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).