title: Is Hexachloro-cyclo-triphosphazene Aromatic? Evidence from Experimental Charge Density Analysis.
abstract: Experimental charge density studies of hexachloro-cyclo-triphosphazene (1) and the boat conformation of octachloro-cyclo-tetraphosphazene (2 a) were performed to unambiguously describe the origin of the electron delocalization in the P3N3ring in 1. The obtained results were compared to DFT studies in the solid state and the gas phase. Electron density analysis revealed a highly polarized nature of the P-N bonds and a modular structure of the P3N3and P4N4rings, which can be separated into independent Cl2PN units with a perfect transferability between the compounds. Further analysis of the source function experimentally proves the presence of negative hyperconjugation involving both out-of-plane and in-plane nitrogen electrons as well as electrons of the chlorine atoms. Finally, these results discard the presence of pseudoaromatic delocalization in the nearly planar P3N3ring.
authors.affiliation: Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Car. Toluca-Atlacomulco km. 14.5, 50200, Toluca, Estado de México, México.
authors.forename: Vojtech
authors.initials: V
authors.lastname: Jancik
authors.affiliation: Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510, México, D.F., México.
authors.forename: Fernando
authors.initials: F
authors.lastname: Cortés-Guzmán
authors.affiliation: Institut für Anorganische Chemie, Universität Göttingen, Tammannstraße 4, 37077, Göttingen, Germany.
authors.forename: Regine
authors.initials: R
authors.lastname: Herbst-Irmer
authors.affiliation: Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM, Car. Toluca-Atlacomulco km. 14.5, 50200, Toluca, Estado de México, México.
authors.forename: Diego
authors.initials: D
authors.lastname: Matínez-Otero
keywords: electron density; hexachloro-cyclo-triphosphazene; hyperconjugation; quantum chemistry; unit transferability