Exploring the Role of Carbonate in the Formation of an Organomanganese Tetramer.

The formation of metal-oxygen clusters is an important chemical transformation in biology and catalysis. For example, the biosynthesis of the oxygen-evolving complex in the enzyme photosystem II is a complicated stepwise process that assembles a catalytically active cluster. Herein we describe the role that carbonato ligands have in the formation of the known tetrameric complex [Mn(CO)(μ-OH)] (1). Complex 1 is synthesized in one step via the treatment of Mn(CO) with excess MeNO·2HO. Alternatively, when anhydrous MeNO is used, an OH-free synthetic intermediate (2) with carbonato ligands is produced. Complex 2 produces carbon dioxide, MeNO·2HO, and 1 when treated with water. Labeling studies reveal that the μ-OH ligands in 1 are derived from the water and possibly the carbonato ligands in 2.