The Aromaticity of Polyphosphaphospholes Decreases with the Pyramidality of the Tricoordinate Phosphorus

Alk Dransfeld, L. Nyulászi, Paul Ragué Von Schleyer

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Abstract

The aromaticity of phospholes, Pn (CH)4-nPH with n = 0-4, becomes larger as the number of dicoordinate atoms (n) in the ring increases. This is due to the decreasing pyramidality of the tricoordinate phosphorus. The aromaticity is shown by various criteria, e.g., the nucleus-independent chemical shifts (NICS), and the separated π contribution NICS(π), as well as the Bird aromaticity (BI) and the bond-shortening (BDSHRT) indexes. The change of the aromaticity is correlated with the bond angle sum (the degree of planarity) about the tricoordinate phosphorus (e.g., correlation coefficient = 0.968 with NICS). The aromaticities of the planar Pn(CH)4-ffPH phospholes (first-order saddle points for n = 0-3, minimum for n = 4) (NICS values between -15.4 and -17.4 ppm) all are similar. The same is true for the NICS (-12.3 to -15.9) aromaticity of the phospholyl anions (Pn(CH)4-nP-), n = 0-4, which are close to those of the planar phospholes. According to NICS, BI and BDSHRT planar phospholes are more aromatic than pyrrol or thiophene. Isodesmic reaction energies do not correlate with the bond angle sum, since the energy cost of the increasing planarization of the tricoordinate phosphorus consumes the stabilization achieved by aromaticity.

Original languageEnglish
Pages (from-to)4413-4420
Number of pages8
JournalInorganic Chemistry
Volume37
Issue number17
Publication statusPublished - 1998

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Chemical shift
Phosphorus
chemical equilibrium
phosphorus
nuclei
methylidyne
Thiophenes
birds
Chemical bonds
Birds
saddle points
chemical bonds
thiophenes
correlation coefficients
Anions
Stabilization
stabilization
anions
costs
Atoms

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

The Aromaticity of Polyphosphaphospholes Decreases with the Pyramidality of the Tricoordinate Phosphorus. / Dransfeld, Alk; Nyulászi, L.; Von Schleyer, Paul Ragué.

In: Inorganic Chemistry, Vol. 37, No. 17, 1998, p. 4413-4420.

Research output: Contribution to journalArticle

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