Systematic Ligand Effects in the Reactions of Fe+(D-6) and FeX+((5)Delta) with CF3X (X = Cl, Br, I). Ion Mobility Measurements of FeX+((5)Delta) (X = F, Cl, Br, I) in He

作者：Taylor William S^*; Pedder Randall E; Eden Angela B; Emmerling Christopher L

来源：Journal of Physical Chemistry A, 2018, 122(32): 6509-6523.

DOI：10.1021/acs.jpca.8b05708

The gas phase reactions of Fe+(D-6) and FeX+((5)Delta) with CF3X (X = Cl, Br, I) were examined using a selected -ion drift cell reactor under near thermal energetic conditions. All reactions were carried out in a uniform electric field at a total pressure of 3.5 Torr at room temperature. In addition, reduced zero -field mobilities were measured for FeX+((5)Delta) (X = F, Cl, Br, I) in He, yielding values of 14.2 +/- 0.4, 13.7 +/- 0.3, 13.3 +/- 0.2, and 13.0 +/- 0.3 cm(2).V-1.s(-1), respectively. Fe+(D-6) reacts slowly with (CFCl)-Cl-3 and CF3Br, producing an adduct exclusively with the former and FeBr+ with the latter. Conversely, Fe+(D-6) exhibits efficient chemistry with CF3I to yield Fer, FeCF3+, and FeFI+ in parallel reactions. Dependent on the halogen, FeX+((5)Delta) reactions display one or more of four different processes: F- abstraction, X- abstraction, halogen switching, and association. In general, the presence of the halogen ligand enhances the rate of reaction over that of Fe+(D-6) with the same molecular substrate. With CF3Cl, this ligand effect is observed to vary systematically with the electron-withdrawing capability of the halogen. This is illustrated by the correlation between reaction efficiency and the charge distribution on FeX+((5)Delta) as determined from DFT calculations. Specific reaction outcomes for the FeX+((5)Delta) reactions lead to upper and lower bounds on XFe-Y bond strengths (X, Y = F, Cl, Br, I) that are generally consistent with one another and with known trends.

• 出版日期2018-8-16