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

[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 (λmax = 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.