Wu Haiming, Jia Yuhan, Zhao Xiaoyun, Geng Lijun, Lin Shiquan, Li Si-Dian, Luo Zhixun
Beijing National Laboratory for Molecular Science (BNLMS), State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Department of Chemistry, Tsinghua University, Beijing 100084, China.
J Phys Chem A. 2024 Feb 22;128(7):1274-1279. doi: 10.1021/acs.jpca.3c08337. Epub 2024 Feb 9.
Iodomethane and bromomethane (CHI/CHBr) are common chemicals, but their chemistry on nanometals is not fully understood. Here, we analyze the reactivity of Rh ( = 3-30) clusters with halomethanes and unveil the spin effect and concentration dependence in the C-H and C-X bond activation. It is found that the reactions under halomethane-rich conditions differ from those under metal-rich conditions. Both CHI and CHBr undergo similar dehydrogenation on the Rh clusters in the presence of small quantity reactants; however, different reactions are observed in the presence of sufficient CHI/CHBr, showing dominant Rh(CHBr) ( = 1-4) products but a series of RhCHI species ( = 1-4, = 1-12, and = 1-5) pertaining to H, HI, or CH removal. Density functional theory calculations reveal that the dehydrogenation and demethanation of CHBr are relatively less exothermic and will be deactivated by sufficient gas collisions if helium cooling takes away energy immediately; instead, the successive adsorption of CHBr gives rise to a series of Rh(CHBr) species with accidental C-Br bond dissociation.
碘甲烷和溴甲烷（CHI/CHBr）是常见的化学品，但它们在纳米金属上的化学反应尚未完全了解。在此，我们分析了Rh（= 3 - 30）团簇与卤代甲烷的反应活性，并揭示了C - H和C - X键活化中的自旋效应和浓度依赖性。研究发现，富卤代甲烷条件下的反应与富金属条件下的反应不同。在少量反应物存在的情况下，CHI和CHBr在Rh团簇上都经历类似的脱氢反应；然而，在有足够的CHI/CHBr存在时，会观察到不同的反应，主要生成Rh(CHBr)（= 1 - 4）产物，但会出现一系列与H、HI或CH去除相关的RhCHI物种（= 1 - 4、= 1 - 12和= 1 - 5）。密度泛函理论计算表明，CHBr的脱氢和脱甲烷反应放热相对较少，如果氦气冷却能立即带走能量，这些反应会因足够的气体碰撞而失活；相反，CHBr的连续吸附会导致一系列Rh(CHBr)物种意外发生C - Br键解离。
