Gas phase models of hydride transfer from divalent alkaline earth metals to CO and CHO.

The reactivity of HMg, HMgCl, and HMgCl in hydride transfer reactions with CO and CHO were studied by means of the reverse reactions-decarboxylation of HCOMgCl and deformylation of CHOMgCl ( = 0-2)-by a combination of quantum chemical computations and mass spectrometry experiments. HCOMg, HCOMgCl and HCOMgCl display similar energetics for unimolecular carbon dioxide loss; for CHOMg, CHOMgCl and CHOMgCl, formaldehyde loss is more favourable for the cationic species than for the anionic one, with the neutral species found in-between. Despite very similar overall thermochemistry for each of the charge states of the CO and CHO systems, the intermediate reaction barriers are higher for the CO eliminations due to a more complex and demanding reaction mechanism.