Planar hexacoordinate carbon: A viable possibility

The viability of molecules with planar hexacoordinate carbon atoms is demon strated by density-functional theory (DFT) calculations for CB62-, a CB6H2 isomer, and three C3B4 minima. All of these species have six pi electrons a nd are aromatic. Although other C3B4 isomers are lower in energy, the activ ation barriers for the rearrangements of the three planar carbon C3B4 minim a into more stable isomers are appreciable, and experimental observation sh ould be possible. High-Level ab initio calculations confirm the DFT results . The planar hexacoordination in these species does not violate the octet r ule because six partial bonds to the central carbons are involved.