IntroductionInterest in organic compounds exhibiting unusually long CC bonds has been the subject of several recent studies.1–3The longest sp3–sp3C–C single bond reported to date is 1.73 Å,1,2whereas several [TCNE]22−(TCNE = tetracyanoethylene) dimers have been recently reported to form cation-assisted, long, two-electron π*–π* CC bonds involving four carbon atoms. These CC bonds range from 2.833 to 3.09 Å. The cations range from electrostatically bonded Tl+ 4and K+ 5to large, bulky, non­coordinating cations such as [Cr(C6H6)2]+,6[Fe(C5H4)2C3H6]+,7and [TDAE]2+[TDAE = (Me2N)2CC(NMe2)2].4,8Herein we report the structure, IR and UV­Vis spectroscopic properties of [Et4N]2[TCNE]2, a new example of the [TCNE]22−dimer, which exhibits the shortest π*–π* CC bond for this family of compounds.