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@article{725894,
author = {Kapička, Libor and Kubáček, Pavel and Holub, Petr},
article_location = {Amsterdam},
article_number = {1-3},
keywords = {Cyclic phosphazenes; Aromaticity; Orbital interactions; Potential energy surface},
language = {eng},
issn = {0166-1280},
journal = {Journal of Molecular Structure (Theochem)},
title = {Bonding and aromaticity of cyclic phosphazenes viewed as interaction of Dnh fragments},
url = {https://www.sciencedirect.com/science/article/pii/S0166128007004344},
volume = {820},
year = {2007}
}
TY - JOUR
ID - 725894
AU - Kapička, Libor - Kubáček, Pavel - Holub, Petr
PY - 2007
TI - Bonding and aromaticity of cyclic phosphazenes viewed as interaction of Dnh fragments
JF - Journal of Molecular Structure (Theochem)
VL - 820
IS - 1-3
SP - 148-158
EP - 148-158
PB - Elsevier Science
SN - 01661280
KW - Cyclic phosphazenes
KW - Aromaticity
KW - Orbital interactions
KW - Potential energy surface
UR - https://www.sciencedirect.com/science/article/pii/S0166128007004344
L2 - https://www.sciencedirect.com/science/article/pii/S0166128007004344
N2 - The qualitative molecular orbital approach based on orbital interactions was used to explore the nature of bonding in cyclic fluorophosphazenes (F2PN)n, where n is 2-6. Besides the classical skeleton of sigma-bonds, only two, one radial and one axial, 2n-center two-electron pi-bonds significantly participate in the extra stabilization of the (PN)n ring. The pi-radial interaction is more effective and comparable by size with the sigma ones. Additional slight stabilization of a (PN)n ring is achieved by nonbonding pi-radial and pi-axial molecular orbitals (MOs) which are mainly localized on nitrogen atoms. The orbital interactions have a hyperconjugation character. The bonding energy decomposition analysis showed that the cyclic interactions are about half covalent and half electrostatic. The covalent bonding is dominated by radial interactions. The aromaticity concept is not appropriate for description of bonding in cyclophosphazenes. The contribution of phosphorus d atomic orbitals to the concept of chemical bonding in phosphazenes is negligible, but the inclusion of d phosphorus functions in a basis set is appropriate for a correct quantitative description of electronic and geometric structure. Extended Hückel (EHT), ab initio and density functional (DFT) calculations provide the same qualitative picture of the bonding. The very flat B3LYP/6-311+G(3df)//B3LYP/6-31G(3df) potential energy surface (PES) with the low energy barrier (1.6 kJ mol-1) indicates the very fast and easy conformational motion of (F2PN)4. The global minimum on this PES is the S4 conformation.
ER -
KAPIČKA, Libor, Pavel KUBÁČEK a Petr HOLUB. Bonding and aromaticity of cyclic phosphazenes viewed as interaction of Dnh fragments. \textit{Journal of Molecular Structure (Theochem)}. Amsterdam: Elsevier Science, roč.~820, 1-3, s.~148-158. ISSN~0166-1280. 2007.
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