Experimental and theoretical study of the metallotropic migrations in cyclooctatetraeneosmiumtricarbonyl

Experimental verification of the mechanism of metallotropic migrations in cyclooctatetraeneosmiumtricarbonyl (3) by means of 2D EXSY NMR spectroscopy confirmed the mechanism of [1,2]-Os shifts with low activation barrier (E(A) = 5.9 +/- 0.2 kcal mol(-1), ln A = 32 +/- 1). Transition-state structure for this rearrangement obtained at the B3LYP/SDD level of theory testifies for the activation energy of 6.5 kcal mol(-1) and supports well the selective [1,2]-Os shifts observed for 3.