RARE-GAS METAL-CARBONYL-COMPLEXES - BONDING OF RARE-GAS ATOMS TO THE GROUP-VI PENTACARBONYLS

Transient infrared spectroscopy has been used to study reactions of M(CO)5 generated by 355-nm photolysis of M(CO)6 where M = Cr, Mo, and W. At 298 K, M(CO)5 reacts with CO with bimolecular rate constants of (1.4 +/- 0.2) X 10(-10), (1.5 +/- 0.1) X 10(-10), and (1.4 +/- 0.1) X 10(-10) cm3 molecule-1 s-1 for Cr, Mo, and W, respectively. M(CO)5 also reacts with Xe with bimolecular rate constants of (0.9 +/- 0.4) X 10(-10), (0.9 +/- 0.4) X 10(-10), and (2.6 +/- 0.2) X 10(-10) cm3 molecule-1 s-1 for Cr, Mo, and W, respectively. Infrared absorptions attributed to M(CO)5Xe and W(CO)5Kr were observed. The rate of dissociative loss of the Xe atom from the M(CO)5Xe complexes was determined by the observation of the rate of regeneration of M(CO)6 in a reaction mixture consisting of M(CO)5, CO, and Xe. The bond dissociation energy for the loss of the Xe atom from M(CO)5Xe for all three metals is the same within experimental error and has an average value of 8.5 kcal/mol. A bond dissociation energy was estimated for the loss of Kr from W(CO)5Kr, and an upper limit can be estimated for the bond dissociation energy for loss of Ar from W(CO)5Ar.