η5-6-N-dimethylamino-2,3-benzofulvenchromium tricarbonyl

η 5 -6- N -Dimethylamino-2,3-benzofulvenchromium tricarbonyl has been synthesized. The rotational isomerism of the complex and the parent fulvene and the kinetic parameters of the barriers to rotation about the bond have been determined by dynamic 1 H NMR spectroscopy. π-Coordination increases the free energy of the rotational barrier, i.e. increases the degree of double-bond character between the C(6) and N atoms and, hence, enhances the π-electron polarization of the exocyclic double bond. Electron impact mass spectra of the complex and the parent fulvene have been investigated.