A palladium nanoparticle implanted polymer membrane for reusable dip-catalysis of diverse C–C and C–heteroatom (O/S/N) coupling reactions

Abstract

The criteria for the development of a successful catalyst are simple yet cheap fabrication, high efficiency, stability, flexibility, straightforward recovery, reusability, and ease of scale-up. There are reports of palladium nanoparticle (PdNP)-based catalysts for performing carbon–carbon cross-coupling reactions, but the aforesaid criteria are rarely met in a single system. Moreover, a single catalyst system performing different types of C–C and C–heteroatom cross-coupling reactions is very rare. Herein, we achieved the above-mentioned criteria by using a reusable polymer-embedded Pd nanoparticle dip-catalyst membrane without any other ligands or additives under milder reaction conditions. The composite membrane was fabricated by simply depositing poly(4-vinyl pyridine) anchored PdNPs (average size 9.9 nm) onto a nylon-6 membrane followed by UV cross-linking. C–C bond formation reactions using diverse reagents (Suzuki–Miyaura, Heck, Sonogashira, Stille, Hiyama reactions) were achieved to give the desired products in high to excellent isolated yields, while C–X (X = N/O/S) bond formations were accomplished in moderate to good isolated yields. The turnover number (TON) and frequency (TOF) for the Suzuki–Miyaura cross-coupling reaction are calculated as ≥×10⁴ and 3.11 s⁻¹, respectively. The P4VP–PdNP dip-catalyst system was stable under the reaction conditions without significant leaching of Pd into the solution. The dip-catalyst membrane can be reused at least 10 times without losing any significant activity. The substrate scope for most of the cross-coupling reactions was tested, which indicates functional group tolerance and that the coupling reaction can take place with moieties having electron donating or withdrawing groups.