Miloserdov Fedor M, Rajabi Nasir A, Lowe John P, Mahon Mary F, Macgregor Stuart A, Whittlesey Michael K
Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, U.K.
Institute of Chemical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K.
J Am Chem Soc. 2020 Apr 1;142(13):6340-6349. doi: 10.1021/jacs.0c01062. Epub 2020 Mar 17.
Reaction of [Ru(PPh)HCl] with LiCHTMS, MgMe, and ZnMe proceeds with chloride abstraction and alkane elimination to form the bis-cyclometalated derivatives [Ru(PPh)(CHPPh)H][M'] where [M'] = [Li(THF)] (), [MgMe(THF)] (), and [ZnMe] (), respectively. In the presence of 12-crown-4, the reaction with LiCHTMS yields [Ru(PPh)(CHPPh)H][Li(12-crown-4)] (). These four complexes demonstrate increasing interaction between M' and the hydride ligand in the [Ru(PPh)(CHPPh)H] anion following the trend (no interaction) < < < both in the solid-state and solution. Zn species is present as three isomers in solution including square-pyramidal [Ru(PPh)(CHPPh)(ZnMe)] (), that is formed via C-H reductive elimination and features unsaturated Ru and Zn centers and an axial Z-type [ZnMe] ligand. A [ZnMe] adduct of , [Ru(PPh)(CHPPh)(ZnMe)][BAr] () can be trapped and structurally characterized. reacts with H at -40 °C to form [Ru(PPh)(H)(ZnMe)], , and contrasts the analogous reactions of , , and that all require heating to 60 °C. This marked difference in reactivity reflects the ability of Zn to promote a rate-limiting C-H reductive elimination step, and calculations attribute this to a significant stabilization of via Ru → Zn donation. therefore acts as a latent source of and this operational "dual unsaturation" highlights the ability of Zn to promote reductive elimination in these heterobimetallic systems. Calculations also highlight the ability of the heterobimetallic systems to stabilize developing protic character of the transferring hydrogen in the rate-limiting C-H reductive elimination transition states.
[Ru(PPh)HCl] 与 LiCHTMS、MgMe 和 ZnMe 反应时，会发生氯原子抽取和烷烃消除反应，形成双环金属化衍生物 [Ru(PPh)(CHPPh)H][M']，其中 [M'] 分别为 [Li(THF)] ()、[MgMe(THF)] () 和 [ZnMe] ()。在 12-冠-4 存在的情况下，与 LiCHTMS 的反应会生成 [Ru(PPh)(CHPPh)H][Li(12-冠-4)] ()。这四种配合物表明，在固态和溶液中，M' 与 [Ru(PPh)(CHPPh)H] 阴离子中的氢化物配体之间的相互作用按照 (无相互作用) < < < 的趋势增强。锌物种 在溶液中以三种异构体形式存在，包括四方锥型的 [Ru(PPh)(CHPPh)(ZnMe)] ()，它是通过 C-H 还原消除形成的，具有不饱和的 Ru 和 Zn 中心以及轴向 Z 型 [ZnMe] 配体。 的 [ZnMe] 加合物 [Ru(PPh)(CHPPh)(ZnMe)][BAr] () 可以被捕获并进行结构表征。 在 -40 °C 下与 H 反应形成 [Ru(PPh)(H)(ZnMe)]， ，这与 、 和 的类似反应形成对比，后三者都需要加热到 60 °C。这种显著的反应活性差异反映了锌促进限速 C-H 还原消除步骤的能力，计算结果将此归因于通过 Ru→Zn 供体对 的显著稳定作用。 因此充当了 的潜在来源，这种操作性的“双重不饱和”突出了锌在这些异双金属体系中促进还原消除的能力。计算结果还突出了异双金属体系在限速 C-H 还原消除过渡态中稳定转移氢不断发展的质子性质的能力。
