The reaction of Lnl(3) . xMeCN (Ln = Gd, Dy) and TCNE (tetracyanoethylene) in acetonitrile forms Ln(2)[C-4(CN)(8)](3).xMeCN. These paramagnetic light-colored solids contain the S = 0 octacyanobutandiide dianion, [C4(CN)(8)](2-), which upon desolvation of these products forms dark green Ln(TCNE)(3), In these compounds the central C-C sigma bond in [C-4(CN)(8)](2-) is broken, re-forming S = 1/2 [TCNE](.-) as evidenced by the color change and the infrared spectra. Ln(TCNE)(3) exhibit coupling between Ln(3+) and [TCNE](.-) and magnetically order as ferrimagnets at 8.5 (Dy) and 3.5 (Gd) K.