Synthesis, Molecular Structure, Fluxional Behavior, and Tricarbonyliron Transfer Reactions of (η4-1-Azabuta-1,3-diene)tricarbonyliron Complexes

The (η4-1-azabuta-1,3-diene)tricarbonyliron complexes 10 are easily prepared in high yield by condensation of the corresponding arylamines 7 with the cinnamaldehydes 8 and subsequent ultrasound-promoted complexation of the resulting 1-azabuta-1,3-dienes 9 with nonacarbonyldiiron. The complexes 10 are shown to represent excellent reagents for the transfer of the tricarbonyliron fragment onto cyclohexa-1,3-diene (1a). The structural characterization for the complexes 10 is achieved by IR, 1H-NMR, and 13C-NMR spectroscopy, as well as X-ray crystallography of 10b, 10c, and 10l. Using variable temperature 13C-NMR spectroscopy the fluxionality of the complexes 10a, 10b, 10c, 10e, and 2 is investigated and the activation barrier for the turnstile rotation of the tricarbonyliron fragment is determined. The transfer reaction and the structural factors influencing the transfer of the tricarbonyliron fragment are extensively investigated.