2019 Fiscal Year Research-status Report
Development of manganese-catalyzed olefin metathesis reaction
| Project/Area Number |
18K14230
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
竹林 智司 沖縄科学技術大学院大学, サイエンステクノロジーグループ, 研究員 (10609283)
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| Project Period (FY) |
2018-04-01 – 2022-03-31
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| Keywords | メタロラジカル / コバルト / ヒドロフォルミル化 |
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| Outline of Annual Research Achievements |
I found that the manganese (Mn) olefin metathesis catalyst that reported last year's summary is rather difficult to formulate as the reaction appeared to be catalyzed by minor Mn impurities that formed during preparation of Mn complexes. The reaction is still catalyzed by Mn based on ESI-MS analysis of other metathesis active metal impurities such as Ru, however, we have not determined exactly which Mn impurity is catalyzing the reaction.
During the study of Mn N-hetero cyclic carbene (NHC) complexes I found that bulky NHC ligand can stabilize monomeric Mn(0) metalloradicals which usually exists as a dimer. Application of this strategy to an industrially important cobalt (Co) hydroformylation catalyst [Co(ligand)(CO)3]2 resulted in unprecedented isolation of [Co(NHC)(CO)3] metalloradicals. When less bulky NHC ligands were used [Co(NHC)(CO)3]2 dimers were obtained. Single crystal XRD analysis revealed that these dimers have the longest Co-Co bonds reported for [Co(ligand)(CO)3]2 complexes. The equilibrium between monomer and dimer was confirmed by EPR and NMR spectroscopies, and thermodynamic parameters for this equilibrium was determined. Isolation of the [Co(NHC)(CO)3] metalloradicals enabled us to investigate its reactivity towards H2 for the first time. Kinetic studies showed that this complex reacts with H2 by a bimolecular mechanism instead of the previously proposed termolecular mechanism. [Co(NHC)(CO)3]2 dimer reacted with H2 in dissociative mechanism and formed Co-hydride complex [HCo(NHC)(CO)3] under unusually mild conditions.
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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
Formulation of Mn impurity seems difficult. However, it is clear that manganese complexes can catalyze olefin metathesis reaction. We will put further effort to determine exact structure of the Mn complex that catalyzes the reaction. The planned elaboration of the Mn-catalyst will not be achieved during the planned period, however, unplanned isolation of cobalt metalloradical and discovery of it's unusual reactivity are more important discovery than elaboration of Mn-catalyst since it will open up new direction of catalysis.
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| Strategy for Future Research Activity |
For manganese project, we will put further effort to determine exact structure of the Mn complex that catalyzes the reaction, and publish the result.
For cobalt project, we will publish the discovery, and apply the discovered complexes for a new type of catalysis.
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| Causes of Carryover |
Until February 2020, I could not find an part-time research technician who I wanted to hire using KAKENHI. Now I have hired a part-time research technician who I pay ca. 80,000yen/month. This personnel cost will be ca 980,000 yen for this fiscal year.
In fiacal year 2019, I could not attend a conference in Tokyo due to COVID-19. I will attend 1-2 conferences in 2020-2021 if possible. This will cost 200,000-400,000 yen depend on conferences that I attend.
Finally, I am planning to purchase potentiostat or UV-VIS spectrometer (around 1,000,000 yen each) by combining KAKENHI and funding in OIST.
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