Nanowire Networks of Metal–Organosilicates as Reversible Pd(II) Reservoirs for Suzuki Coupling Reactions

Abstract

Formation of metallic palladium nanoclusters is an issue that hampers effective utilization of this precious metal in Suzuki−Miyaura and other cross-coupling reactions. In this regard, reversibility of shuttling between oxidative-state precatalysts and metallic-state acting catalysts is considered as a key for the design of Pd-based nanocatalysts. Herein, three-dimensional (3D) copper−organosilicate (Cu−OS) nanowire networks derived from 3-aminopropyl trimethoxysilane precursors have been demonstrated as an effective, reversible Pd(II) reservoir for Suzuki coupling reactions. In particular, the Pd ion-exchanged 3D nanowire networks exhibit excellent reactivity, stability, and recyclability, with no detectable formation of palladium nanoclusters and no perceptible loss of catalytic activity throughout 10 reaction cycles. A reversible Pd(II)−Pd(0)−Pd(II) shuttling between the solid-phase reservoir and liquid-phase coupling reaction was recognized through our extensive mechanistic investigations and material characterizations. High-throughput studies suggest that besides the decent recyclability, outstanding catalytic performance was due to the structural and compositional merits of the 3D nanowire networks. The scale of the overall macroscopic framework is in the micrometer range, which facilitates facile catalyst recovery. Meanwhile, the nanometer-scale 1D constituents offer high openness and accessibility for effective Pd shuttling. Chemically, the relatively weak alkylamine ligands circumvent the over-coordination issue commonly encountered by strong ligands and effectively prevent the formation of Pd nanoclusters. Compared with a number of state-of-the-art Pd-based catalysts, our 3D nanowire networks manifest excellent performance and recyclability simultaneously.

Single Solid Precursor-Derived Three-Dimensional Nanowire Networks of CuZn-Silicate for CO2 Hydrogenation to Methanol

“…Figures a–d and S3 show the TEM images of the time evolution of the nanowire growth. The observed dissolution–polycondensation process has been explained in the literature . Based on these results, a layered supramolecular assemblage of copper–organosilicate ( i.e.…”

“…Based on these results, a layered supramolecular assemblage of copper–organosilicate ( i.e. , Si–RNH 2 –Cu) was also proposed (Scheme d). ,,− …”

“…With the above Cu 2 O nanospheres and APTMS, a three-dimensional copper–organosilicate nanowire network (Si–RNH 2 –Cu) can be obtained (Figure e–h) . The interconnected nanowires possess a relatively small diameter of 20–30 nm, while the overall networks may span several to tens of micrometers.…”

“…In our recent study, we developed a versatile metal–organosilicate system, starting from Cu 2 O nanospheres and 3-aminopropyl trimethoxysilanes (APTMS, Scheme a–d). Due to the presence of its abundant alkylamine ligands, the material has been demonstrated as an ion-exchangeable metal reservoir for hosting metal contents in an atomically dispersed form . First, Cu + species is etched from the Cu 2 O template through amine-coordination and oxidized to soluble Cu 2+ (Scheme b); then, the polycondensation of APTMS molecules leads to the formation of copper–organosilicate nanowires (Scheme c), and eventually, the integration of the nanowire growth produced the highly accessible three-dimensional (3D) nanowire networks (Scheme d).…”

Novel Recyclable Pd/H-MOR Catalyst for Suzuki-Miyaura Coupling and Application in the Synthesis of Crizotinib

“…However, Pd/H-MOR did not exhibit an excellent catalytic performance when aryl chlorides were used as the substrate, even if the reaction times were extended to 8 hours (Table 3, entries [17][18][19][20]. The coupling reactions using aryl boronic acids were also investigated, and the coupling products were obtained in good yields, while the electron-releasing groups in aryl boronic acid gave higher yields compared to substrates bearing electron-withdrawing groups (Table 3, entries [21][22][23][24]. The Suzuki coupling reaction of heteroaryl bromide and phenylboronic acid was effective in optimized reaction conditions, producing the corresponding products (Table 3, entries 25,26).…”