C7H122+: A Prototype Hexacoordinate Carbonium Ion

C(7)H(12)(2+) (1), the prototype hexacoordinate carbonium dication was found to be a viable minimum at the MP2/6-31G** and MP2/cc-pVTZ levels. Structure 1 is a propeller shaped molecule resembling a complex involving a C(2+) with three ethylene molecules resulting in the formation of three two-electron, three-center (2e-3c) bonds. Isomeric structure 2 was found to be 21.8 kcal/mol more stable than structure 1. However, conversion of 1 into 2 through transition structure 3 has a barrier of 5.7 kcal/mol. Related structures 4, 5, and 8 were also located as minima for C(7)H(12)(2+). The isoelectronic boron analogue BC(6)H(12)(+) (10) was also computed to be a minimum at the same level of calculations.