The Missing Link in Ferrocenophane Chemistry: Isolation of a Carba[1]Ferrocenophane

ABSTRACT [1]Ferrocenophanes, which are single‐atom bridged ansa ‐ferrocenes, have gained significant interest as monomers for ring‐opening polymerization (ROP) reactions for the preparation of main‐chain ferrocene‐based metallopolymers. While all conceivable third and fourth row p ‐block elements are known as bridging atoms, boron remained the only second row p ‐block element to be incorporated into [1]ferrocenophanes, so far. Here, we describe the synthesis, isolation and full characterization of a carba[1]ferrocenophane, previously speculated to be unstable due to its high energy conformation. Single‐crystal X‐ray diffraction reveals the highest angular deflection from ferrocene's coplanarity so far ( α = 36.7°, δ = 151.8°), which is reflected by its deep red color ( λ max = 511 nm) and high air‐sensitivity. Nonetheless, the carba[1]ferrocenophane is thermally robust up to 200°C, which, according to DFT calculations, is due to non‐covalent interactions arising from the ligand system.