Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany.
Chemistry. 2023 Jan 2;29(1):e202202602. doi: 10.1002/chem.202202602. Epub 2022 Nov 14.
Recently, it was shown that the double Ca-H-Ca bridged calcium hydride cation dimer complex [LCaH CaL] (macrocyclic ligand L=NNNN-tetradentate Me TACD) exhibited remarkable activity in catalyzing the hydrogenation of unactivated 1-alkenes as well as the H isotope exchange under mild conditions, tentatively via the terminal Ca-H bond of cation monomer LCaH . In this DFT mechanistic work, a novel substrate-dependent catalytic mechanism is disclosed involving cooperative Ca-H-Ca bridges for H isotope exchange, competitive Ca-H-Ca bridges and terminal Ca-H bonds for anti-Markovnikov addition of unactivated 1-alkenes, and terminal Ca-H bonds for Markovnikov addition of conjugation-activated styrene. THF-coordination plays a key role in favoring the anti-Markovnikov addition while strong cation-π interactions direct the Markovnikov addition to terminal Ca-H bonds.
最近，研究表明，双 Ca-H-Ca 桥联氢化钙阳离子二聚体配合物 [LCaH CaL]（大环配体 L=NNNN-四齿 Me TACD）在温和条件下显著催化非活化 1-烯烃的加氢以及 H 同位素交换反应，这可能是通过阳离子单体 LCaH 的末端 Ca-H 键实现的。在这项 DFT 机理研究中，揭示了一种新的底物依赖性催化机理，涉及协同 Ca-H-Ca 桥促进 H 同位素交换，竞争性 Ca-H-Ca 桥和末端 Ca-H 键促进非活化 1-烯烃的反 Markovnikov 加成，以及末端 Ca-H 键促进共轭活化苯乙烯的 Markovnikov 加成。THF 配位在有利于反 Markovnikov 加成方面起着关键作用，而强阳离子-π 相互作用则将 Markovnikov 加成引导至末端 Ca-H 键。
