KAPIČKA, Libor, Pavel KUBÁČEK and Petr HOLUB. Bonding and aromaticity of cyclic phosphazenes viewed as interaction of Dnh fragments. Journal of Molecular Structure (Theochem), Amsterdam: Elsevier Science, 2007, vol. 820, 13, p. 148158. ISSN 01661280. 
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@article{725894, author = {Kapička, Libor and Kubáček, Pavel and Holub, Petr}, article_location = {Amsterdam}, article_number = {13}, keywords = {Cyclic phosphazenes; Aromaticity; Orbital interactions; Potential energy surface}, language = {eng}, issn = {01661280}, 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  13 SP  148158 EP  148158 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 26. Besides the classical skeleton of sigmabonds, only two, one radial and one axial, 2ncenter twoelectron pibonds significantly participate in the extra stabilization of the (PN)n ring. The piradial interaction is more effective and comparable by size with the sigma ones. Additional slight stabilization of a (PN)n ring is achieved by nonbonding piradial and piaxial 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/6311+G(3df)//B3LYP/631G(3df) potential energy surface (PES) with the low energy barrier (1.6 kJ mol1) 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 and Petr HOLUB. \textit{Bonding and aromaticity of cyclic phosphazenes viewed as interaction of Dnh fragments}. \textit{Journal of Molecular Structure (Theochem)}, Amsterdam: Elsevier Science, 2007, vol.~820, 13, p.~148158. ISSN~01661280.
