Hydroboration of Bis(alkenylcyclopentadienyl)zirconium Dichlorides
Hydroboration of Bis(alkenylcyclopentadienyl)zirconium Dichlorides
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双(烯基环戊二烯基)二氯化锆的硼氢化反应
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
R. Aul
中科院分区：
文献类型：
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作者：
G. Erker;R. Aul
烯丙基环戊二烯基锂与0.5摩尔当量的MCl 4（thf）2（MZr，Hf）反应得到（η5-C5 H4 CH 2CHCH 2 MCl 2）配合物3a（Zr）和3b（Hf），其干净地加入9-硼双环[3.3.1]壬烷（9-BBN）以形成[η5-C5 H4（CH 2）3（9-BBN）] 2 MCl 2（10a，B）。用丁二烯-镁处理3导致一个Cp键合的烯丙基单元与丁二烯偶联，得到5;当暴露于9-BBN硼氢化试剂时，剩余的CpCH 2CHCH 2基团经历干净的H[B（C8 H 14）]加成。（烯基-Cp）2 ZrCl 2配合物（9a-d）由富烯开始通过在LDA的帮助下脱质子化并与ZrCl 4（thf）2反应来制备。配合物[η_5-C_5H_4CHC（CH_3）R]_2ZrCl_（29）b（RCH_3）和9 c（RPh）与9-BBN反应，得到[η_2-C_5H_4CH（9-BBN）CH（CH_3）R]_2ZrCl_（212）（RCH_3，外消旋;-/内消旋;-内消旋1：1）和13（RPh，苏型;-/内消旋;-内消旋1：1）。在每种情况下，通过分级结晶分离非对映异构体的混合物。配合物rac;-12和meso;-12的立体化学归属通过在12/甲基铝氧烷衍生的均相齐格勒型烯烃聚合催化剂上形成的聚丙烯的立体化学实现。在-50 °C下，来自非手性meso;-12前体的催化剂仅通过“链端控制”（σ = 0.7）产生全同立构聚丙烯，而使用外消旋;-12导致CC偶联反应中有效的“对映异构体位点控制”（α=0.95）的显著参与（约30%）。
The reaction of allylcyclopentadienyllithium with 0.5 molar equivalents of MCl4(thf)2 (MZr, Hf) furnished the (η5-C5H4CH2CHCH2MCl2 complexes 3a (Zr) and 3b (Hf), which cleanly added 9-borabicyclo[3.3.1]nonane (9-BBN) to form [η5-C5H4(CH2)3(9-BBN)]2MCl2 (10a, b). Treatment of 3 with butadiene-magnesium led to coupling of one Cp-bonded allyl unit with butadiene to give 5; the remaining CpCH2CHCH2 group underwent clean H[B(C8H14)] addition when exposed to the 9-BBN hydroboration reagent. (Alkenyl-Cp)2ZrCl2 complexes (9a – d) were prepared starting from fulvenes by deprotonation with the help of LDA and reaction with ZrCl4(thf)2. The complexes [η5-C5H4CHC(CH3)R]2ZrCl29b (RCH3) and 9c (RPh) added 9-BBN to give [η2-C5H4CH(9-BBN)CH(CH3)R]2ZrCl212 (RCH3, rac;-/meso;- ≈ 1:1) and 13 (RPh, threo;-/erythro;- ≈ 1:1). The mixtures of diastereoisomers were in each case separated by fractional crystallization. The stereochemical assignments of complexes rac;-12 and meso;-12 were achieved by means of the stereochemistry of polypropylene formed at the 12/methylalumoxane-derived homogeneous Ziegler-type olefin polymerization catalysts. At – 50°C the catalyst from the achiral meso;-12 precursor produced isotactic polypropylene only by means of “chain end control” (σ ≈ 0.7), whereas the use of rac;-12 led to a pronounced participation (≈ 30%) of effective “enantiomorphic site control” (α=0.95) in the CC-coupling reaction.