Construction Principles of "Hyparenes": Families of Molecules with Planar Pentacoordinate Carbons

See allHide authors and affiliations

Science  29 Jun 2001:
Vol. 292, Issue 5526, pp. 2465-2469
DOI: 10.1126/science.1060000

You are currently viewing the abstract.

View Full Text

Log in to view the full text

Log in through your institution

Log in through your institution


Density-functional theory calculations predict that three borocarbon units with planar pentacoordinate carbons −C3B3−, −C2B4−, and −CB5−, can replace the −(CH)3− subunits in aromatic or even in antiaromatic hydrocarbons to construct “hyparenes” (families of molecules with planar pentacoordinate carbons). These borocarbon units contribute two, one, and zero electrons, respectively, to the parent pi system. Depending on the choice of these units, the hyparenes (judging from computed proton and nucleus-independent chemical shifts), can maintain or can interconvert the aromatic or antiaromatic character of the parent compounds. The hyparenes are low-lying local minima with normal carbon-boron, boron-boron, and carbon-carbon bond lengths. The multicenter bonding in the hyparenes involves contributions of partial sigma and partial pi bonds to the planar pentacoordinate carbons; the octet rule is not violated. Borocarbon species, for which there is some mass spectrometric evidence, might be observed and identified, for example, in matrix isolation by vibrational spectroscopy.

  • * Permanent address: Graduate School at Beijing, University of Science and Technology of China, Academia, Sinica, Beijing 10039, People's Republic of China.

  • To whom correspondence should be addressed. E-mail: schleyer{at}

View Full Text