Chiral Cationic [Cp′Mo(CO)2(NCMe)]+ Species – Catalyst Precursors for Olefin Epoxidation with H2O2 and tert‐Butyl Hydroperoxide
Chiral Cationic [Cp′Mo(CO)2(NCMe)]+ Species – Catalyst Precursors for Olefin Epoxidation with H2O2 and tert‐Butyl Hydroperoxide
复制标题
手性阳离子 [Cp′Mo(CO)2(NCMe)]+ 物质 - H2O2 和叔丁基过氧化氢烯烃环氧化反应的催化剂前体
DOI：
--
复制
发表时间：
2011
期刊：
影响因子：
--
通讯作者：
B. Royo
中科院分区：
文献类型：
--
作者：
P. Reis;C. Gamelas;José A. Brito;Nathalie Saffon;M. Gómez;B. Royo
合成了一种新型的含手性恶唑啉侧基的手性配体（Cpox）.其与钼和钨的配位得到光学纯的（R）-CpoxM（η3-C3 H5）（CO）2（M = Mo，W），其中侧链恶唑啉片段不与金属中心配位。（R）-CpoxMo（η3-C3 H5）（CO）2与四氟硼酸反应，得到双齿η5-环戊二烯基恶唑啉配合物[CpoxMo（CO）2（NCMe）] BF 4，其中恶唑啉通过N原子与钼中心配位。研究了它们在H_2O_2和叔丁基过氧化氢（TBHP）氧化顺式环辛烯、（R）-柠檬烯和反式-β-甲基苯乙烯环氧化反应中的催化性能。（R）-CpoxW（η3-C3 H5）（CO）2表现出高的催化活性，在2 h内用H2 O2实现了环氧化物环辛烯的定量转化。[CpoxMo（CO）2（NCMe）]+与TBHP和H2 O2一起被证明是有效的催化剂，分别在30 min和11 h内达到相应环氧化物的定量转化。[CpoxMo（CO）2（NCMe）]+与H_2O_2和TBHP反应的ESI-MS研究分别揭示了相应的过氧化物[CpoxMo（O_2）O]+和二氧化物[CpoxMoO_2]+物种的原位形成。这些配合物的进一步氧化导致环戊二烯基恶唑啉配体的损失。基于自旋捕获实验，证明了[CpoxMo（CO）2（NCMe）]+催化烯烃环氧化反应中碳中心自由基和氧中心自由基的参与.
A novel cyclopentadienyl ligand bearing a chiral oxazoline pendant group (Cpox) has been prepared. Its coordination to molybdenum and tungsten afforded optically pure (R)-CpoxM(η3-C3H5)(CO)2 (M = Mo, W) in which the pendant oxazoline fragment is not coordinated to the metal center. Reaction of (R)-CpoxMo(η3-C3H5)(CO)2 with tetrafluoroboric acid gives the bidentate η5-cyclopentadienyloxazoline complex [CpoxMo(CO)2(NCMe)]BF4 in which the oxazoline is coordinated through the N-atom to the molybdenum center. Their catalytic performance in the epoxidation of cis-cyclooctene, (R)-limonene, and trans-β-methylstyrene with H2O2 and tert-butyl hydroperoxide (TBHP) as oxidants has been studied. (R)-CpoxW(η3-C3H5)(CO)2 displayed high catalytic activity achieving quantitative conversion of cyclooctene epoxide in 2 h with H2O2. [CpoxMo(CO)2(NCMe)]+ has been shown to be an efficient catalyst with TBHP and H2O2, reaching quantitative conversions of the corresponding epoxide in 30 min and 11 h, respectively. ESI-MS studies of the reaction of [CpoxMo(CO)2(NCMe)]+ with H2O2 and TBHP revealed the in situ formation of the corresponding peroxido [CpoxMo(O2)O]+ and dioxido [CpoxMoO2]+ species, respectively. Further oxidation of these complexes resulted in the loss of the cyclopentadienyloxazoline ligand. Based on spin trap experiments, the involvement of both carbon- and oxygen-centred radicals in the olefin epoxidation catalyzed by [CpoxMo(CO)2(NCMe)]+ has been proved.