Perfect planar tetracoordinate carbon in neutral unsaturated hydrocarbon cages: A new strategy utilizing three‐dimensional electron delocalization

Abstract

A new series of unsaturated pure and boron-substituted hydrocarbons containing a perfect planar tetracoordinate carbon (ptC) have been proposed by performing density functional computations. The ptC is effectively stabilized through three-dimensional delocalization of ptC's lone pair into pi-conjugated systems, by utilizing a new strategy opening a brand new way of designing ptC structures. Compared to previously proposed ptC-containing hydrocarbon cage compound, a neutral hydrocarbon designed here might be a more viable target for synthetic attempts.

Four Decades of the Chemistry of Planar Hypercoordinate Compounds

“…[30] Exemplified by 10 a-j (Figure 10), this principle uses two formal anionic -BH 2 -g roups to compensate the formal double positive charges on the ptC.I nt hese compounds,t he ptC p orbitals are the LUMOs.T he "missing" electrons are utilized effectively for bonding.T he HOMO of 10 b (shown in Figure 11) is an example.Asasimple extension of Wang and Schleyers principle,in2009, Wang [37] predicted several unsaturated pure and boron-substituted hydrocarbons containing ap erfectly planar tetracoordinate carbon by means of ac ombined scheme:s tabilized mechanically through the strain of ar igid cage framework, and electronically through the electron delocalization in at hree-dimensional p-conjugated system. Octaboraplane and its key molecularo rbitals.…”

“…The HOMO of 10 b (shown in Figure 11) is an example. As a simple extension of Wang and Schleyer’s principle, in 2009, Wang37 predicted several unsaturated pure and boron‐substituted hydrocarbons containing a perfectly planar tetracoordinate carbon by means of a combined scheme: stabilized mechanically through the strain of a rigid cage framework, and electronically through the electron delocalization in a three‐dimensional π‐conjugated system.…”

Vier Jahrzehnte Chemie der planar hyperkoordinierten Verbindungen

“…Das HOMO von 10 b (Abbildung 11) ist dafür ein Beispiel. Mit einer einfachen Erweiterung des Prinzips sagte Wang37 im Jahre 2009 mehrere ungesättigte reine und borsubstituierte Kohlenwasserstoffe voraus, die ein perfekt planar tetrakoordiniertes Kohlenstoffatom aufgrund eines kombinierten Ansatzes enthielten: mechanische Stabilisierung durch ein starres Käfiggerüst und elektronische Stabilisierung durch die Elektronendelokalisierung in einem dreidimensionalen konjugierten π‐System.…”

How to Accomplish a Square C(N)4 Substructure of the Planar Tetracoordinate Carbon

“…5a In 2009, Wang reported several molecules containing a perfectly ptC(C) 4 substructure using the "charge compensation" and the "mechanical" strategies and stabilized the molecules in two ways: by using the electron delocalization in a threedimensional π-conjugated system electronically and the strain of a rigid cage framework mechanically. 8 Ordinarily, the "charge-compensation" and the "mechanical" strategies are useful approaches to achieve the ptC arrangements. However, the charge compensation by using the electron-deficient groups, such as BH 2 , would be unworkable to achieve a ptC(N) 4 substructure.…”