Remarkable stability of metallocenes with superbulky ligands: spontaneous reduction of Sm(III) to Sm(II).
Remarkable stability of metallocenes with superbulky ligands: spontaneous reduction of Sm(III) to Sm(II).
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DOI：
10.1002/anie.200705001
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发表时间：
2008-02
影响因子：
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通讯作者：
Christian Ruspic;J. R. Moss;M. Schürmann;S. Harder
中科院分区：
文献类型：
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作者：
Christian Ruspic;J. R. Moss;M. Schürmann;S. Harder
含有极其庞大的配体（例如全苯基化环戊二烯基配体（Ph5C5））的配合物已显示出独特的性质或配位几何形状。 [1]例如，卡宾类似物十甲基锡茂 ([Cp* 2SnII], Cp*= C5Me5) 的典型弯曲结构可以通过使用 Ph5C5 配体进行线性化。 [2]令人惊讶的是，通过 Ph5C5C 自由基与 Ni0 衍生物反应制备的二茂镍络合物 [(Ph5C5) 2Ni] 具有抗磁性。 [3] [(Ph5C5)2Fe]的存在因其环距较短而长期存在争议。[4]如今，已知有两种连接异构体：空间松弛的两性离子 η5, η6-复合物 1 [5] 和空间拥挤的 (η5, η5)-茂金属 2。[6]有关在催化中使用 Ph5C5 配体的首次报道表明，它极大地增强了不对称合成中的立体选择性。[7]此外，大量配体增加了铬催化乙烯低聚反应的活性和选择性。 [8]由于碱土金属和镧系金属的半夹心配合物是具有广泛应用的有效且有前途的催化剂，[9]我们致力于在这些化合物类别中引入超大环戊二烯基配体。我们令人惊讶的初步结果表明，相反
Complexes containing extremely bulky ligands such as the perphenylated cyclopentadienyl ligand (Ph5C5) have shown unique properties or coordination geometries.[1] For example, the typical bent structures of the carbene analogue decamethylstannocene ([Cp* 2SnII], Cp*= C5Me5) can be linearized by use of Ph5C5 ligands.[2] Surprisingly, the nickelocene complex [(Ph5C5) 2Ni], prepared by reaction of the Ph5C5C radical with a Ni0 derivative, is diamagnetic.[3] The existence of [(Ph5C5) 2Fe] was long disputed on the basis of its short ring–ring distance.[4] Today, two linkage isomers are known: the more sterically relaxed zwitterionic η5, η6-complex 1 [5] and the sterically congested (η5, η5)-metallocene 2.[6]First reports on the use of the Ph5C5 ligand in catalysis show that it greatly enhances stereoselectivity in asymmetric syntheses.[7] Moreover, the bulk of the ligand increases the activity and selectivity in chromium-catalyzed ethylene oligomerization.[8] As half-sandwich complexes of alkaline-earth and lanthanide metals are effective and promising catalysts for a wide variety of applications,[9] we pursued the introduction of superbulky cyclopentadienyl ligands in these compound classes. Our surprising initial results show that instead