How a Single Electron Affects the Properties of the “Non-Superatom” Au₂₅ Nanoclusters

In this study, we successfully synthesized the rod-like [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]^<i>q</i> (<i>q</i> = +1 or +2) nanoclusters through kinetic control. The single crystal X-ray crystallography determined their formulas to be [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]­(SbF₆) and [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]­(SbF₆)­(BPh₄), respectively. Compared to the previously reported Au₂₅ coprotected by phosphine and thiolate ligands (i.e., [Au₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺), the two new rod-like Au₂₅ nanoclusters show some interesting structural differences. Nonetheless, each of these three nanoclusters possesses two icosahedral Au₁₃ units (sharing a vertex gold atom) and the bridging “Au–Se­(S)–Au” motifs. The compositions of the two new nanoclusters were characterized with ESI-MS and TGA. The optical properties, electrochemistry, and magnetism were studied by EPR, NMR, and SQUID. All these results demonstrate that the valence character significantly affects the properties of the “non-superatom” Au₂₅ nanoclusters, and the changes are different from the previously reported “superatom” Au₂₅ nanoclusters. Theoretical calculations indicate that the extra electron results in the half occupation of the highest occupied molecular orbitals in the rod-like Au₂₅⁺ nanoclusters and, thus, significantly affects the electronic structure of the “non-superatom” Au₂₅ nanoclusters. This work offers new insights into the relationship between the properties and the valence of the “non-superatom” gold nanoclusters

How a Single Electron Affects the Properties of the “Non-Superatom” Au₂₅ Nanoclusters

In this study, we successfully synthesized the rod-like [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]^<i>q</i> (<i>q</i> = +1 or +2) nanoclusters through kinetic control. The single crystal X-ray crystallography determined their formulas to be [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]­(SbF₆) and [Au₂₅(PPh₃)₁₀(SePh)₅Cl₂]­(SbF₆)­(BPh₄), respectively. Compared to the previously reported Au₂₅ coprotected by phosphine and thiolate ligands (i.e., [Au₂₅(PPh₃)₁₀(SR)₅Cl₂]²⁺), the two new rod-like Au₂₅ nanoclusters show some interesting structural differences. Nonetheless, each of these three nanoclusters possesses two icosahedral Au₁₃ units (sharing a vertex gold atom) and the bridging “Au–Se­(S)–Au” motifs. The compositions of the two new nanoclusters were characterized with ESI-MS and TGA. The optical properties, electrochemistry, and magnetism were studied by EPR, NMR, and SQUID. All these results demonstrate that the valence character significantly affects the properties of the “non-superatom” Au₂₅ nanoclusters, and the changes are different from the previously reported “superatom” Au₂₅ nanoclusters. Theoretical calculations indicate that the extra electron results in the half occupation of the highest occupied molecular orbitals in the rod-like Au₂₅⁺ nanoclusters and, thus, significantly affects the electronic structure of the “non-superatom” Au₂₅ nanoclusters. This work offers new insights into the relationship between the properties and the valence of the “non-superatom” gold nanoclusters

The Key Gold: Enhanced Platinum Catalysis for the Selective Hydrogenation of α,β-Unsaturated Ketone

AuPt alloy nanoparticles (NPs) were facilely synthesized with oleylamine as the stabilizing ligand and characterized by high-resolution transmission electron microscopy, powder X-ray diffraction, inductively coupled plasma-atomic emission spectrometer analysis, and so on. In addition, the AuPt alloys supported by the nano CeO₂ exhibit high selectivity and efficiency in hydrogenation of benzylidene acetone under ambient temperature and pressure. By analyzing the catalytic performance over the NPs with different Au:Pt compositions, we found that the TON_Pt values (based on the number of Pt atoms) vary in the same trend with the change of conversion. Despite that gold itself shows no catalytic activity, the improved conversion and TON_Pt with the alloy catalysts clearly show the promotion effect of gold on the catalytic activity of the platinum. The inactive metal significantly improves the catalytic activity of active metal, which shows that the AuPt alloy exhibits an interesting synergistic effect

