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Zusammenfassung:
An extended version of the CNDO formalism is used to study the mechanism of the CO insertion as an example of intra-molecular insertion reactions which take place in the ligand sphere of a transition metal atom. It is shown that charge density and bond order arguments can explain the experimental facts on a whole class of compounds: Mn(CO)5R with R = H, CH3, C2H5, CHO, CH2F, CF3. The mechanism is predicted to be an R migration. The sequence of the reaction rates is correctly given, and especially the strong inhibition of the reaction by increasing fluorination of the substituent. The reversibility of the reaction is also considered. In the case of Mn(CO)5C2H5 a possible side reaction by abstraction of β-hydrogen instead of alkyl migration is expected, and actually found experimentally.
