The nickel phosphides have garnered increasing attention as an excellent catalytic site in the fields of electrocatalysis and hydrotreating, but their application in organic synthesis remains infrequent. In this study, ammonium phosphate and nickel chloride were employed as the doping sources for the first time to synthesize the Ni-based ZIF-8 precursor via the host–guest method. Subsequently, the precursor was pyrolyzed to obtain Ni2P nanoparticles (NPs) supported on N, P co-doped carbon. The composite materials exhibit elevated metal loading and effective dispersion due to the synergistic combination of phosphorus and nickel. Specifically, compared with Ni-NC, the optimal Ni2P-NCP-1 exhibits enhanced catalytic activity in the α-alkylation of arylacetonitriles with alcohols using KOH as the base. It shows a wide broad substrate scope at 140 °C for 12 h in n-octane using a hydrogen borrowing strategy. Through characterizations and mechanistic studies, it has been discovered that the introduction of P source not only provides more basic sites on carbon matrix but also leads to the formation of Ni2P NPs, which facilitates the catalytic efficiency by modifying the electronic structure of Ni. Compared with the metallic Ni species, the synergistic effect between Ni2P and acid-basic sites significantly influences the dehydrogenation of alcohols to generate Ni–H species. This study successfully achieves simultaneous phosphating of both the metal and support, and it also demonstrates that the N2P-NCP-1 catalyst has significant potential in the heterogeneous organic transformation field.
The development of highly efficient and recyclable bifunctional photoredox catalysts is extremely promising for organic synthesis. In this study, a novel kind of bifunctional metal-organic framework (MOF) based catalysts were prepared through the in-situ incorporation of the L -proline moiety into the MOF network and followed by the anchoring of dye molecules via a solvothermal process. These catalysts exhibited versatile catalytic activity in the visible light triggered α -alkylation of aldehydes and cross-dehydrogenative coupling reactions between N -aryl tetrahydroquinolines and ketones. The control experiments revealed enhanced synergy existed between the two kinds of catalytic active centers confined in the porous framework, resulting in significantly enhanced catalytic activities while maintaining comparable enantioselectivities to the corresponding homogeneous catalytic systems. Furthermore, the bifunctional catalysts showed high stability and reusability over five consecutive cycles with only a slight decrease in activity. Based on the experimental results, a plausible reaction mechanism over the present bifunctional catalyst was proposed.
Six tridentate NNN ligand precursors derived from 2-(pyridin-2-yl)benzo[d]thiazole(PBT) with different linkers, PBT NN X N (X = NH, NMe, O, S) ( 1a – 1f ), have been successfully prepared. The electronic properties of PBT NN X N ligands are well tunable by differing linkers between PBT skeleton and the pyridine ring, and/or by introducing electron-donating/withdrawing groups on the pyridine ring (R = OMe or F). The ligand precursors and representative complexes Ru ( PBT NN NH N )Cl 2 (PPh 3 ) ( 2a ), Ru ( PBT NN NMe N )Cl 2 (PPh 3 ) ( 2b ), and Ru ( PBT NN S N )Cl 2 (PPh 3 ) ( 2f ) have been characterized by NMR spectroscopy, high-resolution mass spectroscopy, and Fourier transform infrared (FT-IR). The molecular structures of 1f , 2a , and 2f have been determined by X-ray diffraction study. The results indicate that PBT NN NH N ligand in the complex presented coplanar with two five-membered chelating rings. It should be noted that 2a featuring a NH group exhibits superior performance compared to those with other linkers (such as NMe, O, or S). A variety of heterocyclic and aromatic nitriles with aromatic and aliphatic alcohols have been explored in α -alkylation for good to excellent yields. Based on kinetic experiments and mechanistic studies, a proposed mechanism was put forward. Ru-H species and benzaldehyde, which was oxidized from benzyl alcohol, were detected in the catalytic cycle.
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