Issue 40, 2018

Halogen bond shortens and strengthens the bridge bond of [1.1.1]propellane and the open form of [2.2.2]propellane

Abstract

Detailed electronic structural analysis of [1.1.1]propellane and the open form of [2.2.2]propellane, especially their highest occupied molecular orbital (HOMO), shows the existence of significant electronic congestion at their bridge bond. The HOMO of [1.1.1]propellane is a spread-out orbital of its inverted tetrahedral bridgehead atoms. The HOMO of the open form of [2.2.2]propellane is an anti-bonding combination of its bridgehead atoms due to the stabilizing through-bond interaction. This unique spatial disposition of the HOMO enables a high electron density at the bridgehead atoms. Herein, we utilize the electron scavenging power of halogen bond donors to extract a fraction of destabilizing electrons from the bridge bond with the aim to alleviate its electronic congestion, which results in shortening and strengthening of the bridge bond with a reduction in the bond order. This result answers the seminal question raised by K. B. Wiberg in 1983, how can one have a relatively ‘strong bond’ without much bonding character?”

Graphical abstract: Halogen bond shortens and strengthens the bridge bond of [1.1.1]propellane and the open form of [2.2.2]propellane

Supplementary files

Article information

Article type
Paper
Submitted
11 Aug 2018
Accepted
19 Sep 2018
First published
20 Sep 2018

Phys. Chem. Chem. Phys., 2018,20, 25792-25798

Halogen bond shortens and strengthens the bridge bond of [1.1.1]propellane and the open form of [2.2.2]propellane

J. Joy, E. Akhil and E. D. Jemmis, Phys. Chem. Chem. Phys., 2018, 20, 25792 DOI: 10.1039/C8CP05125A

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