Investigation of rotational isomerization of 6-dimethylaminofulventricarbonyl-chromium, -molybdenum and -tungsten by dynamic 1H NMR spectroscopy

1 H NMR spectroscopy was used in studying the rotational isomerism of 6-dimethylaminofulvene and its complexes with carbonyls of chromium, molybdenum and tungsten. The energy parameters for the barriers to rotation about the c(6)N bond were determined. It is shown that the coordination of 6-dimethylaminofulvene with Group VIB metal carbonyls increases the free energy for the barrier to rotation about the C(6)N bond, that is, it increases the degree of double-bond character between the C(6) and N atoms. The free energy for the rotational barriers, and hence, the degree of double-bond character, are strongly dependent on the nature of the central metal atom, increasing in the sequence W