Chemical Bonding in a Linear Chromium Metal String Complex

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• 作者：Lai-Chin Wu ; Maja K. Thomsen ; Solveig R. Madsen ; Mette Schmoekel ; Mads R. V. J酶rgensen ; Ming-Chuan Cheng ; Shie-Ming Peng ; Yu-Sheng Chen ; Jacob Overgaard ; Bo B. Iversen
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：December 1, 2014
• 年：2014
• 卷：53
• 期：23
• 页码：12489-12498
• 全文大小：576K
• ISSN：1520-510X

文摘

A combined experimental and theoretical electron density study of the shortest trichromium metal wire, Cr₃(dpa)₄Cl₂路(C₂H₅OC₂H₅)_x(CH₂Cl₂)_1鈥?i>x (1, dpa = bis(2-pyridyl)amido), is reported. High resolution X-ray diffraction data has been collected both at 100 K using a conventional X-ray source (DS1) and at 15 K using a synchrotron X-ray source (DS2). The linear chromium string is terminated by Cl^{鈥?/sup> ions at both ends, and each Cr atom is also coordinated by four N atoms from bridging dpa ligands. The two Cr鈥揅r bond distances are unequal at 100 K (with d(Cr1鈥揅r2) being 0.029 脜 shorter than d(Cr2鈥揅r3)) but at 15 K they are almost equal (0.002 脜 difference). Analysis of the slightly elongated thermal ellipsoids of the Cr2 atom suggests that it is not due to disorder, but the presence of a shallow potential energy surface. Laplacian maps clearly show local valence shell charge concentration (VSCC) in the electron density along the bisector of the equatorial Cr鈥揘 bonds. Integration over the atomic basins indicates that Cr2 has smaller atomic charge and volume than Cr1 and Cr3. The topological characterization of the Cr鈥揅r bonds indicates partly covalent characters with electron density at the bond critical point of 鈭?.3 e 脜鈥? and negative total energy density. The delocalization index of Cr鈥揅r is 0.8 for Cr1鈥揅r2 and 0.08 for Cr1鈥揅r3. Second-order perturbation analysis shows high stabilization energy of the Cr鈥揅r bonds (E(2) 鈭?190 kcal mol鈥?). Delocalization indices and source function and natural bond orbital analyses are all indicative of localized Cr鈥揅r bonding interactions.}