New Insights into the Reactivity of Mn(II) Coordination Complexes with Dioxygen

As a clearer picture of the oxygen activation processes by manganese(II) co-ordination complexes begins to emerge, we are more likely to understand the biological significance of the Mn-O 2 interaction in various enzymes and to use the activated oxygen molecule for the catalytic oxidation of organic substrates. This Comment describes some of the recent advancements in the area of dioxygen activation by manganese(II) complexes. Details regarding the binding of the O 2 moiety to the metal center and the reaction pathway that is taken during the four electron reduction of the O-O double bond are presented. Particular attention is given to new information on Mn(II) Schiff-base complexes as these results provide strong evidence for a more straightforward and simpler oxygen activation process than previously thought. Also described in this article are examples of unique intermetal oxygen atom transfer reactions that the oxo bridged dimers of Mn Schiff-base complexes undergo with electrophilic metal compounds. This recently discovered reactivity pattern for the oxo bridged complexes likely provides the opportunity to resolve the long-standing controversy regarding the multiple oxidation products that are reported to form upon oxidation of Mn(II) compounds by O 2 .