Why Two Metals Are Better Than One for Heterodinuclear Cobalt–Zirconium-Catalyzed Kumada Coupling
Why Two Metals Are Better Than One for Heterodinuclear Cobalt–Zirconium-Catalyzed Kumada Coupling
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DOI：
10.1021/acs.organomet.8b00449
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发表时间：
2018-11
期刊：
影响因子：
2.8
通讯作者：
James C. Coombs;Dalton Perry;Doo-Hyun Kwon;Christine M. Thomas;D. Ess
中科院分区：
文献类型：
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作者：
James C. Coombs;Dalton Perry;Doo-Hyun Kwon;Christine M. Thomas;D. Ess
与单核催化剂相比，具有直接金属-金属相互作用的异双核过渡金属配合物具有独特的反应活性。磷酰胺配体桥接Co和Zr金属中心的杂双核Co - Zr配合物是烷基卤化物与烷基卟啉之间Kumada C-C键偶联反应的有效预催化剂。相反，不含Zr的类似的单核Co - tris（phosphinoamine）配合物的催化效率非常低。本文描述了密度泛函理论计算，揭示了Co-Zr金属-金属相互作用和磷脂酰胺配体对烷基卤化物-烷基Grignard - Kumada偶联催化的机理和反应性影响。Co-Zr相互作用使预催化剂的双电子还原形成活性催化剂，从而促进低能电子转移烷基卤化物氧化加成机制。Co-Zr相互作用和桥接金属中心的磷脂酰胺配体提供了具有…
Heterodinuclear transition metal complexes with a direct metal–metal interaction offer the potential of unique reactivity compared with mononuclear catalysts. Heterodinuclear Co–Zr complexes with phosphinoamide ligands bridging Co and Zr metal centers are effective precatalysts for Kumada C–C bond coupling reactions between alkyl halides and alkyl Grignards. In contrast, the analogous mononuclear Co tris(phosphinoamine) complex without Zr provides very inefficient catalysis. Here we describe density functional theory calculations that reveal the mechanistic and reactivity impact of the Co–Zr metal–metal interaction and phosphinoamide ligands on alkyl halide–alkyl Grignard Kumada coupling catalysis. The Co–Zr interaction enables two-electron reduction of the precatalyst to form an active catalyst, which then promotes a low-energy electron-transfer alkyl halide oxidative addition mechanism. The Co–Zr interaction and the phosphinoamide ligands bridging the metal centers provide a dialkyl intermediate with a ...