Fortuitous Ion–Molecule Reaction Enables Enumeration of Metal–Hydrogen Bonds Present in Gaseous Ions

Abstract

Upon mass selection and ion activation under mass spectrometric conditions, gaseous formate adducts of many metal formates undergo decarboxylation and form product ions that bear metal–hydrogen bonds. Fortuitously, we noted that negative-ion spectra of several such formate adducts showed many peaks that could not be rationalized by the conventional fragmentation pathways attributed to the precursor ion. Subsequent experimentation proved that these enigmatic peaks are due to an ion–molecule reaction that takes place between traces of adventitious water vapor in the collision gas and the in situ formed product anions bearing metal–hydrogen bonds, generated by the fragmentation of the formate adducts. Results show that metal–hydrogen bonds of the group 2 elements are particularly susceptible to this reaction. For example, in the product-ion spectrum of [Sr( η 2 - O 2 CH) 3 ] − , the peak at m / z 91 for SrH 3 – was accompanied by three peaks at higher m / z ratios. These peaks, at m / z 107, 123, and 139, represented SrH 2 (OH) 1 – , SrH 1 (OH) 2 – , and Sr(OH) 3 – , respectively. These satellite peaks, which were separated by 16 m / z units, were attributed to adducts formed due to the high affinity of gas-phase anions bearing metal–hydrogen bonds to water. Although undesired, these peaks are diagnostically useful to determine the number of metal–hydrogen bonds present in a precursor ion. Even though the peaks were less pronounced, analogous reactions were noted from the adducts of the group 1 elements as well. Moreover, Gibbs free energy values computed for the interaction of [H-Mg(η 2 -O 2 CH) 2 ] − with water to form [HO-Mg(η 2 -OCOH) 2 ] − and H 2 indicated that this is an exergonic reaction.

Formation of Protonated ortho-Quinonimide from ortho-Iodoaniline in the Gas Phase by a Molecular-Oxygen-Mediated, ortho-Isomer-Specific Fragmentation Mechanism

“…Reactions between gaseous ions and neutral molecules have been investigated from the early stages of mass spectrometry. − Many examples have been documented of adventitious or deliberate ion–molecule reactions (IMR) that occur between residual neutral gas molecules and nontargeted or mass-selected ions. − Such ion–molecule reactions are often useful as probes for molecular structure and functional group determinations. − Some of these reactions have been particularly useful for the differentiation of isomeric radical ions. − Ion–molecule reactions are usually investigated using ion-storing mass analyzers such as ion traps and Fourier-transform ion cyclotron resonance instruments . Occasionally, the formation of ion–molecule reaction adducts have also been observed on tandem-in-space instruments as well. ,, …”

Gas phase models of hydride transfer from divalent alkaline earth metals to CO2 and CH2O

“…It should also be mentioned that more recently, Attygalle and co-workers, using a similar technique, reported the formation of a plethora of metal hydride anions, including AlH 4 À . 16 In this work, we aim to increase our understanding of the reactions of HMgX species (X = halide) with carbonyl compounds, in particular carbon dioxide and formaldehyde. For practical reasons, the reactions studied will be the reverse of the hydride transfer, i.e., the decarboxylation and deformylation of HCO 2 MgX n +/0/À and CH 3 OMgX n +/0/À , respectively (n = 0-2).…”