The Effects of Redox-Inactive Metal Ions on the Activation of Dioxygen: Isolation and Characterization of a Heterobimetallic Complex Containing a MnIII–(μ-OH)–CaII Core

Rate enhancements for the reduction of dioxygen by a MnII complex were observed in the presence of redox-inactive group 2 metal ions. The rate changes were correlated with an increase in the Lewis acidity of the group 2 metal ions. These studies led to the isolation of heterobimetallic complexes containing MnIII–(μ-OH)–MII cores (MII = CaII, BaII) in which the hydroxo oxygen atom is derived from O2. This type of core structure has relevance to the oxygen-evolving complex within photosystem II.