Unimolecular dissociation of anions derived from maleic acid (MaH(2)) in the gas phase: MaH(-) and MaMgCl(-)-relationship to Grignard chemistry and reductive CO2 fixation

摘要

We have conducted collision-induced dissociation experiments on the hydrogen maleate anion (MaH(-), m/z = 115) and the anionic maleate-MgCl complex (MaMgCl(-), m/z = 173). In addition, we have computationally investigated the observed fragmentation reactions. We find that both anions readily undergo two consecutive decarboxylations resulting in product ions at m/z = 71 and m/z 27 for MaH(-), and at m/z = 129 and m/z 85 for MaMgCl(-). The first decarboxylation is more facile for MaMgCl(-) than for MaH-, while loss of CO2 from Ma(-CO2) H-is more facile than that for Ma(-CO2)MgCl-. We also find that MaH-loses water, and we propose a mechanism for this loss. No first-generation fragmentation product other than Ma(-CO2) MgCl- is seen for MaMgCl-. Based on the observed unimolecular chemistry, we discuss some of its implications on reductive CO2-fixation and Grignard chemistry.