Gas‐phase fragmentation of metal adducts of alkali‐metal oxalate salts

Upon collisional activation, gaseous metal adducts of lithium, sodium and potassium oxalate salts undergo an expulsion of CO 2 , followed by an ejection of CO to generate a product ion that retains all three metals atoms of the precursor. Spectra recorded even at very low collision energies (2 eV) showed peaks for a 44‐Da neutral fragment loss. Density functional theory calculations predicted that the ejection of CO 2 requires less energy than an expulsion of a Na + and that the [Na 3 CO 2 ] + product ion formed in this way bears a planar geometry. Furthermore, spectra of [Na 3 C 2 O 4 ] + and [ 39 K 3 C 2 O 4 ] + recorded at higher collision energies showed additional peaks at m/z 90 and m/z 122 for the radical cations [Na 2 CO 2 ] +• and [K 2 CO 2 ] +• , respectively, which represented a loss of an M • from the precursor ions. Moreover, [Na 3 CO 2 ] + , [ 39 K 3 CO 2 ] + and [Li 3 CO 2 ] + ions also undergo a CO loss to form [M 3 O] + . Furthermore, product‐ion spectra for [Na 3 C 2 O 4 ] + and [ 39 K 3 C 2 O 4 ] + recorded at low collision energies showed an unexpected peak at m/z 63 for [Na 2 OH] + and m/z 95 for [ 39 K 2 OH] + , respectively. An additional peak observed at m/z 65 for [Na 2 18 OH] + in the spectrum recorded for [Na 3 C 2 O 4 ] + , after the addition of some H 2 18 O to the collision gas, confirmed that the [Na 2 OH] + ion is formed by an ion–molecule reaction with residual water in the collision cell. Copyright © 2014 John Wiley & Sons, Ltd.