Reductive Cleavage of CO2 by Metal-Ligand-Cooperation Mediated by an Iridium Pincer Complex
Reductive Cleavage of CO2 by Metal-Ligand-Cooperation Mediated by an Iridium Pincer Complex
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DOI：
10.1021/jacs.6b00202
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发表时间：
2016-05-25
影响因子：
15
通讯作者：
Milstein, David
中科院分区：
文献类型：
--
作者：
Feller, Moran;Gellrich, Urs;Milstein, David
描述了一种基于金属配体合作的化学计量的CO活化和还原裂解的独特模式。新型Ir氢化物配合物[（Bu-t-PNP*）Ir（H）（2）]（2）（Bu-t-PNP*，去质子化的Bu-t-PNP配体）和[（Bu-t-PNP）Ir（H）]（3）与CO反应，得到脱芳构化的配合物[（Bu-t-PNP*）Ir（CO）]（4）和水。机理研究已经确定了其中CO2与配体和金属结合的加合物[（Bu-t-PNP-COO）Ir（H）（2）]（5）和二-CO2铱配体[（Bu-t-PNP）Ir（H）（C2 O 4-kappa（C，O））]（6）。DFT计算证实了5和6作为可逆形成的副产物的形成，并提出了导致热力学产物4的eta（1）-CO2中间体。计算结果支持金属配体合作途径，其中由eta（1）-CO2配体的苄基位置的内部去质子化导致羧酸酯中间体，其进一步与氢化物配体反应，得到配合物4和水。
A unique mode of stoichiometric CO, activation and reductive splitting based on metal ligand-cooperation is described. The novel Ir hydride complexes [(Bu-t-PNP*)Ir(H)(2)] (2) (Bu-t-PNP*, deprotonated Bu-t-PNP ligand) and [(Bu-t-PNP)Ir(H)] (3) react with CO, to give the dearomatized complex [(Bu-t-PNP*)Ir(CO)] (4) and water. Mechanistic studies have identified an adduct in which CO2 is bound to the ligand and metal, [(Bu-t-PNP-COO)Ir(H)(2)] (5), and a di-CO2 iridacycle [(Bu-t-PNP)Ir(H)(C2O4-kappa(C,O))] (6). DFT calculations confirm the formation of 5 and 6 as reversibly formed side products, and suggest an eta(1)-CO2 intermediate leading to the thermodynamic product 4. The calculations support a metal ligand-cooperation pathway in which an internal deprotonation of the benzylic position by the eta(1)-CO2 ligand leads to a carboxylate intermediate, which further reacts with the hydride ligand to give complex 4 and water.