COORDINATION OF MOLECULAR NITROGEN AND HYDROGEN TO (ETA-6-C6H6)CR(CO)X AND (ETA-5-C5H5)MN(CO)X (X = 2 AND 1) IN THE GAS-PHASE

Time-resolved infrared absorption spectroscopy is used to study the coordination reactions of N2 and H-2 with photolytically generated coordinatively unsaturated species (eta6-C6H6)Cr(CO)x and (eta5-C5H5)Mn(CO)x (x = 2 and 1) in the gas phase. Additions of N2 and H-2 to (eta6-C6H6)Cr(CO)2 and (eta5-C5H5)Mn(CO)2 form corresponding molecular nitrogen and hydrogen complexes. Additions of N2 and H-2 to (eta6-C6H6)Cr(CO) are confirmed although no product absorption is observed. By comparison, reactions of N2 and H-2 with (eta5-C5H5)Mn(CO) are not observed, presumably due to spectral overlap. The rate constants for reactions of N2 and H-2 With (eta6-C6H6)Cr(CO)2 and (eta5-C5H5)Mn(CO)2 as well as with (eta6-C6H6)Cr(CO) are measured, and an upper limit for the rate constants for reactions of N2 and H-2 with (eta5-C5H5)Mn(CO) is estimated. Significant differences are observed for the rate constants for reactions of different species and discussed with respect to spin-allowed versus disallowed processes.