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

Heterobimetallic complexes have attracted much interest due to their broad range of structures and reactivities as well as unique catalytic abilities. Additionally, these complexes can be utilized as single-source precursors for the synthesis of binary intermetallic compounds. An example is the family of bis(pyridine-2-thiolato)dichloro-germanium and tin complexes of group 10 metals (Pd and Pt). The reactivity of these heterobimetallic complexes is highly tunable through substitution of the group 14 element and the neutral ligand bound to the transition metal. Here, we study the binding energies of three different phosphorous-based ligands, PR3 (R = Bu, Ph, and OPh) by density functional theory and restricted Hartree–Fock methods. The PR3 ligand-binding energies follow the trend of PBu3 > PPh3 > P(OPh)3, in agreement with their sigma-bonding ability. These results are confirmed by ligand exchange experiments monitored with 31P NMR spectroscopy, in which a weaker binding PR3 ligand is replaced with a stronger one. Furthermore, we demonstrate that the heterobimetallic complexes are active catalysts in the Negishi coupling reaction, where stronger binding PR3 ligands inhibit access to an active site at the metal center. Similar strategies could be applied to other complexes to better understand their ligand-binding energetics and predict their reactivity as both precursors and catalysts."This is a manuscript of an article published as Daniels, Carena L., Eunbyeol Gi, Benjamin A. Atterberry, Rafael Blome-Fernández, Aaron J. Rossini, and Javier Vela. "Phosphine Ligand Binding and Catalytic Activity of Group 10–14 Heterobimetallic Complexes." Inorganic Chemistry 61, no. 18 (2022): 6888-6897. DOI: 10.1021/acs.inorgchem.2c00229. Copyright 2022 American Chemical Society. Posted with permission. DOE Contract Number(s): AC02-07CH11358

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

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─Pd2Ge, Pd2Sn, Pd3Sn2, Pd3Pb, and PtSn─in the catalytic reduction of nitroarenes. In contrast to monometallic Au, Pt, and Pd nanoparticles and ″random″ PdxSn1 – x nanoalloys, which are selective for aniline, nanoparticles of atomically precise intermetallic Pd2Ge, Pd2Sn, Pd3Sn2, and PtSn prefer an indirect condensation pathway and have a high selectivity for the azo(xy) products. The only exception is Pd3Pb, 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.This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in The Journal of Physical Chemistry C, copyright © American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/acs.jpcc.1c08569. DOE Contract Number(s): AC02-07CH11358. Posted with permission