Azo(xy) vs Aniline Selectivity in Catalytic Nitroarene Reduction by Intermetallics: Experiments and Simulations

Abstract

Intermetallic nanoparticles are promising catalysts in hydrogenation and fuel cell technologies. Much is known about the ability of intermetallic nanoparticles to selectively reduce nitro vs alkene, alcohol, or halide functional groups; less is known about their selectivity toward aniline vs azo or azoxy condensation products that result from the reduction of a nitro group alone. Because azo(xy)arenes bear promise as dyes, chemical stabilizers, and building blocks to functional materials but can be difficult to isolate, developing high surface area nanoparticle catalysts that display azo(xy) selectivity is desirable. To address this question, we studied a family of nanocrystalline group 10 metal (Pd, Pt)-and group 14 metal (Ge, Sn, Pb)-containing intermetallicsPd 2 Ge, Pd 2 Sn, Pd 3 Sn 2 , Pd 3 Pb, and PtSnin the catalytic reduction of nitroarenes. In contrast to monometallic Au, Pt, and Pd nanoparticles and ″random″ Pd x Sn 1 − x nanoalloys, which are selective for aniline, nanoparticles of atomically precise intermetallic Pd 2 Ge, Pd 2 Sn, Pd 3 Sn 2 , and PtSn prefer an indirect condensation pathway and have a high selectivity for the azo(xy) products. The only exception is Pd 3 Pb, the most active among the intermetallic nanoparticles studied here, which is instead selective for aniline. Employing a novel application of molecular dynamicsbased on machine learned potentials within a DeePMD frameworkto heterogeneous catalysis, we are able to identify key reaction species on the different types of catalysts employed, furthering our understanding of the unique selectivity of these materials. By demonstrating how intermetallic nanoparticles can be as active yet more selective than other more traditional catalysts, this work provides new physical insights and opens new opportunities in the use of these materials in other important chemical transformations and applications.

Phase Evolution, Polymorphism, and Catalytic Activity of Nickel Dichalcogenide Nanocrystals

“…In contrast, nanoparticles of multiple other atomically precise intermetallics containing a different structure type are selective to azoxyarene and azobenzene. 70 To probe this possibility, we tested pyrite NiS 2 and NiSe 2 nanocrystals as catalysts for the solution-phase hydrogenation of nitrobenzene (PhNO 2 ) (Scheme 4, see Methods). Under ambient conditions, gas chromatography−mass spectroscopy (GCMS) analysis shows that nitrobenzene is fully reduced with either catalyst within only 4 h of reaction (Figure 10, Table 3).…”

“…The speed, ease, and high selectivity of these reactions provide a positive contrast with other reported catalysts and conditions which, in some cases, result in incomplete conversion or have limited selectivities. 70 Interestingly, when a ca. 1:1 mixture of m-and p-NiSe 2 is used, conversion is only 89%, indicating that the presence of marcasite impurities can be detrimental to catalysis.…”

“…Many monometallic and alloyed nanoparticlesand a nanoparticulate intermetallic (Pd 3 Pb)containing an fcc structure are selective to aniline. In contrast, nanoparticles of multiple other atomically precise intermetallics containing a different structure type are selective to azoxyarene and azobenzene …”

Efficient Transfer Hydrodehalogenation of Halophenols Catalyzed by Pd Supported on Ceria

“…The Pd/CeO2 models were generated using a ML-derived potential based on DFT energetics. [63] [64] For details, see the Supporting Information (Section S1). Analysis of these MD simulations which statistically sample adsorption, desorption, and reaction processes over the supported Pd nanoclusters indicated that the dissociative adsorption of the substrates onto Pd is exergonic, confirming a facile first step of the reaction.…”

Phosphine Ligand Binding and Catalytic Activity of Group 10–14 Heterobimetallic Complexes

“…Another emerging application of heterobimetallic complexes supported by hetero-element pincers is their use as single-source precursors to intermetallic nanocrystals. − In a recent study, varying the monodentate donor ligands (phosphine or phosphite) bound to SES complexes leads to different nanocrystalline products upon thermolysis . This suggests that the reactivity of the heterobimetallic [EPd] core can be fine-tuned by ligand substitution .…”