Planar tetracoordinate carbons in cyclic semisaturated hydrocarbons

The [C.sub.5.sup.2-] skeleton in combination with saturated hydrocarbon fragments is used to obtain a series of planar tetracoordinate carbon molecules in cyclic semisaturated hydrocarbons. The system is the first example of semisaturated cycles containing a planar tetracoordinate carbon stabilized only by electronic factors.