The Local Kinetic Energy Profile of an Inverted CarbonCarbon Bond Reveals and Refines its Charge‐Shift Character

Abstract

Analysis of the kinetic energy density within a molecule identifies patterns in its electronic structure that are linked to the concept of charge-shift bonding. This is illustrated in a detailed study of twelve molecules, possessing carbon-carbon covalent as well as carbon-carbon charge-shift bonds in various degrees of orders, including propellanes and heteropropellanes. Regions of slow electrons are fundamental for such a correlation, and a RoSE (region of slow electrons) indicator ν(±), based on the positive definite kinetic energy density τ, is employed to characterize classes of charge-shift bonds in terms of its full topology of all critical points of rank three.

Computational Modeling of the Feasibility of Substituted [1.1.1]Propellane Formation from Anionic Bridgehead Bromide Precursors

“…Values in parenthesis correspond to values calculated in an identical manner by Pittman bu using the CCSD/aug-cc-pVDZ method [8]. 4 Strain energy of the central bridgehead-bridgehead bond relative to unsubstituted 1 as calculated according to isodesmic Equations ( 4)-( 6). 5 Thi [1.1.1]propellane was not a stationary point on the potential energy surface at the ωB97X-D/aug-cc pVDZ level of theory.…”

“…[1.1.1]Propellane, 1 (Figure 1), a compound whose structure includes two saturated carbons in which all four bonds are directed into a single hemisphere, was first synthesized in 1982 by Wiberg [1]. While 1 remains a target of fascination for theoretical chemists because of the unusual bonding arrangement between the two inverted bridgehead carbons [2][3][4][5], it has also seen recent practical applications for a variety of synthetic purposes [6,7]. There has been ongoing interest in the possibility of synthesizing mono-, di-, and trisubstituted [1.…”

“…Total strain energy of the propellane relative to unsubstituted 1 according to isodesmic Equations (1)-(3). Values in parenthesis correspond to values calculated in an identical manner by Pittman but using the CCSD/aug-cc-pVDZ method[8] 4. Strain energy of the central bridgehead-bridgehead bond relative to unsubstituted 1 as calculated according to isodesmic Equations (4)-(6) 5.…”

Laplacian of the Hamiltonian Kinetic Energy Density as an Indicator of Binding and Weak Interactions

“…Jacobsen describes CS bond as "a bond that behaves chemically as a covalent bond, despite the fact that the forming atoms exhibit an ionic charge distribution". [70] CS shows large covalent-ionic resonance interaction energy, and depleted charge densities at bond critical points. Jacobsen used the topology analysis of kinetic energy densities to evaluate the CS nature of carbon-carbon bonds in highly strained situations.…”