Synthesis and Structure of Self-Assembled Pd₂Au₂₃(PPh₃)₁₀Br₇ Nanocluster: Exploiting Factors That Promote Assembly of Icosahedral Nano-Building-Blocks

The essential force of self-assembly in the nanocluster range is not intrinsically understood to date. In this work, the synergistic effect between metals was exploited to render the self-assembly from the icosahedral M₁₃ (M = Pd, Au) nano-building-blocks. Single-crystal X-ray diffraction analysis revealed that the two Pd₁Au₁₂ icosahedrons were linked by five halogen linkages, and the assembled structure was determined to be Pd₂Au₂₃­(PPh₃)₁₀Br₇. The finding of Au–halogen linkages in the rod-like M₂₅ nanoclusters has not been previously reported. Furthermore, the calculations on Hirshfeld charge analysis were performed, which implied that the reduced electronic repulsion (induced by the synergistic effect of Pd and Au metals) between two icosahedral units promoted the assembly. This study sheds light on the deep understanding of the essential force of self-assembly from icosahedral nano-building-blocks

Pd–Ni Alloy Nanoparticles as Effective Catalysts for Miyaura–Heck Coupling Reactions

In this work, Pd–Ni alloy nanoparticles (NPs) were produced by a facile and efficient one-pot synthetic strategy in the presence of oleylamine (OAm) and triphenylphosphine (TPP). Transmission electron microscopy (TEM), energy-dispersive spectrometry (EDS) mapping, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and X-ray diffraction (XRD) were used to investigate the structure of Pd–Ni alloy NPs, which demonstrated that the as-prepared alloy NPs possessed uniform sizes and tunable compositions. Importantly, we found that TPP could affect the morphology of the Pd–Ni alloy. When TPP was absent from the reaction, the morphology of the Pd–Ni alloy was not uniform. In addition, the as-prepared Pd–Ni alloy NPs showed conspicuous composition-dependent catalytic activities for the Miyaura–Heck reaction. In the series of the Pd–Ni alloy NPs, Pd₁Ni₁ has an excellent effect for the Miyaura–Heck reactions. Furthermore, the Pd–Ni alloy NPs were also effective for different substrates in the Miyaura–Heck reactions. Compared to pure palladium, the Pd–Ni alloy NPs as the catalysts show better catalytic activity, selectivity, and stability

A Robust and Efficient Pd₃ Cluster Catalyst for the Suzuki Reaction and Its Odd Mechanism

The palladium-catalyzed Suzuki–Miyaura coupling reaction is one of the most versatile and powerful tools for constructing synthetically useful unsymmetrical aryl–aryl bonds. In designing a Pd cluster as a candidate for efficient catalysis and mechanistic investigations, it was envisaged to study a case intermediate between, although very different from, the “classic” Pd(0)­L<i>_n</i> and Pd nanoparticle families of catalysts. In this work, the cluster [Pd₃Cl­(PPh₂)₂(PPh₃)₃]⁺[SbF₆]⁻ (abbreviated <b>Pd</b>_<b>3</b><b>Cl</b>) was synthesized and fully characterized as a remarkably robust framework that is stable up to 170 °C and fully air-stable. <b>Pd</b>_<b>3</b><b>Cl</b> was found to catalyze the Suzuki–Miyaura C–C cross-coupling of a variety of aryl bromides and arylboronic acids under ambient aerobic conditions. The reaction proceeds while keeping the integrity of the cluster framework all along the catalytic cycle via the intermediate <b>Pd</b>_<b>3</b><b>Ar</b>, as evidenced by mass spectrometry and quick X-ray absorption fine structure. In the absence of the substrate under the reaction conditions, the <b>Pd</b>_<b>3</b><b>OH</b> species was detected by mass spectrometry, which strongly favors the “oxo-Pd” pathway for the transmetalation step involving substitution of the Cl ligand by OH followed by binding of the OH ligand with the arylboronic acid. The kinetics of the Suzuki–Miyaura reaction shows a lack of an induction period, consistent with the lack of cluster dissociation. This study may provide new perspectives for the catalytic mechanisms of C–C cross-coupling reactions catalyzed by metal clusters