Metal-oxos in chemistry and biology

Abstract

The dianionic oxo ligand occupies a very special place in coordination chem., owing to its ability to donate pi electrons to stabilize high oxidn. states of metals. My papers on the ligand field theory of multiple bonding in metal-oxos were published over 50 years ago in the first vol. of Inorg. Chem. The theory, which accounts for the optical and EPR spectroscopic properties of these complexes, also predicts that there must be an "oxo wall" between Fe-Ru-Os and Co-Rh-Ir in the periodic table. There have been many attempts to break down the wall, but it is still in pretty good shape!. I will review this early work, then discuss the roles metal-oxos play in two of the most important chem. reactions on planet Earth, hydrocarbon oxygenation catalyzed by cytochrome P 450, and solar-driven water oxidn. catalyzed by the Mn-Ca cluster of photosystem-II. Water splitting catalyzed by inorg. materials also is of great current interest. In this area, recent work in my lab has shown that high-valent iron-oxos likely are key intermediates in water oxidn. catalyzed by robust Fe,Ni-layered double hydroxides.