Planar hexacoordinate carbon

Planar hexacoordinate carbon in chemistry describes a molecular geometry featuring a planar arrangement of carbon with six surrounding atoms. No actual chemical compounds having this particular hexacoordinate configuration have been reported but quantum mechanical methods have demonstrated that these molecules are a possibility.^[1][2][3] Examples of molecules investigated with computational methods are the B₆C dianion,^[2][4] the CN₃Be₃⁺ ion, the CO₃Li₃⁺ ion^[5] and the CN₃Mg₃⁺ ion.^[6] A simulated Be₂C monolayer is reported to consist of quasi-planar hexacoordinate carbon atoms.^[7]

Planar hexacoordinate carbon

On the other hand, experimental research has confirmed that the pentagonal-pyramidal hexamethylbenzene ion, C₆(CH₃)₆²⁺, contains a hexacoordinate carbon atom.^[8] Furthermore, a heptacoordinate carbon atom has been predicted to be involved in a stable hexagonal-pyramidal configuration of tropylium trication, (C₇H₇)³⁺.^[9]