The redox pair {(μ4-TCNE)[Fe(CO)2(C5H5)]4}4+/3+: Surprisingly small metal–ligand interaction and the first resolved EPR hyperfine structure (13C, 14N, 57Fe) of a tetranuclear complex with TCNEradical dot−

Electrochemistry and absorption spectroscopy (UV/Vis, IR) of the complex {(μ4-TCNE)[Fe(CO)2(C5H5)]4}(BF4)4 reveal only a small degree of metal-to-ligand π back donation, in contrast to previously characterized compounds [(TCNE)(MLn)4]. Accordingly, the one-electron reduced {(μ4-TCNE)[Fe(CO)2(C5H5)]4}3+ exhibits a very well resolved EPR spectrum at g = 1.9965 with detectable coupling of 0.055 mT for 57Fe in natural abundance from four coordinated [Fe(CO)2(C5H5)]+ groups.