2016 Fiscal Year Annual Research Report
異種二核金属錯体と第二配位圏の遷移金属錯体による酸化触媒及びＣＨ活性化触媒の創出
| Project/Area Number |
16F16038
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
クスヌディノワ ジュリア 沖縄科学技術大学院大学, 錯体化学・触媒ユニット, 准教授 (90747544)
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| Co-Investigator(Kenkyū-buntansha) |
RIVADA WHEELAGHAN ORESTES 沖縄科学技術大学院大学, 錯体化学・触媒ユニット, 外国人特別研究員
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| Project Period (FY) |
2016-07-27 – 2019-03-31
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| Keywords | polynuclear complexes / heterobimetallic complex / copper complexes / ligand design / aerobic oxidation / homogeneous catalysis |
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| Outline of Annual Research Achievements |
We have completed all of the steps of the proposed plan for FY2017. First, we have synthesized several polynucleating ligands bearing naphthyridinone backbone and characterized the ligands by spectroscopic methods.
Then, we have synthesized several types of polynuclear complexes including: binuclear mixed Pt-Cu complexes; two types of tetranuclear Cu-Pd-Pd-Cu complexes; tetranuclear Cu-Cu-Cu-Cu (Cu4) and a trinuclear Cu-Cu-Cu (Cu3) linear chain complexes. These complexes were characterized by spectroscopic methods and/or by X-ray diffraction. We have shown for the first time that controlled and selective formation of linear chain Cu4 and Cu3 complexes can be achieved by modifying auxiliary ligand fragment. By changing number of N-donor atoms in the ligand, we achieved formation of only Cu3 or only Cu4 complexes in a selective fashion. This result sheds light on possible ways of controlling nuclearity of linear chain complexes.
Finally, we have found that Cu4 complexes are catalytically active in oxidation of benzyl amines to imines using 1 bar of O2 or air under mild conditions (5 mol%, THF or DMF, 60 degrees C). The unusual feature of this reaction is that no nitroxyl radical additives are necessary to obtain good yield. This is uncommon in the literature to observe selective copper-catalyzed amine oxidation in the absence on nitroxyl radicals. Moreover, alcohols could be oxidized to aldehydes, albeit with low yields. Nitroxyl-free oxidation can open pathways for more economical ways to utilized Cu complexes on selective oxidation that avoids expensive nitroxyl additives.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Generally, all proposed steps of plan for FY2016 were completed, such as ligand synthesis, complex synthesis, and initial catalytic screening studies. Mechanistic studies will be performed in the following year to complete the first project on copper complexes and their catalytic activity.
New findings include nitroxyl-free aerobic amine oxidation catalyzed by copper-only polynuclear complexes.
In view of our findings of the copper-catalyzed aerobic reactivity, the initial focus shifted more towards studying tetra- and trinuclear copper-only complexes. In January 2017, synthetically challenging mixed Cu-Pd-Pd-Cu linear chain organometallic complexes were obtained and they will be studied in FY2017.
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| Strategy for Future Research Activity |
In the future, we plan to complete first project related to studying polynuclear copper complexes in aerobic oxidation of amines and alcohols. Reaction conditions will be optimized to obtained higher yields and selectivities. We will attempt to control selectivity of amine oxidation and obtain nitriles as an alternative product. We will study mechanism of aerobic oxidation by low temperature UV-vis and ESR spectroscopy.
Furthermore, we will study heterobimetallic Cu-Pd-Pd-Cu complexes in aerobic C-H bond activation catalysis. Due to presence of both Pd and Cu centers, it is expected that enhanced reactivity on aerobic C-H bond oxidation will be obtained, where Pd center will participate in C-H bond activation, and Cu center is know to easily activate O2.
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