Cyclobutane dication, (CH2)4 2+: a model for a two-electron four-center (2e-4c) Woodward-Hoffmann frozen transition state

G K Surya Prakash; Golam Rasul

doi:10.3762/bjoc.15.148

Cyclobutane dication, (CH₂)₄ ²⁺: a model for a two-electron four-center (2e-4c) Woodward-Hoffmann frozen transition state

Beilstein J Org Chem. 2019 Jul 3:15:1475-1479. doi: 10.3762/bjoc.15.148. eCollection 2019.

Authors

G K Surya Prakash¹, Golam Rasul¹

Affiliation

¹ Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, University Park, Los Angeles, CA 90089-1661, USA.

Abstract

The structures of the elusive cyclobutane dication, (CH₂)₄ ²⁺, were investigated at the MP2/cc-pVTZ and CCSD(T)/cc-pVTZ levels. Calculations show that the two-electron four-center (2e-4c) bonded structure 1 involving four carbon atoms is a minimum. The structure contains formally two tetracoordinate and two pentacoordinate carbons. The non-classical σ-delocalized structure can be considered as a prototype for a 2e-4c Woodward-Hoffmann frozen transition state. The planar rectangular shaped structure 2 with a 2e-4c bond was found not to be a minimum.

Keywords: 2e-4c bond; Woodward–Hoffmann rule; cyclobutane dication; frozen transition state.