Unexpected C–C Bond Formation with a Ferrocenyl Fischer Carbene Complex

Thermolysis of (OC) 5 Cr(C(OEt)(Fc)) ( 1 ) gives 2, N ‐diferrocenyl acetamide Fc–CH 2 –CO–NH–Fc ( 2 ) in the presence of amino ferrocene Fc‐NH 2 . In the absence of a nucleophile, 4‐ethoxy‐2,3,4‐triferrocenyl‐cyclobut‐2‐enone ( 3 ) forms from 1 under thermal activation. Single crystal X‐ray diffraction, NMR spectroscopy and mass spectrometry unambiguously confirm the structure of both unexpected products. Quantum chemical calculations and...