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)Ln and Pd nanoparticle families of catalysts. In this work, the cluster [Pd3Cl(PPh2)2(PPh3)3]+[SbF6]− (abbreviated Pd3Cl) was synthesized and fully characterized as a remarkably robust framework that is stable up to 170 °C and fully air-stable. Pd3Cl 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 Pd3Ar, as evidenced by mass spectrometry and quick X-ray absorption fine structure. In the absence of the substrate under the reaction conditions, the Pd3OH 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.Keywords: catalysis; C−C cross-coupling; mechanism of Pd-catalyzed reaction; metal cluster; Suzuki−Miyaura reaction;

Engineering the surface ligands of metal nanoclusters is critical for tuning their sizes, structures and properties at the atomic level. Herein, we report the synthesis and total structure determination of [Ag32(Dppm)5(SAdm)13Cl8]3+ and [Ag45(Dppm)4(S-But)16Br12]3+ (where Dppm = bis(diphenyphosphino)methane, HSAdm = 1-adamantanethiol and HS-But = tert-butyl mercaptan). The compositions of these two silver nanoclusters are determined by single-crystal X-ray diffraction (SC-XRD) and X-ray photoelectron spectroscopy (XPS), respectively. Remarkably, the asymmetric distribution of the three types of ligands (thiolate, phosphine, and halogen) on the cluster surface is responsible for the chirality of the clusters. It is worth noting that these findings demonstrate the key principles of ligand-shell anchoring for the tri-ligand protected silver clusters. Our work will offer further insights into the synthesis of chiral metal clusters by tailoring the surface ligands.

ZnO-Au25 nanocomposites were synthesized by doping Au25 nanoclusters into the porous ZnO nanospheres. It was notable that the ultrasmall Au25 nanoclusters possessed uniform sizes and fine dispersibility on the porous ZnO supports. A considerable correlation between the loading of Au25 nanoclusters and the photocatalytic activity was found. Compared with the pure ZnO nanospheres, the ZnO-Au25 nanocomposites exhibited more efficient photocatalytic activity in terms of degradation of Rhodamine B (RhB) in an aqueous solution. In addition, the possible photocatalytic mechanisms are discussed in this work. This strategy may be helpful for preparing other novel hybrid nanocomposites with well-defined structures and superior performances.

We report the X-ray crystallographic structure of an 18-metal atom Au–Ag bimetallic nanocluster (NC) formulated as [Au15Ag3(SC6H11)14]. This NC consists of a Au6Ag3 bi-octahedral kernel, which is built up by two octahedral Au3Ag3 units through sharing one Ag3 triangular face. The [Au15Ag3(SC6H11)14] can be viewed as a core–shell structure with the doped Ag atoms as the core and Au atoms as the shell. Detailed analyses by UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements clearly show distinct differences in the electronic structure between [Au15Ag3(SC6H11)14] and the homometal [Au18(SC6H11)14] NC. This study contributes to the deep understanding on bimetallic nanoclusters.

In this work, we have successfully synthesized ultrasmall Cu2O nanocrystals with uniform sizes through a solution-based method. By virtue of the ideal Cu2O building blocks, 2D or 3D Cu2O superstructures can be easily achieved by tailoring the assembly process. The results indicate that diethyl carbonate (DEC) plays a crucial role for controlled self-assembly of Cu2O nanoparticles into a range of superstructures. Interestingly, the aggregative growths of Cu2O nanocrystals in the self-assembly process are accompanied by oriented attachment and Ostwald ripening. Furthermore, Cu2O and Cu2O–Au 3D colloidal spheres can be also obtained by an emulsion-based bottom-up self-assembly strategy. The results show that, compared with pure Cu2O nanospheres, the as-obtained Cu2O–Au nanospheres exhibit remarkable photocatalytic activities in the photodegradation of methyl orange (MO).

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 simple and efficient method for the synthesis of ultrasmall Pd nanoclusters (NCs) has been developed. The as-obtained Pd NCs displayed uniform size with an average diameter of 1.8±0.2 nm. The ultrasmall Pd NCs and carbon nanotubes (CNTs)-supported Pd NCs also showed outstanding catalytic activity for nitrobenzene reduction and Suzuki coupling reactions. Notably, the reactions were conducted under mild conditions with high yield and selectivity.

Unique lotus-rootlike Au-ZnO hybrid structures were obtained by controlling the deposition of pre-synthesized Au nanocrystals onto the surfaces of as-obtained ZnO structures. ZnO with lotus-rootlike structures was first prepared through a hydrothermal process. We also investigated the effects of various Au contents on the photocatalytic activities in detail. Notably, compared to the pure ZnO component, these resulting lotus-root-like Au-ZnO nanostructures with the appropriate amounts of Au content exhibited better photocatalytic efficiency.

In this article, we present a facile, direct, synthetic approach of preparing monodisperse [Au25(SePh)18]− nanoclusters in high yield. In this synthetic approach, two-phase Brust-Schiffrin method is used. Both PhSeH and NaBH4 should be added drop-wise to the solution of Au (III) at the same time. The formula and molecular purity of [Au25(SePh)18]−TOA+ clusters are characterized by MALDI-TOF mass spectrometry, NMR and TGA analysis. Furthermore, some critical parameters to obtain pure [Au25(SePh)18]−TOA+ are identified, including the NaBH4-to-Au ratio, the selenolate-to-Au ratio and the temperature. The facile, direct, high yield synthetic method can be widely applied in the theoretical research of Au clusters protected by selenol.

A simple and efficient solution-based method for the synthesis of Pd-Ni bimetallic nanoparticles (NPs) has been developed. A series of Pd-Ni bimetallic NPs were readily achieved by reduction of PdCl2 and Ni(acac)2 (acac = acetylacetonate) in the presence of oleylamine (OAm), oleic acid (OA) and benzyl alcohol. Furthermore, by using high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectrometry (EDS) mapping and X-ray diffraction (XRD), we demonstrate that the as-prepared Pd-Ni bimetallic NPs have core-shell structures with a Pd-rich core and a Ni-rich shell. In addition, the as-obtained Pd-Ni bimetallic NPs with varying compositions show excellent catalytic activities in the Miyaura-Suzuki reaction. When the nickel molar percentage was 0.23 to 0.65, the conversion with the as-obtained Pd-Ni bimetallic catalysts was above 90%. It is believed that this strategy can be employed to produce a variety of other well-defined core-shell type multimetallic nanostructures.

In this work we are inspired to explore gold nanoclusters supported on mesoporous CeO2 nanospheres as nanocatalysts for the reduction of nitrobenzene. Ultrasmall Au nanoclusters (NCs) and mesoporous CeO2 nanospheres were readily synthesized and well characterized. Due to their ultrasmall size, the as-prepared Au clusters can be easily absorbed into the mesopores of the mesoporous CeO2 nanospheres. Owing to the unique mesoporous structure of the CeO2 support, Au nanoclusters in the Au@CeO2 may effectively prevent the aggregation which usually results in a rapid decay of the catalytic activity. It is notable that the ultrasmall gold nanoclusters possess uniform size distribution and good dispersibility on the mesoporous CeO2 supports. Compared to other catalyst systems with different oxide supports, the as-prepared Au nanocluster–CeO2 nanocomposite nanocatalysts showed efficient catalytic performance in transforming nitrobenzene into azoxybenzene. In addition, a plausible mechanism was deeply investigated to explain the transforming process. Au@CeO2 exhibited efficient catalytic activity for reduction of nitrobenzene. This strategy may be easily extended to fabricate many other heterogeneous catalysts including ultrasmall metal nanoclusters and mesoporous oxides.