Direct evidence of adsorption induced Cr-II mobility on the SiO2 surface upon complexation by CO

In situ, temperature dependent, XAFS proved that Cr-II grafted on SiO2 is extracted from the surface upon CO adsorption at 100 K: Delta RCr-O = +0.08 angstrom. CO adsorption evolves into two coverage dependent steps: (i) displacement of weak siloxane ligands (non-classical carbonyls); (ii) relaxation of RCr-O surface bond, RCr-CO optimization and transformation into classical carbonyls.