The potassium salt of cyclooctatetraene dianion is easily made by reaction of potassium and cyclooctatetraene. The dianion is cyclic, planar, each C atom is sp2 hybridized and there are 10 pi-electrons. This dianion is aromatic according to the (4N+2) Hueckel rule with N=2. Note that this dianion stays planar even though the planar structure forces the C-C-C angls to be 135 degrees!