Chiral Lanthanocene Derivatives Containing Two Linked Amido−Cyclopentadienyl Ligands: Heterobimetallic Structure and Lactone Polymerization Activity
Chiral Lanthanocene Derivatives Containing Two Linked Amido−Cyclopentadienyl Ligands: Heterobimetallic Structure and Lactone Polymerization Activity
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DOI：
10.1021/om9705867
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发表时间：
1997-10
期刊：
影响因子：
2.8
通讯作者：
K. Hultzsch;T. Spaniol;J. Okuda
中科院分区：
文献类型：
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作者：
K. Hultzsch;T. Spaniol;J. Okuda
2当量的氨基-环戊二烯基二锂Li 2（C5 R4 SiMe 2NCH 2CH 2X）（C5 R4 = C5 Me 4，C5 H3 tBu; X = OMe，NMe 2）与无水LnCl 3（Ln = Y，Lu）反应，得到含有杂双金属核的Li[Ln（η5：η1-C5 R4 SiMe 2NCH 2CH 2X）2]型C2对称配合物。Li[Y（η5：η1-C5 Me 4SiMe 2NCH 2CH 2 OMe）2]的晶体结构由单晶X射线衍射分析确定，结果表明它既具有准四面体的钇中心，又具有四面体的锂中心。根据在稀土金属中心Ln的正式20-电子配置，氨基氮原子被示出为结晶。在Li[Y（η5：η1-C5 H3 tBuSiMe 2NCH 2CH 2X）2]的情况下，形成取决于反应时间的相对比例的两种非对映异构体的混合物。（R，S）-非对映异构体是动力学产物，其在供体溶剂如THF中重排为在化学上优选的C2-对称（R，R）-非对映异构体。非对映体纯的（R，S）-Li[Y（η5：η1-C5 H3 tBuSiMe 2NC.
Reaction of 2 equiv of dilithium amido−cyclopentadienide Li2(C5R4SiMe2NCH2CH2X) (C5R4 = C5Me4, C5H3tBu; X = OMe, NMe2) with anhydrous LnCl3 (Ln = Y, Lu) gave C2-symmetric complexes of the type Li[Ln(η5:η1-C5R4SiMe2NCH2CH2X)2] containing a heterobimetallic core. The molecular structure of Li[Y(η5:η1-C5Me4SiMe2NCH2CH2OMe)2] was determined by single-crystal X-ray structural analysis, which showed it to exhibit both a pseudotetrahedral yttrium as well as a tetrahedral lithium center. In accordance with a formal 20-electron configuration at the rare earth metal center Ln, the amido-nitrogen atoms are shown to be pyramidalized. In the case of Li[Y(η5:η1-C5H3tBuSiMe2NCH2CH2X)2], mixtures of the two diastereomers in relative ratios depending on the reaction time are formed. The (R,S)-diastereomer is the kinetic product that rearranges to the thermodynamically preferred C2-symmetric (R,R)-diastereomer in donor solvents such as THF. The molecular structures of diastereomerically pure (R,S)-Li[Y(η5:η1-C5H3tBuSiMe2NC...