When methyl manganese pentacarbonyl is treated with carbon monoxide in e.g. di-n-butyl ether, acetyl manganese pentacarbonyl is formed. This classic experiment conducted by Cotton (of quadruple bond fame) and Calderazzo in 1962 dates from an era when chemists conducted extensive kinetic analyses to back up any mechanistic speculations. Their suggested transition state is outlined below. Here I subject their speculations to a quantum mechanical “reality check“.
- F. Calderazzo, and F.A. Cotton, "Carbon Monoxide Insertion Reactions. I. The Carbonylation of Methyl Manganese Pentacarbonyl and Decarbonylation of Acetyl Manganese Pentacarbonyl", Inorganic Chemistry, vol. 1, pp. 30-36, 1962. http://dx.doi.org/10.1021/ic50001a008