Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
J Am Chem Soc. 2020 Apr 29;142(17):7827-7835. doi: 10.1021/jacs.0c00712. Epub 2020 Apr 17.
Terminal Ni hydrides are proposed intermediates in proton reduction catalyzed by both molecular electrocatalysts and metalloenzymes, but well-defined examples of paramagnetic nickel hydride complexes are largely limited to bridging hydrides. Herein, we report the synthesis of an = 1/2, terminally bound thiolate-Ni-H complex. This species and its terminal hydride ligand in particular have been thoroughly characterized by vibrational and EPR techniques, including pulse EPR studies. Corresponding DFT calculations suggest appreciable spin leakage onto the thiolate ligand. The hyperfine coupling to the terminal hydride ligand of the thiolate-Ni-H species is comparable to that of the hydride ligand proposed for the Ni-C hydrogenase intermediate (Ni--Fe). Upon warming, the featured thiolate-Ni-H species undergoes bimolecular reductive elimination of H. Associated kinetic studies are discussed and compared with a structurally related Fe-H species that has also recently been reported to undergo bimolecular H-H coupling.
端镍氢化物被认为是分子电催化剂和金属酶催化的质子还原反应的中间产物，但具有明确结构的顺磁镍氢化物配合物在很大程度上仅限于桥接氢化物。在此，我们报告了一个 = 1/2，端基硫醇-Ni-H 配合物的合成。该物种及其端氢配体，特别是通过振动和 EPR 技术，包括脉冲 EPR 研究，得到了彻底的表征。相应的密度泛函理论（DFT）计算表明，硫醇配体上有可观的自旋泄露。硫醇-Ni-H 物种与 Ni-C 氢化酶中间体（Ni--Fe）中所提出的氢化物配体的超精细耦合相当。升温时，特征性的硫醇-Ni-H 物种经历双分子氢的还原消除。讨论了相关的动力学研究，并与最近报道的也经历双分子 H-H 偶联的结构相关的 Fe-H 物种进行了比较。
