DFT Study of Acceptorless Alcohol Dehydrogenation Mediated by Ruthenium Pincer Complexes: Ligand Tautomerization Governing Metal Ligand Cooperation
DFT Study of Acceptorless Alcohol Dehydrogenation Mediated by Ruthenium Pincer Complexes: Ligand Tautomerization Governing Metal Ligand Cooperation
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钌钳配合物介导的无受体醇脱氢的 DFT 研究：配体互变异构控制金属配体合作
DOI：
10.1021/acs.inorgchem.6b00723
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发表时间：
2016-07-04
影响因子：
4.6
通讯作者：
Ke, Zhuofeng
中科院分区：
文献类型：
--
作者：
Hou, Cheng;Zhang, Zhihan;Ke, Zhuofeng
金属 - 配体协同作用（MLC）催化是设计高效过渡金属催化剂的一种常用策略。在本次理论研究中，我们以Szymczak的NNN - Ru和Milstein的PNN - Ru配合物作为两种代表性催化剂，描述了MLC机制中的关键控制因素。对外球和内球机制都进行了研究和比较。我们的计算结果表明，PNN - Ru钳形催化剂在催化循环过程中将恢复到芳香态，这可被视为推动MLC过程的驱动力。相反，对于NNN - Ru催化剂，MLC机制导致钳形配体发生不利的互变异构，这解释了MLC机制在该体系中失败的原因。因此，钳形配体所提供驱动力的强度实际上是MLC的一个先决条件。诸如CO、PPh₃和氢化物等旁观者配体对于确保催化剂遵循某种机制也很重要。我们还通过计算方法评估了各种双功能配体的驱动力。一些提出的钳形配体可能有潜力成为新的钳形催化剂候选物。本研究有望为MLC催化提供新的见解，并为未来的催化剂设计提供有用的指导。
Metal ligand cooperation (MLC) catalysis is a popular strategy to design highly efficient transition metal catalysts. In this presented theoretical study, we describe the key governing factor in the MLC mechanism, with the Szymczak's NNN-Ru and the Milstein's PNN-Ru complexes as two representative catalysts. Both the outer-sphere and inner-sphere mechanisms were investigated and compared. Our calculated result indicates that the PNN-Ru pincer catalyst will be restored to aromatic state during the catalytic cycle, which can be considered as the driving force to promote the MLC process. On the contrary, for the NNN-Ru catalyst, the MLC mechanism leads to an unfavored tautomerization in the pincer ligand, which explains the failure of the MLC mechanism in this system. Therefore, the strength of the driving force provided by the pincer ligand actually represents a prerequisite factor for MLC. Spectator ligands such as CO, PPh3, and hydride are important to ensure the catalyst follow a certain mechanism as well. We also evaluate the driving force of various bifunctional ligands by computational methods. Some proposed pincer ligands may have the potential to be the new pincer catalysts candidates. The presented study is expected to offer new insights for MLC catalysis and provide useful guideline for future catalyst design.