TIME-RESOLVED INFRARED STUDIES OF GAS-PHASE COORDINATIVELY UNSATURATED PHOTOFRAGMENTS (ETA-5-C5H5)MN(CO)X (X = 2 AND 1)

Time-resolved infrared spectroscopy is used to study the coordinatively unsaturated species eta-5-C5H5)Mn(CO)x (x = 2 and 1) generated by 266- and 355-nm laser photolysis of (eta-5-C5H5)Mn(CO)3 in the gas phase. (eta-5-C5H5)Mn(CO) is the predominant photoproduct upon 266-nm photolysis while both (eta-5-C5H5)Mn(CO) and (eta-5-C3H5)Mn(CO)2 am produced upon 355-nm photolysis. IR spectra in the region of 1820-2033 cm-1 are assigned for the coordinatively unsaturated species (eta-5-C5H5)Mn(CO)x and found to be in major disagreement with those obtained in condensed phases. The rate constants for the reactions of (eta-5-C5H5)Mn(CO)2 and (eta-5-C5H5)Mn(CO) with CO are determined to be (5.9 +/- 0.4) x 10(11) and (6.7 +/- 0.2) x 10(12) cm3 mol-1 s-1, respectively. The rate constant for the reaction of (eta-5-C5H5)Mn(CO) with CO is on the order of 1/10 gas kinetic while the corresponding value for (eta-5-C5H5)Mn(CO)2 is over an order of magnitude smaller. The magnitudes of the rate constants for the reactions of (eta-5-C5H5)Mn(CO)x with CO are compared with those of (eta-6-C6H6)Cr(CO)x previously observed and are discussed in terms of the change of spin states of these reactions. In addition, it is found that the presence of care gas Q (Q = Ar, He, and Xe) has remarkable influence on the kinetic behavior of (eta-5-C5H5)Mn(CO)2, implying the formation of rare-gas complexes (eta-5-C5H5)Mn(CO)2.Q in the gas phase.