Impact of Ligands and Metals on the Formation of Metallacyclic Intermediates and a Nontraditional Mechanism for Group VI Alkyne Metathesis Catalysts.
Impact of Ligands and Metals on the Formation of Metallacyclic Intermediates and a Nontraditional Mechanism for Group VI Alkyne Metathesis Catalysts.
复制标题
配体和金属对金属环中间体形成的影响和VI族炔复分解催化剂的非传统机理。
DOI：
10.1021/jacs.1c01843
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发表时间：
2021-06-23
影响因子：
15
通讯作者：
Lee S
中科院分区：
文献类型：
--
作者：
Thompson RR;Rotella ME;Zhou X;Fronczek FR;Gutierrez O;Lee S
作为基于[2 + 2]/逆-[2 + 2]环加成的机制的一部分的金属环丁二烯的中间体是炔复分解中的一个完善的范例，其中替代物质被视为干扰有效产物形成的非循环分解产物。最近的工作表明，从硅氧化物豆荚负载的钼基催化剂中分离出的唯一中间体不是预期的金属环丁二烯，而是动态金属四面体。尽管它们在化学文献中很少，但理论工作表明这些物种在化学上更稳定，并且具有适度的环加成障碍。因此，我们报告的第VI组alkylidyne库的合成以及角色金属身份，配体的灵活性，二级配位领域，和基板身份都有上isolable中间体。此外，我们报告的差异，催化剂的能力作为配体空间位阻和金属选择的函数。色散校正的DFT计算用于阐明的机制和作用的配体和金属的金属环丁二烯和金属四面体的中间体，以及它们的影响，炔复分解。
The intermediacy of metallacyclobutadienes as part of a [2 + 2]/retro-[2 + 2] cycloaddition-based mechanism is a well-established paradigm in alkyne metathesis with alternative species viewed as off-cycle decomposition products that interfere with efficient product formation. Recent work has shown that the exclusive intermediate isolated from a siloxide podand-supported molybdenum-based catalyst was not the expected metallacyclobutadiene but instead a dynamic metallatetrahedrane. Despite their paucity in the chemical literature, theoretical work has shown these species to be thermodynamically more stable as well as having modest barriers for cycloaddition. Consequentially, we report the synthesis of a library of group VI alkylidynes as well as the roles metal identity, ligand flexibility, secondary coordination sphere, and substrate identity all have on isolable intermediates. Furthermore, we report the disparities in catalyst competency as a function of ligand sterics and metal choice. Dispersion-corrected DFT calculations are used to shed light on the mechanism and role of ligand and metal on the intermediacy of metallacyclobutadiene and metallatetrahedrane as well as their implications to alkyne metathesis.
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