CO₂‐Aktivierung an Übergangsmetallzentren: Simulation enzymatischer CO₂‐Fixierungs‐ und Transferreaktionen durch elektronenreiche (Diazadien)magnesium‐ und ‐mangan‐Komplexe

Activation of CO 2 at Transition‐Metal Centres: Simulation of Enzymatic CO 2 Fixation and Transfer Reactions by Electron‐Rich (Diazadiene)magnesium and ‐manganese Complexes Electron‐rich diazadiene complexes of Mg and Mn can be used as model compounds for enzymatic carboxylation reactions e.g. the „dark reaction”︁ of the photosynthesis or in biotinedependent CO 2 conversion reactions. The activity of the complexes to fix and transfer carbon dioxide strongly depends on the nature of the metal (Mg and Mn are active central atoms, other transition metals are inactive), the π aciditiy of the chelate ligand, and the structure of the complexes. The dimeric manganese complex IIa , the structure of which could be determined by X‐ray structure analysis, is one of the most active compounds. NMR studies reveal that the CO 2 transfer to substrates with active C—H bonds takes place in the coordination sphere of the metal atom. Carrier of activated CO 2 is the N—COO group.