METAL-CARBONYL-COMPLEXES WITH XENON AND KRYPTON - IR-SPECTRA, CO SUBSTITUTION KINETICS, AND BOND-ENERGIES

IR spectra for complexes between Xe and Kr and M(CO)5 (M = Cr, W) have been obtained using laser photolysis of M(CO)6 and rapid-scan FTIR spectroscopy of liquid rare-gas solutions. The Kr complexes have lifetimes of approximately 0.1 s at 150 K in liquid Kr while W(CO)5Xe has a lifetime of approximately 1.5 min at 170.0 K in liquid Xe. W(CO)5Xe reacts with CO to form W(CO)6 and the CO substitution kinetics were investigated in liquid Xe over a range of temperatures (173.0-198.0 K) and CO concentrations. The kinetics are consistent with a dissociative substitution mechanism in which W(CO)5Xe is in equilibrium with W(CO)5. From the temperature dependence of the equilibrium constant, the Xe-W bond energy in W(CO)5Xe is obtained, DELTAH = 8.4 +/- 0.2 kcal/mol in good agreement with a recent gas-phase value.