Limited Occurrence of Isocloso Deltahedra with 9 to 12 Vertices in Low-Energy Hypoelectronic Diferradicarbaborane Structures

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• 作者：Alexandru Lupan ; R. Bruce King
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：October 3, 2011
• 年：2011
• 卷：50
• 期：19
• 页码：9571-9577
• 全文大小：929K
• 年卷期：v.50,no.19(October 3, 2011)
• ISSN：1520-510X

文摘

Theoretical studies show that the 10-vertex system Cp₂Fe₂C₂B₆H₈ is the only one of the 2n skeletal electron Cp₂Fe₂C₂B_n鈥?H_n鈥? systems (n = 9, 10, 11, 12) for which a true isocloso deltahedron having a single degree 6 vertex is highly favored over alternative structures. This is demonstrated by the occurrence of only the 10-vertex isocloso deltahedron as the central Fe₂C₂B₆ polyhedron in all nine of the Cp₂Fe₂C₂B₆H₈ structures within 8 kcal/mol of the global minimum. Low energy isocloso structures are also observed for the 11-vertex Cp₂Fe₂C₂B₇H₉. However, interspersed with these isocloso structures are Cp₂Fe₂C₂B₇H₉ structures based on deltahedra having two or more degree 6 vertices. For the 12-vertex Cp₂Fe₂C₂B₈H₁₀, the six lowest energy structures all have central Fe₂C₂B₈ deltahedra with two degree 6 vertices, one for each iron atom. The Cp₂Fe₂C₂B₈H₁₀ structures having a central Fe₂C₂B₈ icosahedron with all degree 5 vertices lie at significantly higher energies, starting at 17.8 kcal/mol above the global minimum. The 9-vertex Cp₂Fe₂C₂B₅H₇ system appears to be too small for isocloso structures to be favorable, although three such structures are found at energies between 5.5 and 8.0 kcal/mol above the global minimum. Five Cp₂Fe₂C₂B₅H₇ structures based on the tricapped trigonal prism lie in an energy below the lowest energy isocloso structure. The lowest energy Cp₂Fe₂C₂B₅H₇ structure and two higher energy structures within 8.0 kcal/mol of the global minimum have central Fe₂C₂B₅ deltahedra with a degree 6 vertex for each iron atom.