Planar Hexacoordinate Carbons: Half Covalent Half Ionic

Abstract

<div>The global minima of thirteen combinations of atoms with formula CE<sub>3</sub>M<sub>3</sub><sup>+</sup> (E=S-Te and M=Li-Cs) adopt a planar structure with carbon covalently bonded to three chalcogens and ionically bonded to the three alkali-metals to stabilize the first global minima structures containing planar hexacoordinate carbon atoms.</div>

Planar Tetracoordinate Carbons in Allene-Type Structures

“…The chemical bonding analysis revealed a mostly covalent C-E and an electrostatic C-M nature for these ptCs. 39 An extensive search of the potential energy surface of the CE2M2 (E = Si-Pb; M=Li/Na) series in the singlet and triplet state were performed (see the ESI). Table 1 shows the five recurrent lower-lying energy motifs.…”

Trapping an Unusual Pentacoordinate Carbon Atom in a Neutral Trialuminum Complex

“…[2,12,13] Interestingly, planar pentacoordinate carbon atoms are often found in strained molecular clusters and solids, and they have been an active niche for theoretical predictions. [14][15][16][17][18][19][20][21][22][23][24] The search for pentacoordinate C atoms in organic molecules started in 1919 by Staudinger, [25] until, in 1999, the first such species having a strained anthracene backbone was prepared and characterized by X-ray diffraction. [1,3] Subsequently, such hypercoordinate carbon centers have been successfully prepared using ligands with various degrees of rigidity.…”