Kozubal Justine, Heck Tristan, Metz Ricardo B
Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States.
J Phys Chem A. 2020 Oct 8;124(40):8235-8245. doi: 10.1021/acs.jpca.0c07027. Epub 2020 Sep 24.
Vibrational spectra of the entrance channel complexes Zr(CH)(Ar) ( = 1-2) and Zr(CH) ( = 3-4) and the reaction products ZrCH, ZrCH, ZrCH, and ZrCH in the C-H stretching region (2550-3100 cm) are obtained using photofragment spectroscopy. The experimental spectra and simulations based on calculations at the B3LYP/aug-cc-pVTZ level of theory work together to identify the structures of the ions. The = 1-3 entrance channel complexes show peaks around 2800 and 3000 cm which indicates methane η hydrogen coordination, while the = 4 complex has two peaks around 2800 cm indicative of methane η hydrogen coordination. Observation of the low-frequency C-H stretch of an agostic carbene group, as well as the high-frequency H-H stretch, also confirms production of (H)ZrCH(CH) ( = 1-2) exit channel complexes. The observed C-H activation products formally correspond to loss of H from Zr(CH) and loss of H, H, and H + H from Zr(CH). Comparison of experiment and simulations indicates that the activation products are Zr(CH)(CH), Zr(CH)(CH), Zr(CH)(CH), and HZrCH+(CH) and/or ZrCH(CH).
利用光碎片光谱法获得了入口通道配合物Zr(CH)(Ar)（ = 1 - 2）和Zr(CH)（ = 3 - 4）以及反应产物ZrCH、ZrCH、ZrCH和ZrCH在C - H伸缩区域（2550 - 3100 cm）的振动光谱。基于B3LYP/aug - cc - pVTZ理论水平计算的实验光谱和模拟结果共同确定了离子的结构。 = 1 - 3的入口通道配合物在2800和3000 cm附近出现峰，这表明存在甲烷η氢配位，而 = 4的配合物在2800 cm附近有两个峰，表明存在甲烷η氢配位。对一个闭壳型卡宾基团的低频C - H伸缩以及高频H - H伸缩的观察，也证实了(H)ZrCH(CH)（ = 1 - 2）出口通道配合物的生成。观察到的C - H活化产物形式上对应于Zr(CH)中H的损失以及Zr(CH)中H、H和H + H的损失。实验与模拟的比较表明，活化产物为Zr(CH)(CH)、Zr(CH)(CH)、Zr(CH)(CH)以及HZrCH+(CH)和/或ZrCH(CH)。
