Laser flash photolysis, EPR and Raman studies of liquids at elevated pressures

A laser flash photolysis kinetic study of a W(CO)(sub 5) intermediate reacting with several different substituted 2,2(prime)-bipyridine ligands at pressures up to 150 MPa in liquid toluene has confirmed the considerable influence of steric hindrance on the mechanism of a thermal ring closure reaction. A similar laser flash photolysis kinetic study has been carried out with Mo(CO)(sub 6) and several bidentate ligands resembling 2,2(prime)-bipyridine dissolved in supercritical carbon dioxide. A much larger negative activation volume is found in supercritical carbon dioxide than observed previously with this solute system dissolved in liquid toluene. Rate of replacement of one polydentate ligand by another stronger chelating agent in the first coordination sphere of aqueous gadolinium(III) ion was measured over a range of pressures and other variables using a stopped-flow spectrophotometer. Two consecutive first order reaction steps are observed that show acid-catalysis.