Spin-Blocking Effect in CO and H2 Binding Reactions to Molybdenocene and Tungstenocene: A Theoretical Study on the Reaction Mechanism via the Minimum Energy Intersystem Crossing Point

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• 作者：K-jiro Watanabe ; Naoki Nakatani ; Akira Nakayama ; Masahiro Higashi ; Jun-ya Hasegawa
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：August 15, 2016
• 年：2016
• 卷：55
• 期：16
• 页码：8082-8090
• 全文大小：559K
• 年卷期：0
• ISSN：1520-510X

文摘

Potential energy profiles and electronic structural interpretation of the CO and H₂ binding reactions to molybdenocene and tungstenocene complexes [MCp₂] (M = Mo and W, Cp = cycropentadienyl) were studied using density functional theory calculations and ab initio multiconfigurational electronic structure calculations. Experimentally observed slow H₂ binding was reasonably explained in terms of the spin-blocking effect. Electronic structural analysis at the minimum-energy intersystem crossing point (MEISCP) revealed that the singly occupied molecular orbital’s π-bonding/σ-antibonding character in the M-CO/H₂ moiety determines the energy levels of the MEISCP. Analysis of the reaction coordinate showed that the singlet-triplet gap significantly depends on the Cp-M-Cp angle. Therefore, not only the metal–ligand distance but also the Cp-M-Cp angle is an important reaction coordinate to reach the MEISCP, the transition state of H₂ binding. The role of spin–orbit coupling is also discussed.