Halogen bond shortens and strengthens the bridge bond of [1.1.1]propellane and the open form of [2.2.2]propellane. Issue 40 (4th October 2018)

• Record Type: Journal Article
• Authors: Joy, Jyothish; Akhil, Edakkandy; Jemmis, Eluvathingal D.
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 40(2018)
• Page Start: 25792
• Page End: 25798
• Publication Date: 2018-10-04
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c8cp05125a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : The electron scavenger property of halogen bond donors is employed to stabilize the bridge-bond of [1.1.1]propellane and o -[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?"