2014 Fiscal Year Research-status Report
Selective Isomerization and Transformation of Aromatic Hydrocarbons by Using Polynuclear Transition Metal Hydride Complexes
| Project/Area Number |
26810041
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| Research Institution | The Institute of Physical and Chemical Research |
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Principal Investigator |
HU SHAOWEI 独立行政法人理化学研究所, 環境資源科学研究センター, 特別研究員 (30713036)
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| Project Period (FY) |
2014-04-01 – 2016-03-31
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| Keywords | C-C bond cleavage / benzene / titanium polyhydride |
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| Outline of Annual Research Achievements |
Aromatic compounds are widely found in natural resources such as petroleum and biomass, and breaking them into smaller hydrocarbon fragments plays an important role in the production of fuels and valuable chemicals. However, carbon-carbon bonds of aromatic compounds are very stable and difficult to break under ordinary conditions. We found the C-C bond cleavage and rearrangement of benzene by a trinuclear titanium polyhydride complex. A benzene ring can be transformed sequentially to methylcyclopentenyl and 2-methylpentenyl species through hydrogenating and breaking the aromatic carbon skeleton at the multi-titanium sites. It is the first example of carbon-carbon bond cleavage and rearrangement of benzene by a well-defined molecular system. These findings demonstrate that multinuclear titanium hydrides can serve as a unique platform for the activation of aromatic molecules, and may help design and construct new catalysts for more efficient and selective production of useful materials from natural resources.So far, part of this research result has been published on Nature in 2014.
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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
So far we have investigated the fundamental aspects of this C-C bond cleavage and skeletal rearrangement reactions of benzene promoted by trinuclear titanium heptahydride complex. We have explored and characterized all the reaction products and isolated the key intermediate in the transformation. This results has been published in Nature. Besides, we are now cooperating with some specialist in computation area to clarify the detailed mechanisms of this cleavage and transformation of the extremely inert aromatic rings. Currently the collection of the data has been completed and manuscript is under preparation.
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| Strategy for Future Research Activity |
In the future, we will focus our research in the liberation of the activated carbon unit and make catalytic cycle for the transformation of aromatic hydrocarbons to isomerized compounds.
a.through hydrogenolysis reactions.
b.through reaction with hydride reagent (for organic synthesis).
Further elaboration of the catalytic reaction mechanisms will be conducted (through monitoring the reactions and isolating the key intermediates) as well.
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| Causes of Carryover |
Last fiscal year we have investigated the stoichiometric reactions of aromatic molecule activation including the structure characterization and processes analysis. However, the conferences expense and the reagents cost are not as much as we expected at early time, and at same time we have't bought some apparatus because the research progress is not as scheduled. So we apply to move the rest of the kakenhi to the next year. For the further research, we will explore the catalytic reactions to liberate the activated carbon fragment through using H2 or some simple hydride reagents. These studies definitely need more input, no matter for reagents, glasswares or high pressure apparatus.
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| Expenditure Plan for Carryover Budget |
Catalytic transformation of aromatic hydrocarbons to isomerized cycloalkanes or branched alkanes will be developed.
Based on the results in last fiscal year, attempts to achieve catalytic transformation of aromatic hydrocarbons to isomerized compounds will be conducted. The carbon skeletal from benzene activation by titanium hydride complex will be liberated to afford methylcyclopentane or iso-hexane (or substituted methylcyclopentane) through hydrogenolysis (or addition of simple hydride reagent) under mild conditions. Other aromatic substrates will also be checked,such as toluene, xylene and naphthalene.The reaction mechanism will be elucidated through NMR monitoring and isolating key intermediates.
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