Life Depends on Metal Oxos

Harry B. Gray

California Institute of Technology

The dianionic oxo ligand occupies a very special place in coordination chemistry, owing to its ability to donate pi electrons to stabilize high oxidation states of metals. The ligand field theory of multiple bonding in metal oxos predicts that there must be an oxo wall between Fe-Ru-Os and Co-Rh-Ir in the periodic table. Iron and manganese oxos, which are on the allowed side of the wall, play key roles in three of the most important chemical reactions on planet Earth: water oxidation to oxygen; oxygen reduction to water; and hydrocarbon oxygenation to alcohols.