2019 Fiscal Year Annual Research Report
パラジウム－希土類金属間化合物ナノ粒子による炭素―炭素クロスカップリング反応
| Project/Area Number |
18F18361
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
細野 秀雄 東京工業大学, 元素戦略研究センター, 特命教授 (30157028)
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| Co-Investigator(Kenkyū-buntansha) |
YE TIANNAN 東京工業大学, 元素戦略研究センター, 外国人特別研究員
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| Project Period (FY) |
2018-10-12 – 2021-03-31
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| Keywords | Rare-earth elements / Low work function / High carrier density / Intermetallic electride / Pd系不均一触媒 / Negatively charged active sites / Suzuki cross-coupling reactions |
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| Outline of Annual Research Achievements |
We successfully designed and prepared an intermetallic electride material Y3Pd2. It exhibited extreme high catalytic activities and excellent stability for Suzuki cross-coupling reactions, which was much higher than Pd metals and other commercial conventional Pd based supported catalysts. Mechanistic studies demonstrated that negatively charged Pd sites induce electron injection into the antibonding orbitals of C-X (X = I, Br), significantly promoting the activation of aryl halides, which is the rate-determining step for the investigated Suzuki cross-coupling reactions. Since Pd active sites were stabilized through ionic and metallic bonding within the intermetallic lattice, excellent reusability was also achieved on these intermetallic catalysts.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
I think our research progress beyond the original plan.
Besides Y3Pd2, we also developed a series of Pd-based intermetallic compounds such as Y3Pd, Y3Pd4 and YPd3. It is noted that their Pd active sites were also negatively charged with low work function features. We found that all of Y3Pd, Y3Pd4, and YPd3 show good activities for Suzuki coupling reaction and their calculated TOFs are comparable to that of Y3Pd2, and nearly one order of magnitude higher than pure Pd metal. Kinetic study also demonstrated that these Y-Pd binary catalysts exhibit the similar activation energies for the Suzuki coupling reactions. Moreover, the reaction protocol was further extended to various aryl halides and boronic acids to verify the scope and activity of Suzuki coupling reactions catalyzed. All of the substituted iodobenzenes and bromobenzenes with varied functional groups could be converted to the corresponding coupled products in high yields
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| Strategy for Future Research Activity |
In the next plan, we want to realize nano-crystallization of intermetallics so as to increase the surface area. Y3Pd2 will be selected as a model and the preparation process will be firstly tried by bottom-up method. Trialkylborohydride molten salt will be used as reducing reaction medium and the halide salts of Pd and Y as precursors. Under strong reducing environment, YCl3 could be reduced and afford nanoparticles (NPs). Moreover, the byproduct MCl (M = Na or K) would stabilize the newly formed Pd/Y NPs toward sintering and growth. On the other hand, we will also try the top-down method, the Pd-based intermetallic bulk samples will be firstly synthesized by arc-melting Y and Pd ingots. The obtained ingot will be tried by flash evaporation equipment or laser ablation apparatus respectively. After we got Pd-based intermetallic NPs, common C－C cross-coupling reactions will be also explored
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