Sonogashira Couplings on the Surface of Montmorillonite-Supported Pd/Cu Nanoalloys

To explore the true identity of palladium-catalyzed Sonogashira coupling reaction, montmorillonite (MMT)-supported transition metal nanoparticles (MMT@M, M = Pd, Cu, Fe, and Ni) were prepared, characterized, and evaluated systematically. Among all MMT@M catalysts, MMT@Pd/Cu showed the highest activity, and it was successfully extended to 20 examples with 57%–97% yields. The morphology characterization of MMT@Pd/Cu revealed that the crystalline bimetallic particles were dispersed on a MMT layer as nanoalloy with diameters ranged from 10 to 11 nm. In situ IR analysis using CO as molecular probe and XPS characterization found that the surface of Pd/Cu particles consisted of both catalytic active sites of Pd(0) and Cu­(I). The experiments on the catalytic activities of MMT@M found that Pd/Cu catalyst system exhibited high activity only in nanoalloy form. Therefore, the Pd/Cu nanoalloy was identified as catalyst, on which the interatom Pd/Cu transmetalation between surfaces was proposed to be responsible for its synergistic activity

Privilege Ynone Synthesis via Palladium-Catalyzed Alkynylation of “Super-Active Esters”

A neat palladium-catalyzed alkynylation reaction was developed with “super-active ester” as the carbonyl electrophile, which provides a clean and efficient synthetic protocol for a broad array of ynone compounds under CO-, Cu-, ligand-, and base-free conditions. The superior activity of triazine ester was rationalized by the strong electron-withdrawing ability and the unique affinity of triazine on palladium. A mechanistic experiment clearly demonstrated that the N–Pd coordination of triazine plays a crucial role for the highly efficient C–O activation

Copper Complexes in Carbon Nanotubes as Catalysts for Thermal Decomposition of Energetic Oxidizers

Metal compounds exhibit high catalytic activities in solid propellants as burning rate catalysts (BRCs), while the bulk particles and the nanoparticles loaded onto the surfaces of carbon materials cannot effectively display their catalytic activities. For reducing particle aggregation and improving their catalytic efficiencies as BRCs, seven copper complexes (CuL2) were successfully encapsulated into the inner spaces of carbon nanotubes (CNTs) via ultrasonication in this study. These complexes include Cu(Sal)2 (Sal = salicylate), CuC2O4, Cu(NO3)2·3H2O, Cu(acac)2 (acac = acetylacetonate), [Cu(TMEDA)2](NO3)2 (TMEDA = tetramethylethylenediamine), [Cu(MIM)4](DCA)2 (MIM = 1-methylimidazole, DCA = dicyanamide), and [Cu(NMIM)4](DCA)2 (NMIM = 1-methyl-2-nitroimidazole). In addition, the structures of the CuL2@CNT nanocomposites were investigated using transmission electron microscopy, scanning electron microscopy, Brunauer–Emmett–Teller surface area analysis, X-ray photoelectron spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction. Moreover, the combustion catalytic performances of the nanocomposites in the thermal decomposition of ammonium perchlorate (AP), cyclotrimethylenetrinitramine (also known as RDX), and 1,1-diamino-2,2-dinitroethene were evaluated; these performances considerably affect the thermal degradation of AP and RDX. The 5 wt % Cu(acac)2@CNTs with outer diameters of 4–6 nm (L1) caused the peak temperature of AP to shift 92.8 °C toward left at the high-temperature decomposition stage, and the released heat increased by 1448.06 J g–1 compared to pure AP; the 5 wt % [Cu(NMIM)2](NO3)2/@CNT (L1) advanced the RDX peak temperature by 17.3 °C. Moreover, the thermal decomposition mechanism of RDX in the presence of Cu(acac)2@CNT (L1) was investigated via in situ solid FTIR and thermogravimetry–FTIR–mass spectrometry. The additive (CuL2@CNTs) accelerated the exothermic reaction of C–N bond breakage. This in turn reduced the endothermic reaction of the N–N bond cleavage in RDX, contributing to an increase in the heat released by RDX. Based on these results, a potential mechanism is proposed where RDX pyrolysis is catalyzed by the composites