A Mechanistic Study of the Migratory Insertion Reaction: A Computational Chemistry Exercise

An exercise in computational chemistry is presented whereby the student models the mechanism of migratory insertion. In the case of migratory insertion of CO into the Mn–CH 3 bond of [Mn(CH 3 )(CO) 5 ], semiempirical calculations (PM3) are used to evaluate the concerted mechanism of methyl migration, followed by coordination of CO. The three-centered transition state is determined along with the activation energy, calculated to be 131 kJ/mol. The 16-electron intermediate [Mn(C(O)CH 3 )(CO) 4 ] is suggested to display an agostic Mn–H interaction as has been postulated previously. The exercise is appropriate as a take-home assignment in a course on inorganic or organometallic chemistry.