Question

Mn(salen)(AcAc) was actually a failed experiment by design. You were not supposed to synthesize this compound. You should remember that Mn(salpn)(AcAc) was readily synthesized in week 3 as crystalline materials. In your discussion section, explain why we cannot make Mn(salen)(AcAc)? (hint: salpn has a 3-carbon chain between two nitrogen donors, which make it more flexible).

Answer 1

Mn(salen)(AcAC) complex design consists of a ethylene bridge between the salicyladehyde groups, so there exist a steric problem and also the restriction in rotation of the bulky groupmakes it difficult for the incoming acetylaetonate group to coordinate with the metal centre whereas in case of Mn(salpn) you find a three carbon chain between the nitrogen atoms which will provide the required flexibility to rearrange in a position to bind with the incoming acetyacetonate group.