1,1′-Diethyl-2,2′,3,3′,4,4′,5,5′-octamethylferrocenium tetracyanoethylenide, [Fe(C5EtMe4)2]+[TCNE]−, a charge-transfer salt magnetic solid with a novel structural motif

1,1′-Diethyl-2,2′,3,3′,4,4′,5,5′-octamethylferrocene has been utilized as a one-electron donor in the synthesis of a tetracyanoethylene charge-transfer salt, [Fe(C5EtMe4)2]+[TCNE]−. Structural characterization shows that it adopts an arrangement of anions and cations completely different from the usual π stacking seen in analogous decamethylferrocenium compounds. The TCNE radical sits along side of the ferrocene, nearly perpendicular to the planes of the C5 rings. The nearly square geometry of the TCNE anion creates disorder over two orientations. [Fe(C5EtMe4)2]+[TCNE]− is a simple paramagnet exhibiting neither long-range magnetic order nor slow paramagnetic relaxation to the lowest measured temperatures (ca. 1.8 K) as determined by both ac and dc magnetic susceptibility and Mössbauer spectroscopy (ca. 1.3 K).