Castro Abril C, Balcells David, Repisky Michal, Helgaker Trygve, Cascella Michele
Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo, Norway.
Hylleraas Centre for Quantum Molecular Sciences, Department of Chemistry, UiT-The Arctic University of Norway, 9037 Tromsø, Norway.
Inorg Chem. 2020 Dec 7;59(23):17509-17518. doi: 10.1021/acs.inorgchem.0c02753. Epub 2020 Nov 23.
H NMR spectroscopy has become an important technique for the characterization of transition-metal hydride complexes, whose metal-bound hydrides are often difficult to locate by X-ray diffraction. In this regard, the accurate prediction of H NMR chemical shifts provides a useful, but challenging, strategy to help in the interpretation of the experimental spectra. In this work, we establish a density-functional-theory protocol that includes relativistic, solvent, and dynamic effects at a high level of theory, allowing us to report an accurate and reliable interpretation of H NMR hydride chemical shifts of iridium polyhydride complexes. In particular, we have studied in detail the hydride chemical shifts of the [Ir(IMe)(CO)H] complex in order to validate previous assignments. The computed H NMR chemical shifts are strongly dependent on the relativistic treatment, the choice of the DFT exchange-correlation functional, and the conformational dynamics. By combining a fully relativistic four-component electronic-structure treatment with ab initio molecular dynamics, we were able to reliably model both the terminal and bridging hydride chemical shifts and to show that two NMR hydride signals were inversely assigned in the experiment.
氢核磁共振光谱已成为表征过渡金属氢化物配合物的重要技术，其与金属相连的氢化物通常难以通过X射线衍射确定位置。在这方面，准确预测氢核磁共振化学位移提供了一种有用但具有挑战性的策略，有助于解释实验光谱。在这项工作中，我们建立了一种密度泛函理论方法，该方法在高水平理论下考虑了相对论、溶剂和动力学效应，使我们能够对铱多氢化物配合物的氢核磁共振氢化物化学位移进行准确可靠的解释。特别是，我们详细研究了[Ir(IMe)(CO)H]配合物的氢化物化学位移，以验证先前的归属。计算得到的氢核磁共振化学位移强烈依赖于相对论处理、密度泛函理论交换相关泛函的选择以及构象动力学。通过将完全相对论四分量电子结构处理与从头算分子动力学相结合，我们能够可靠地模拟末端和桥连氢化物的化学位移，并表明在实验中两个核磁共振氢化物信号的归属是相反的。
