Ferrocene‐Fused Acenequinones: Synthesis, Structure and Reaction Chemistry

Abstract

AbstractThe synthesis of anti‐[1.1](2,17)(6,13)ferrocenophane‐1,12‐dione (2) is discussed. By addition of LiAlH4, NaBH4 or Wittig's reagent only one keto group reacted to give HO‐ or cC3H4‐functionalized [1.1](2,17)(6,13)ferrocenophan‐12‐hydroxy‐1‐one (3) and [1.1](2,17)(6,13)ferrocenophan‐12‐cyclopropane‐1‐one (4). Exchange of CO by CS groups is possible upon addition of Lawesson's reagent to 2 forming [1.1](2,17)(6,13)ferrocenophan‐1,12‐dithioketone (5). Theoretical studies confirm the different reactivities of the CO groups. Electrochemical studies on 2–5 showed separated reversible one‐electron events for 2–4 (125–925 mV) and an irreversible one for 5. The ferrocenyls in 4 are easier to oxidize, due to their higher electron‐richness. In 2 a larger redox separation comes about suggesting a stronger intermetallic interaction between FeII/FeIII in the mixed‐valent species. In situ UV‐vis/NIR studies confirm that 2 is a weak coupled class II system according to the classification of Robin and Day. Compounds 3 and 4 display electrostatic interactions among the ferrocenyls as oxidation progresses.