Rh⁺n（n = 1 - 30）团簇上烷烃的C - H活化：脱氢反应中的尺寸效应

C-H activation of alkanes on Rh+ n (n=1-30) clusters: size effects on dehydrogenation.

作者信息

Adlhart Christian, Uggerud Einar

机构信息

Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, N-0315 Oslo, Norway.

出版信息

J Chem Phys. 2005 Dec 1;123(21):214709. doi: 10.1063/1.2131066.

DOI:10.1063/1.2131066

PMID:16356063

Abstract

The rate coefficients for the dehydrogenation of ethane, propane, and isobutane with cationic rhodium atoms Rh+ and clusters Rh+ n of up to 30 atoms were measured under single-collision conditions in a Fourier-transform ion cyclotron resonance mass spectrometer. The reaction rates are cluster size dependent and parallel for all the three alkanes. While the reactions proceed close to the theoretical collision rates for a large number of clusters, characteristic minima are observed for Rh+ (5/6/9/19/28). The degree of dehydrogenation varies with the cluster size with maxima for 10< or =n< or =15 for the three alkanes and for n=3 and 2-4 in the cases of ethane and propane, respectively. However, complete dehydrogenation is only observed for the reaction of Rh+ 11 with propane. Dehydrogenation is remarkably selective and no other neutral products than H2 are observed. The results are interpreted in terms of likely cluster geometries.

摘要

在傅里叶变换离子回旋共振质谱仪的单碰撞条件下，测量了乙烷、丙烷和异丁烷与阳离子铑原子Rh⁺以及多达30个原子的团簇Rh⁺ₙ脱氢反应的速率系数。反应速率与团簇大小有关，且这三种烷烃的反应速率呈平行关系。虽然对于大量团簇，反应速率接近理论碰撞速率，但对于Rh⁺(5/6/9/19/28)观察到了特征性的最小值。脱氢程度随团簇大小而变化，三种烷烃在10≤n≤15时出现最大值，乙烷和丙烷分别在n = 3和n = 2 - 4时出现最大值。然而，仅观察到Rh⁺₁₁与丙烷反应完全脱氢。脱氢具有显著的选择性，除了H₂之外未观察到其他中性产物。根据可能的团簇几何结构对结果进行了解释。