X-ray absorption methods for the determination of Ru-Cl bond covalency in olefin metathesis catalysts: On the normalization of chlorine K-edges in ruthenium complexes
X-ray absorption methods for the determination of Ru-Cl bond covalency in olefin metathesis catalysts: On the normalization of chlorine K-edges in ruthenium complexes
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DOI：
10.1016/j.ica.2005.12.058
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发表时间：
2006-06-01
影响因子：
2.8
通讯作者：
Kennepohl, Pierre
中科院分区：
文献类型：
--
作者：
Delgado-Jaime, Mario Ulises;Conrad, Jay C.;Kennepohl, Pierre
系统地介绍了一种定量分析Ru络合物中ClK边XAS光谱的方法，并将其应用于催化烯烃歧化反应的Ru卡宾络合物。这种方法一般很适合于探测配体给体对空过渡金属d轨道的贡献，但如L-2，L-3边的重叠使这类络合物的探测变得非常困难。提出了一种从氯钾边谱中去除如L-2、L-3边的方法，并进行了实验。归一化过程利用了分离良好的Ru L-2边和适当的L-3/L-2分支比，明确地去除了这些边的贡献，并允许准确地归一化ClK-边光谱。还描述了一种广义背景减法，它解释了所涉及的大能量范围内的可变性。只要自旋-轨道分裂金属(L或M-)边缘的一个分量不受干扰，这种方法对于任何类似的重叠边缘都应该是通用的。这项研究的结果表明，根据催化剂的性质，Ru-Cl键有很大的差异。(C)2006爱思唯尔B.V.保留所有权利。
A systematic approach to quantitative analysis of Cl K-edge XAS spectra in ruthenium complexes is outlined and applied to ruthenium carbene complexes involved in olefin metathesis catalysis. This method is generally well-suited for probing ligand donor contributions into empty transition metal d orbitals, but overlap of the Ru L-2,L-3 edge makes this very difficult in these complexes. A method for removing the Ru L-2,L-3 edges from the Cl K-edge spectrum is developed and tested. The normalization procedure makes use of the well-separated Ru L-2 edge and an appropriate L-3/L-2 branching ratio to unambiguously remove contributions from these edges and allow for accurate normalization of the Cl K-edge spectrum. A generalized background subtraction that accounts for variability over the large energy range involved is also described. The methodology should be general for any similarly overlapping edges, as long as one component of the spin-orbit split metal (L- or M-) edge is unperturbed. The results of this study indicate a substantial difference in Ru-Cl bonding depending on the nature of the catalyst. (c) 2006 Elsevier B.V. All rights reserved.