Grignard reagents, X-Mg-R, where X is a halide and R is an organic group, are often utilized for C-C bond formation. The heavier alkaline earth metal ions are sometimes used for similar purposes, but their use is much less common. Gas-phase experiments present a unique path by which to examine the chemistry of labile species: they remove (or at least provide significant control over) solvent effects, they provide access to reactive species which would be otherwise unobservable in the condensed phase, and they allow for the direct testing of computational chemical predictions. In this work, gas-phase analogs of Grignard reagents, [Mg-CH3]+, [Ca-CH3]+, [Sr-CH3]+, [Ba-CH3]+, were produced by electrospray ionization (ESI) and their reactions with neutral species were observed and compared using tandem mass spectrometry (MSn) in a linear ion trap (LIT). Recent modifications to our Thermo LTQ XL LIT allow for the intentional introduction of specific reagent gases into the ion trap. Ions are then isolated in the trap and allowed to react with the introduced neutrals for various times, ranging from 1 ms to 10 s. Density functional theory (DFT) was also used to establish the lowest-energy geometries of the species observed in the study, and also to determine the potential energy surfaces of the observed reactions. Data will be presented on the relative reaction rates of the alkaline earth methides with various neutrals, including water, methanol, dichloromethane, acetone, allyl iodide, and methyl iodide, and on the periodic trends observed in the reaction rates and calculated energetics.

Experimental and computational study of the relative reactivies of Gringnard-like organo-group II ions in the gas-phase

ACS Spring Meeting 2021

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