From recovered metal waste to high-performance palladium catalysts. Issue 24 (21st November 2017)

• Record Type: Journal Article
• Authors: Jantan, Khairil A.; Kwok, Chuek Yee; Chan, Kuang Wen; Marchiò, Luciano; White, Andrew J. P.; Deplano, Paola; Serpe, Angela; Wilton-Ely, James D. E. T.
• Is Part Of: Green chemistry. Volume 19:Issue 24(2017)
• Page Start: 5846
• Page End: 5853
• Publication Date: 2017-11-21
• Subjects: Environmental chemistry -- Industrial applications -- Periodicals; Environmental management -- Periodicals; 660
• DOI: 10.1039/c7gc02678a
• Languages: English
• ISSNs: 1463-9262

Abstract

Abstract : Molecular palladium complexes, recovered selectively from used catalytic converters, can be directly valorised as highly-active catalysts for C–H oxidative functionalisation. Abstract : The catalytic activity of a series of neutral and cationic, homo- and heteroleptic, mono- and bimetallic palladium(ii ) compounds based on dithiocarbamate and dithiooxamide S, S-donor ligands is described. High activity was observed in the regio- and chemo-selective C–H functionalization of benzo[ h ]quinoline to 10-alkoxybenzo[ h ]quinoline and 8-methylquinoline to 8-(methoxymethyl)quinoline in the presence of the oxidant PhI(OAc)2 . The best performance was found for [Pd(Me2 dazdt)2 ]I6 (Me2 dazdt = N, N ′-dimethyl-perhydrodiazepine-2, 3-dithione), [PdI2 (Me2 dazdt)] and [Pd(Cy2 DTO)2 ]I8 (Cy2 DTO = N, N ′-dicyclohexyl-dithiooxamide) which are all obtained directly as products of sustainable Pd-metal leaching processes used to recover palladium from scrap metal. These compounds provided almost quantitative yields under milder conditions (50 °C, 1–3 mol% Pd loading) and much shorter reaction times (1–3 h) than reported previously. These results illustrate how the complexes obtained from the selective and sustainable recovery of Pd from automotive heterogeneous Three Way Catalysts (TWC) can be employed directly in homogeneous catalysis, avoiding further metal recovery steps and valorising the metal complex itself in a 'circular economy' model.