Intramolecular C-H activation in complexes with Mo-Bi metal bonds.
Intramolecular C-H activation in complexes with Mo-Bi metal bonds.
复制标题
具有 Mo-Bi 金属键的配合物中的分子内 C-H 活化。
DOI：
10.1002/anie.200353576
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发表时间：
2004
影响因子：
--
通讯作者：
M. Brandt
中科院分区：
文献类型：
--
作者：
S. Roggan;C. Limberg;B. Ziemer;M. Brandt
nMoO3/Bi2O3 相作为丙烯烯丙基氧化催化剂的独特性能仍然是激烈讨论的主题，这刺激了分子水平上元素组合 Mo/Bi 的研究。在含有这两种金属的已知化合物中，一类表现出直接的钼铋金属键，并且考虑到钼酸铋相的氧化特性，研究这种键在暴露于氧化剂时的行为似乎很有趣。然而，只有当残留络合物不受所用氧化剂的影响，并且直到最近所有已知的具有 Mo Bi 单元的化合物（例如 [ClBi{Mo(CO)3Cp}2] 和 [Mo2(CO)4( Cp)2(m-h -Bi2)] [4] (Cp=C5H5, Cp= C5H4Me) 以及某些其他化合物）时，这样的研究才有可能 在氧化条件下不呈惰性的配体。我们最近发现了一种合成路线，可产生具有氧化鲁棒配位层中的 Mo 和 Bi 中心且 Mo 中心处于相对较高氧化态的化合物：例如，用 [{Bi{OCH(CF3)2}3(thf)}2] 处理 [Cp2MoH2]，得到 [Cp2Mo(Bi{OCH(CF3)2}2)2] (1)，其功能 作为有效的环氧化预催化剂。在此，我们描述了对系统 [Cp2MoH2]/Bi(OtBu)3 的研究，该系统揭示了显着的 CH 激活过程。 [Cp2MoH2] 和 Bi(OtBu)3 以 1:2 的比例发生反应（方案 1），生成 [Cp2Mo{Bi(OtBu)2}2] (2)，用富电子叔丁基残基替换合成 1 时使用的缺电子六氟异丙基残基不会改变反应结果。 2 的分子结构如图 1 所示。虽然 3.487 9 的 Bi-Bi 间隔太长而无法用 Bi Bi 键来解释，但 75.278 的 Bi-Mo-Bi 角甚至小于 [Cp2MoH2] (75.58) [8] 中的 H-Mo-H 角，这意味着与 Mo 中心结合的两个 Bi(OR)2 部分之间不存在显着的排斥力。与
The unique property of nMoO3/Bi2O3 phases to act as catalysts for the allylic oxidation of propene remains a subject of intense discussion, that stimulates research with respect to the element combination Mo/Bi on the molecular level. Among the known compounds containing these two metals one class exhibits direct Mo Bi metal bonds, and, bearing in mind the oxygenating properties of bismuthmolybdate phases, it seems interesting to investigate the behavior of such linkages on exposure to oxidants. Such a study, however, is only possible, if the residual complex is not affected by the oxidizing-agent employed, and until recently all known compounds with Mo Bi units (e.g. [ClBi{Mo(CO)3Cp}2] and [Mo2(CO)4( Cp)2(m-h -Bi2)] [4] (Cp=C5H5, Cp= C5H4Me) as well as certain others ) contained ligands that are not inert under oxidizing conditions. We have recently found a synthetic route leading to compounds with both Mo and Bi centers in oxidatively robust coordination spheres and with the Mo centers in comparatively high oxidation states: For instance treatment of [Cp2MoH2] with [{Bi{OCH(CF3)2}3(thf)}2] provided [Cp2Mo(Bi{OCH(CF3)2}2)2] (1), which functions as an effective epoxidation precatalyst. Herein we describe the investigation of the system [Cp2MoH2]/Bi(OtBu)3 that revealed a remarkable C H activation process. The reaction between [Cp2MoH2] and Bi(OtBu)3 in a 1:2 ratio (Scheme 1) yields [Cp2Mo{Bi(OtBu)2}2] (2), the replacement of the electron-poor hexafluoroisopropyl residues employed in the synthesis of 1 by the electron-rich tertbutyl residues does not alter the outcome of the reaction. The molecular structure of 2 is depicted in Figure 1. While the Bi–Bi separation of 3.487 9 is too long to be interpreted in terms of a Bi Bi bond, the Bi-Mo-Bi angle of 75.278 is even smaller than the H-Mo-H angle in [Cp2MoH2] (75.58) [8] which means that there are no significant repulsive forces between the two Bi(OR)2 moieties bound to the Mo center. Unlike the