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arene ligands; coordination modes; electrochemistry; iron; sandwich complexes
Abstract:
Reaction of [(η5‐Me4EtC5)FeIICl(tmeda)] (tmeda=N,N,N′N′‐tetramethylethylenediamine) with a polyanion solution of decacyclene (1) results in the formation of the triple‐deckers [{(η5‐Me4EtC5)Fe}2‐μ2‐(η6:η6‐decacyclene)] (3) and [{(η5‐Me4EtC5)Fe}4‐μ4‐(η6:η6:η6:η6‐decacyclene)] (4). Metal complexation in 3 and 4 occurs on opposite faces of the π perimeter in an alternating mode. The decacyclene ring adopts a gently twisted molecular propeller geometry with twofold crystallographic symmetry (C2). Complex 4 crystallizes in the chiral space group C2221; the investigated crystal only contains decacyclene rings with M chirality. The handedness can be assigned unambiguously to the presence of the iron atoms. Cyclovoltammetric studies revealed quasireversible behavior of the redox events and a strong interaction of the Fe atoms in 3 and 4, exemplified by potential differences ΔE of 660 and 770(780) mV between the first and the second individual oxidation processes. This corresponds to a high degree of metal–metal interaction for 3 and 4. The sucesssful syntheses of 3 and 4 together with earlier results from our laboratory proves that all five‐ and six‐membered π subunit sets of 1 are prone to metal complexation. A clear site preference in 1 towards the complexation of [CpR]iron, ‐cobalt, and ‐nickel fragments exists.
