Coordinative Unsaturation in Chiral Organolanthanides. Synthetic and Asymmetric Catalytic Mechanistic Study of Organoyttrium and -lutetium Complexes Having Pseudo-meso Me2Si(η5-RC5H3)(η5-R*C5H3) Ancillary Ligation1
Coordinative Unsaturation in Chiral Organolanthanides. Synthetic and Asymmetric Catalytic Mechanistic Study of Organoyttrium and -lutetium Complexes Having Pseudo-meso Me2Si(η5-RC5H3)(η5-R*C5H3) Ancillary Ligation1
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DOI：
10.1021/om950871v
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发表时间：
1996-04
期刊：
影响因子：
2.8
通讯作者：
Christopher M. Haar;C. Stern;T. Marks
中科院分区：
文献类型：
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作者：
Christopher M. Haar;C. Stern;T. Marks
通过NMR、圆二色谱和X射线衍射证实，新螯合配体Me 2Si（3-Me 3SiCp）[3-（−）-menthylCp]2-（Cp = η5-C5 H3）的有机镧系元素配合物优先采用不对称金属−配体模板的单一平面手性构型。氯配合物（S，R）-Me 2Si（Me 3SiCp）[（-）-薄荷基Cp]Ln（μ-Cl）2Li（OEt 2）2（Ln = Y，Lu）通过从乙醚中结晶分离出非对映体纯的。不寻常的伪介观构型导致了理想C2 v对称性的严重扭曲，这可以从Sibridge−Lu−Li与线性（158°）的显著偏差中得到证明。在THF溶液中检测到至少两种额外的差向异构体。用巫妖（SiMe 3）2进行（S，R）差向异构体的烷基化，保留构型，以定量产率提供手性烃基络合物。在溶液中，在NMR中，由于Ln-CH（SiMe 3）2键的限制旋转，这些取代基表现出依赖于温度的构象交换过程。这些化合物是有效的预...
As established by NMR, circular dichroism, and X-ray diffraction, organolanthanide complexes of the new chelating ligand Me2Si(3-Me3SiCp)[3-(−)-menthylCp]2- (Cp = η5-C5H3) preferentially adopt a single planar chiral configuration of the asymmetric metal−ligand template. Chloro complexes (S,R)-Me2Si(Me3SiCp)[(−)-menthylCp]Ln(μ-Cl)2Li(OEt2)2 (Ln = Y, Lu) were isolated diastereomerically pure by crystallization from diethyl ether. The unusual pseudo-meso configuration leads to a gross distortion from ideal C2v symmetry, evidenced by a significant deviation of ∠Sibridge−Lu−Li from linearity (158°). At least two additional epimers are detected in THF solution. Alkylation of the (S,R) epimers with LiCH(SiMe3)2 proceeds with retention of configuration, affording chiral hydrocarbyl complexes in quantitative yield. In solution, the hydrocarbyls exhibit temperature-dependent conformational exchange processes in the NMR ascribable to restricted rotation about the Ln−CH(SiMe3)2 bond. These complexes are effective pre...