[Et 4 N] 2 [TCNE] 2 (TCNE = tetracyanoethylene) – an example of an exceptionally long 2.827 Å CC bond

The reaction of [Et4N]I and tetracyanoethylene (TCNE) forms [Et4N]2[TCNE]2, which possesses [TCNE]22− with a 2.827(3) Å intradimer CC bond distance and exhibits νCN at 2191, 2170 and 2163 cm−1, νCC at 1365 cm−1, and UV-Vis bands at 26 150 and 16 850 cm−1.