2015 , 45 , 258–271. 4. Deplano, M. L. Mercuri, L. Pilia, A. Serpe, M. Vanzi, European Patent EP1964936B1. 5. McCarthy, A. Lee, D. C. Braddock, A. Serpe, J. D. E. T. Wilton-Ely, Molecules , 2021 , 26 , 5217. 6. McCarthy, O. Desaunay, A. Lee, M. Hassatzky, A. J. P. White, P. Deplano, D. C. Braddock, A. Serpe and J. D. E. T. Wilton- Ely, ACS Sustainable Chem. Eng., 2022 , Submitted .
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