Affordable and Clean Energy (SDG 7), Responsible Consumption and Production (SDG 12)
From waste to wonder: palladium recovery product catalyze C-H Functionalization and C-N Bond Formation Khairil A. Jantan 1,3* , Angela Serpe 2 , James D. E. T. Wilton-Ely 3 1 Faculty of Applied Sciences, Universiti Teknologi MARA (UiTM), Shah Alam 40450, Malaysia, 2 Department of Civil and Environmental Engineering and Architecture (DICAAR), INSTM Unit, University of Cagliari, Via Marengo 2, 09123 Cagliari, Italy, 3 Department of Chemistry, Imperial College, Molecular Sciences Research Hub, White City Campus, London W12 0BZ, UK E-mail: khairil0323@uitm.edu.my Three-way catalysts (TWCs) are frequently employed in automobiles to mitigate exhaust emissions from internal combustion engines. TWCs lose catalytic efficiency after 8–10 years, requiring replacement and producing plenty of spent catalyst material.1 The material contains precious metals like palladium, making recycling possible. A simple and cost-effective method using TBAI and I2 has been shown to synthesize [N n Bu 4 ]2[Pd 2 I 6 ] with high yield and purity from the TWCs model.2 The present work provides evidence that the [N n Bu 4 ]2[Pd 2 I 6 ] can be transformed into PdI 2 (dppf) by a simple ligand-exchange method. The oxidative functionalization of benzo[ h ]quinoline and 8-methylquinoline demonstrated significant catalytic activity using [N n Bu 4 ]2[Pd 2 I 6 ] and PhI(OAc)2 as the oxidant under milder conditions (50 °C, 1–2 mol% Pd loading) and shorter reaction periods (2 hours) than literature values. The catalyst was also highly reusable and effective across multiple reaction cycles, boosting its sustainability. Notably, both [N n Bu 4 ]2[Pd 2 I 6 ] and PdI 2 (dppf) have demonstrated efficacy in Buchwald-Hartwig amination processes. The Design of Experiments (DoE) approach optimizes utilizing palladium loading between 1-2 mol% and dppf concentration from 3-6 mol% in a bioderived solvent (CPME), which presents a more environmentally friendly alternative to conventional amination methods. The findings highlight the potential of developing more sustainable catalytic processes by recycling palladium from spent TWCs. Key words: palladium; recovered metals; C-H functionalization; C-N amination; sustainability. References 1. Jantan, K. A., Ekart, G., McCarthy, S., White, A. J., Braddock, D. C., Serpe, A., & Wilton-Ely, J. D., Catalyst . 2024, 14, 295. 2. Cuscusa, M., Rigoldi, A., Artizzu, F., Cammi, R., Fornasiero, P., Deplano, P., Marchiò, L. and Serpe, A., ACS Sustainable Chem . Eng . 2017, 5, 359-4370.
Organic Transformation
Palladium Recovery
C-H Functionalization
Pd
I 2 [NBu 4 ]I
[Pd]
96% based on Pd content
H
OR
RT
ROH PhI(OAc) 2
24 h
decon- strution
milling
Ph 2 P
, CH
, CH(CH
, CH
2
R = CH 3
2 CF 3
2 CH 3
3 ) 2
I
I
I
I
Ligand substitution 2 dppf
Pd
Pd
Pd
Fe
C-N Amination
I
I
I
I
P Ph 2
2[N n Bu
+ H 2 N
4 ]
R'
R
X
spent TWC
n Bu
PdI 2 (dppf)
4 ] 2 [Pd 2 I 6 ]
[N
manufacture and use
H N
chemical reduction
heat or
R'
R
Pd
X = Br, I
Pd metal recovery
P73
© The Author(s), 2025
Made with FlippingBook Learn more on our blog