Theoretical Prediction on [5]Radialene Sandwich Complexes (CpM)2(C10H10) (Cp = η5-C5H5; M = Fe, Co, Ni): Geometry, Spin States, and Bonding

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• 作者：Nan-nan LiuYing-ying Xue ; Yi-hong Ding
• 刊名：Journal of Physical Chemistry A
• 出版年：2017
• 出版时间：February 9, 2017
• 年：2017
• 卷：121
• 期：5
• 页码：1106-1112
• 全文大小：689K
• ISSN：1520-5215

文摘

[5]Radialene, the missing link for synthesis of radialene family, has been finally obtained via the preparation and decomplexation of the [5]radialene–bis-Fe(CO)₃ complex. The stability of [5]radialene complex benefits from the coordination with Fe(CO)₃ by losing free 1,3-butadiene structures to avoid polymerization. In light of the similar coordination ability of half-sandwiches CpM(Cp = η⁵-C₅H₅; M = Fe, Co, Ni), there is a great possibility that the sandwiched complexes of [5]radialene with CpM are available. Herein, we present the first theoretical prediction on the geometry, spin states and bonding of (CpM)(C₁₀H₁₀) and (CpM)₂(C₁₀H₁₀). For M = Fe, Co, Ni, the ground states of (CpM)(C₁₀H₁₀) and (CpM)₂(C₁₀H₁₀) are doublet and triplet, singlet and singlet, and doublet and triplet states, where each Fe, Co, and Ni adopts 17, 18, and 19 electron-configuration, respectively. In particular, (CpFe)₂(C₁₀H₁₀) and (CpNi)₂(C₁₀H₁₀) have considerable open-shell singlet features. Generally the trans isomers of (CpM)₂(C₁₀H₁₀) with two CpM fragments on the opposite sides of the [5]radialene plane are apparently more stable than the cis ones with CpM fragments on the same side. However, for the singlet and triplet isomers of (CpNi)₂(C₁₀H₁₀) (both cis and trans isomers), the energy differences are relatively small, indicating that these isomers all have the opportunity to exist. Besides, the easy Diels–Alder (DA) dimerization between the [3]dendralene-like fragments of (CpM)(C₁₀H₁₀) suggests the great difficulty in isolating the (CpM)(C₁₀H₁₀) monomer.