N,N,2,4,6-PENTAMETHYLANILINETRICARBONYLCHROMIUM(0) - AN INTERESTING CASE OF RESTRICTED ROTATION IN THE ARENETRICARBONYLCHROMIUM SERIES

Restricted rotation of the dialkylamino groups in N,N,2,4,6-pentamethy lanilinetricarbonylchromium(0) (1) and ethyl-2,4,6-trimethylanilinetri carbonylchromium(0) (2) has been investigated using variable temperatu re H-1 and C-13 NMR. Below 266 K the H-1 NMR spectrum of 1 shows a sha rp doublet for the signal of the NMe(2) group which gradually broadens as the temperature is increased. Above room temperature the signal wi dth decreases, becoming a sharp singlet at > 310 K. Analogous changes are seen for the NEt(2) group in 2. The barrier to rotation of the NMe , group in 1 was found to be 13.7 kcal mol(-1).