Synthesis of a Chiral Meso-Like Ansa-Zirconocene Complex and its Use for the Catalytic Formation of Low Molecular Weight Polypropylene
Synthesis of a Chiral Meso-Like Ansa-Zirconocene Complex and its Use for the Catalytic Formation of Low Molecular Weight Polypropylene
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手性内消旋型柄型二茂锆配合物的合成及其在催化形成低分子量聚丙烯中的应用
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发表时间：
1995
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通讯作者：
R. Fröhlich
中科院分区：
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作者：
S. Thiele;G. Erker;C. Fritze;C. Psiorz;R. Fröhlich
锂（新薄荷基环戊二烯基）3与二甲基二氯硅烷反应，区域选择性地得到二甲基双[3-（新薄荷基）正]硅烷4，其为双键移位异构体的混合物（57%分离）。用2当量去质子化。用四氯化锆处理后得到三种{二甲基亚硅基双[η5-3-（新薄荷基）双][二氯化锆非对映体]的混合物，通过分级结晶从其中分离出纯的内消旋异构体6 e [p-R（1′ S，3 ′R，4 ′R），p-S（1′S，3 ′R，4 ′R）]。通过X-射线晶体结构分析对配合物6c进行了表征。它的D1-Zr-D2角为126.8°，与双（η-ZrO 2）二氯化锆（D1和D2表示双（η-ZrO 2）二氯化锆的质心）非常相似。均相6c/甲基铝氧烷齐格勒型催化剂生产低分子量聚丙烯（在环境温度下Mη = 670）。相关的催化剂体系可能在有机合成中找到令人感兴趣的应用。
Reaction of lithium(neomenthylcyclopentadienid) 3 with dimethyldichlorosilane gives dimethylbis[3-(neomenthyl)cyclopentadienyl]silane 4 regioselectively as a mixture of double bond shift isomers (57% isolated). Deprotonation with 2 equiv. of butyllithium followed by treatment with zirconiumtetrachloride furnished a mixture of the three {dimethylsilylenbis[η5-3-(neomenthyl)cyclopentadienyl][zirconium dichloride diastereomers from which the pure meso-like isomer 6e [p -R (1′S ,3 ′R ,4 ′R),p -S (1′S ,3 ′R ,4 ′R)] was isolated by fractional crystallization. Complex 6 c was characterized by an X-ray crystal structure analysis. Its D 1 - Zr - D 2 angle of 126.8° is very similar as observed in bis(η-cyclopentadienyl) zirconium dichloride (D 1 and D 2 denote the centroids of the cyclopentadienyl rings). The homogeneous 6c/methylalumoxane Ziegler-type catalyst produces polypropylene of low molecular weight (Mη ≈ 670 at ambient temperature). Related catalyst systems may find interesting applications in organic synthesis.