Transition-metal cluster ions in the gas phase. Oxide chemistry of dimeric and trimeric clusters containing iron and cobalt

Abstract

The oxide chemistry of both dimeric and trimetric transition-metal cluster ions containing iron and cobalt was studied in the gas phase by using Fourier transform mass spectrometry (FTMS). The dimers Fe/sub 2//sup +/, CoFe/sup +/, and Co/sub 2//sup +/ react rapidly with ethylene oxide by sequentially abstracting two oxygen atoms, while the trimers FeCo/sub 2/ and Co/sub 3//sup +/ abstract up to three oxygen atoms from ethylene oxide. The dimers and trimers also react with dioxygen. In addition, the bimetallic carbonyl cations Fe/sub 2/(CO)/sub 4//sup +/, CoFe(CO)/sub 3//sup +/, and Co(CO)/sub 3//sup +/ react rapidly with dioxygen by displacing all the carbonyls forming M'MO/sub 2//sup +/ exclusively. The trimetallic carbonyl cations FeCo/sub 2/(CO)/sub 5//sup +/ and Co/sub 3/(CO)/sub 6//sup +/ react rapidly with dioxygen by displacing up to four carbonyls to generate M'M/sub 2/(O)/sub 2/(CO)/sub n//sup +/ (n = 1-3). These species undergo a subsequent reaction with dioxygen which displaces the remaining carbonyls to generate both M'M/sub 2/O/sub 4//sup +/ and M'M/sub 2/O/sub 3//sup +/. The M'M/sub 2/O/sub 4//sup +/ species subsequently transfers an oxygen atom to dioxygen to generate M'M/sub 2/O/sub 3//sup +/ and presumably O/sub 3/. No fragmentations were observed for collisional activation of the M'MO/sup +/, whilemore » the M'MO/sub 2//sup +/ species yielded M/sup +/ and M'MO/sup +/ in low efficiency, the M'M/sub 2/O/sub 3//sup +/ species yielded M/sup +/ and M'MO/sup +/ in very low efficiency, and the M'MO/sub 2/O/sub 4//sup +/ species yielded M'M/sub 2/O/sub 3//sup +/. Finally, the observed ion-molecule reactions yield D/sup 0/(M'M/sup +/-O) > 119 kcal/mol, 204 kcal/mol 85 kcal/mol D/sup 0/(M'M/sub 2/O/sup +/-O) >85 kcal/mol, D/sup 0/(M'M/sub 2/O/sub 2//sup +/-O) > 85 kcal/mol, and D/sup 0/(M'M/sub 2/O/sub 3//sup +/-O) < 25.5 kcal/mol. 49 references, 1 table.« less