Rhombic C4. Does it contain the shortest nonbonding C-C distance?

Koop Lammertsma, Osman F. Güner, Pamidighantam V. Sudhakar

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11 Citations (Scopus)


In this ab initio molecular orbital study the bonding properties between the inverted carbons in rhombic C4 and [1.1.1]propellane are discussed. Rhombic C4, its protonated forms C4H + and C4H22+, and its linear isomer have been studied with the 6-311G(2d,p) basis set and all electron correlation using Møller-Plesset perturbation theory at second order. The rhombic form of C4 is estimated to be essentially isoenergetic with the linear form; the estimated harmonic vibrational frequencies for both are compared with experimental data. The molecular orbital and topological one-electron density analyses show that the cross-ring bond of rhombic C 4 is topologically unstable (at various levels of theory) which suggests a frozen transition for C-C bond making/breaking. At MP4 (SDTQ) this cross-ring distance is only 1.546 Å. The stabilizing properties of rhombic C4 (and C4H+, and C4H2+) are compared with those of the well known [1.1.1] propellane, which at MP2/6-31G* has a longer cross-ring bond.

Original languageEnglish
Pages (from-to)8105-8111
Number of pages7
JournalJournal of Chemical Physics
Issue number12
Publication statusPublished - 1991
Externally publishedYes

ASJC Scopus subject areas

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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