Reactions of Atomic Metal Anions in the Gas phase: Competition between Electron Transfer, Proton Abstraction and Bond Activation
journal contributionposted on 08.12.2011, 00:00 by Sharon Curtis, Jason DiMuzio, Alex Mungham, Julie Roy, Dhiya Hassan, Justin Renaud, Paul M. Mayer
Bare metal anions K–, Rb–, Cs–, Fe–, Co–, Ni–, Cu–, and Ag–, generated by electrospray ionization of the corresponding oxalate or tricarballylate solutions, were allowed to react with methyl and ethyl chloride, methyl bromide, nitromethane, and acetonitrile in the collision hexapole of a triple-quadrupole mass spectrometer. Observed reactions include (a) the formation of halide, nitride, and cyanide anions, which was shown to be likely due to the insertion of the metal into the C–X, C–N, and C–C bonds, (b) transfer of H+ from the organic molecule, which is demonstrated to most likely be due to the simple transfer of a proton to form neutral metal hydride, and (c) in the case of nitromethane, direct electron transfer to form the nitromethane radical anion. Interestingly, Co– was the only metal anion to transfer an electron to acetonitrile. Differences in the reactions are related to the differences in electron affinity of the metals and the ΔacidH° of the metals and organic substrates. Density functional theory calculations at the B3-LYP/6-311++G(3df,2p)//B3-LYP/6-31+G(d) level of theory shed light on the relative energetics of these processes and the mechanisms by which they take place.