| 研究概要 |
We expect to develop a new synthetic route to the Schrock-type silylene and germylene complexes of the early transition metals. These novel coordination compounds are expected to be the efficient precursors for the [2 + 2] cycloadditions with unsaturated reagents in the silicon and germanium variations of the industrially very important metathesis process.
In the first year of the project, we synthesized the Schrock-type silylene and germylene complexes unprecedented in silicon and germanium chemistry. As the precursors for the preparation of these complexes, we used alkali and alkaline earth metal derivatives of the "heavy" cyclobutadiene [(R3Si)4E4](2-) 2[K(+)] and "heavy" bicyclo[1.1.0]butane [(R3Si)4E4](2-) [Ca(2+)] types (E = Si, Ge), very efficient in the synthesis of multiply bonded derivatives inaccessible in any other way. The reaction of these dianionic derivatives with the titanocene dichloride Cp2TiCl2 provided the the desired Schrock-type complexes, possessing Ti(L)=E double bond stabilized by the external Lewis basic ligand L.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
In the second year of the project, we investigate the [2 + 2] cycloaddition reactions of the newly synthesized Schrock-type titanium silylene and germylene complexes with a variety of unsaturated reagents, such as alkyl-, aryl-, silyl-substituted alkenes, alkynes, dienes and carbonyl compounds (formaldehyde, benzaldehyde, benzophenone, etc.). The reactions of such type, forming four-membered ring cycloaddition products, are still unprecedented in the silylene and germylene transition metal complexes chemistry.
Both titanium silylene and germylene complexes effectively react with a variety of the terminal alkynes (phenylacetylene, trimethylsilylacetylene, 1-hexyne, etc.) and nitriles (benzonitrile, pivalonitrile, etc.), regioselectively forming the corresponding [2+2] cycloadducts. The structures, physico-chemical properties and formation mechanism of these cycloadducts are studied by means of NMR spectroscopy, X-ray crystallography and high-level computations.
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| 今後の研究の推進方策 |
In the final third year of the project, we will expand the range of the group 4 metals to prepare also zirconium and hafnium silylene and germylene complexes. These complexes will be also tested for the use in the [2+2] cycloaddition reactions with the unsaturated substrates. Particular attention will be paid for the reaction of the complexes with ethylene and acetylene, because [2+2] cycloaddition products of these reactions are expected to undergo cycloreversion reactions. Such cycloreversion will provide a novel effective access to a variety of the multiply-bonded derivatives featuring double or triple bond to silicon or germanium atoms, as the key step toward the silicon or germanium versions of the olefin metathesis process.
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