Si₆C₁₈: A bispentalene derivative with two planar tetracoordinate carbons

Abstract

Here we show that substituting the ten protons in the dianion of a bispentalene derivative (C18H102−) by six Si2+ dications produces a minimum energy structure with two planar tetracoordinate carbons (ptC). In Si6C18, the ptCs are embedded in the terminal C5 pentagonal rings and participate in a three‐center, two‐electron (3c‐2e) Si‐ptC‐Si σ‐bond. Our exploration of the potential energy surface identifies a triphenylene derivative as the putative global minimum. Nevertheless, robustness to Born–Oppenheimer molecular dynamics (BOMD) simulations at 900 and 1500 K supports bispentalene derivative kinetic stability. Chemical bonding analysis reveals ten delocalized π‐bonds, which, according to Hückel's 4n + 2 π‐electron rule, would classify it as an aromatic system. Magnetically induced current density analysis reveals the presence of intense local paratropic currents and a weakly global diatropic current, the latter agreeing with the possible global aromatic character of this specie.

Exploring the Potential Energy Surface of Medium-Sized Aromatic Polycyclic Systems with Embedded Planar Tetracoordinate Carbons: A Guided Approach

“…This research delves into the intricate processes of designing and examining the PES of polycyclic systems comprising over twenty atoms featuring ptCs. To address this challenge, we employed a proven design principle [23,[29][30][31][32][33][34][35], to computationally formulate a derivative of Naphtho[1,2-b:4,3-b′:5,6-b′′:8,7-b′′′′]tetrathiophene. This design procedure initiated substituting sulfur atoms with CHunits.…”

“…This substitution was designed to preserve the π-aromatic circuits inherent in the parent aromatic hydrocarbons. This strategy was initially tested on derivatives of small aromatic hydrocarbons, each featuring one or two ptCs [23,[29][30][31][32][33][34][35]. A striking feature of these ptC systems is their global π-aromaticity and three-center, two-electron (3c-2e) E-ptC-E bonds that display localized -aromaticity.…”

Exploring the Potential Energy Surface of Medium-Sized Aromatic Polycyclic Systems with Embedded Planar Tetracoordinate Carbons: A Guided Approach

“…This research delves into the intricate processes of designing and examining the PES of polycyclic systems comprising over twenty atoms featuring ptCs. To address this challenge, we employed a proven design principle [23,[29][30][31][32][33][34][35] Despite not achieving the global minimum (GM), the resultant cluster (1) was a local minimum on the PES. This allowed us to assess a simple but effective strategy to explore its PES (see below).…”

“…This substitution was designed to preserve the π-aromatic circuits inherent in the parent aromatic hydrocarbons. This strategy was initially tested on derivatives of small aromatic hydrocarbons, each featuring one or two ptCs [23,[29][30][31][32][33][34][35]. A striking feature of these ptC systems is their global π-aromaticity and three-center, two-electron (3c-2e) E-ptC-E σ-bonds that display a localized σ-aromaticity.…”

Strong carbon – noble gas covalent bond and fluxionality in hypercoordinate compounds

“…20 These compounds, in conjunction with those hypercoordinated carbon systems, have been studied extensively because of the breaking of the traditional rules that indicate that carbon should form four covalent bonds in a tetrahedral arrangement. [21][22][23][24][25][26][27][28][29] However, to the authors' knowledge, no systematic study of hypercoordinated carbon compounds containing C-Ng s-bonds has been reported to date. The only hypercoordinated compound containing a noble gas atom was reported by Olah and coworkers, who predicted the structure and dissociation in the CH 4 2+ and He components.…”