MECHANISM OF CHELATION OF PHENANTHROLINE DERIVATIVES TO MO(CO)(5) DEDUCED FROM PULSED PHOTOLYSIS STUDIES IN SEVERAL SOLVENTS AT HIGH-PRESSURE

A laser flash-photolysis kinetic study has been carried out an the con centration, temperature and pressure dependence of chelation reactions of the type [Mo(CO)(5)(L-L)] --> [Mo(CO)(4)(L-L)] + CO, where L-L rep resents 1,10-phenanthroline (phen) and a series of substituted phen li gands in several solvents. The activation parameters for these thermal ring-closure reactions are sensitive to the nature of the solvent, as well as to electronic and steric effects arising from the phen ligand . All the observed kinetic effects can be accounted for by an intercha nge ligand-substitution mechanism during which CO is displaced by the chelate.