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A New Approach to the Design of Neutral 10-C-5 Trigonal-Bipyramidal Carbon Compounds: A “π-Electron Cap” Effect

Authors

  • Prof. Valery F. Sidorkin,

    Corresponding author
    1. A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Favorsky, 1, Irkutsk 664033 (Russian Federation), Fax: (+7) 3952-419346
    • A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Favorsky, 1, Irkutsk 664033 (Russian Federation), Fax: (+7) 3952-419346

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  • Dr. Evgeniya P. Doronina,

    1. A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Favorsky, 1, Irkutsk 664033 (Russian Federation), Fax: (+7) 3952-419346
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  • Dr. Elena F. Belogolova

    1. A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Favorsky, 1, Irkutsk 664033 (Russian Federation), Fax: (+7) 3952-419346
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Abstract

DFT (B3LYP, M06-2X) and MP2 methods are applied to the design of a wide series of the potentially 10-C-5 neutral compounds based on 6-azabicyclotetradecanes: XC1(YCH2CH2CH2)3N 13, XC1(YC6H4CH2)3N 46, XC1[Y(tBuC6H3)CH2]3N 79 and carbatranophanes

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1025 (X=Me, F, Cl; Y=O, NH, CH2, SiH2; Z=O, CH2, (CH2)2, (CH2)3). Carbatranophanes 1025 are characterized by a sterical compression of their axial 3c–4e XC1←N fragment with respect to that in the parent molecules 46. A magnitude of the revealed effect depends on a valence surrounding of the central carbon atom C1, the size and the nature of the side chains (Z) that link the “π-electron cap” with a tetradecane backbone. This circumstance allowed us to obtain 10-C-5 structures with the configuration of the bonds around the C1 atom, which corresponds to practically an ideal trigonal bipyramid. In these compounds, the values of the covalence ratio χmath formula of approximately 0.6 for the coordination C1←N contacts with a covalent contribution (atoms in molecules (AIM) and natural bond orbital (NBO)) are record in magnitude. These values lie close to a low limit of the interval of the χSi←D change (0.6–0.9) being characteristic of the dative and ionic-covalent (by nature) Si←D bond (D=N, O) in the known 10-Si-5 silicon compounds.

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