| Budget Amount *help |
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2004: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2003: ¥4,200,000 (Direct Cost: ¥4,200,000)
Fiscal Year 2002: ¥9,200,000 (Direct Cost: ¥9,200,000)
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| Research Abstract |
1,2-Bis[2-(bis(2-pyridylmethyl)aminomethyl)-6-pyridyl]ethane (6-HPA) was prepared as a new dinucleating ligand, where two tris(2-pyridylmethyl)amine (TPA) units are attached to a -CH_2CH_2- tether at the 6-py position. 6-HPA forms the diiron(III) complex [Fe_2(6-HPA)(O)(OH_2)_2](ClO_4)_4 (1), which acts as functional models of sMMO. Crystal structure of 1 was determined by X-ray analysis. Given the stable diiron core, 1 catalyzes the predominant epoxidation of the alkene with H_2O_2, where both a high yield and large turnover number were attained; trans-β-methylstyrene gave the trans-epoxide in 91% yield and the turnover number exceeded one hundred. A high epoxide yield for the alkene with low ionization potential and trans-epoxide production from cis-β-methylstyrene indicated that a one-electron oxidation of the alkene had occurred. The radical cation given was partly rearranged from cis to trans. The addition of 2 eq of H_2O_2 to 1 at -40℃ in MeCN generated a green species 4. The electronic absorption data, 490 nm (1130 M^<-1> cm^<-1>), 670 (1060), and 882 (sh, 370), with the main peak of the CSI MS at m/z 865, and a shift to m/z 869 with H_2^<18>O_2 shows that 4 is a μ-oxo-μ-peroxodiiron(III). ^<18>O-labeling experiments using trans-β-methylstyrene as a substrate were carried out under various conditions using H2^<18>O_2, μ-^<18>O-1, H_2^<18>O, and ^<18>O_2 to gain some insights into the O_2-activation mechanism. ^<18>O was incorporated into 94% of the epoxide with H_2^<18>O_2/1 (10/1, mol/mol) under Ar and into 31 or 17% of the epoxide with H_2^<16>O_2/μ-^<18>O-1 (1/1) or (3/1) under Ar. The data clearly showed that O-atoms of μ-O and μ-O_2 in 4 were incorporated equivalently into the epoxide. 4 may be converted to a dioxo-μ-oxodiiron(IV) via homolytic scission of the O-O bond, where three O-atoms scramble one another.
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