Ion molecule reactions of Mg+(H2O)(n), n approximate to 20-60, with O-2 and CO2 are studied by Fourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry. O-2 and CO2 are taken up by the clusters. Both reactions correspond to the chemistry of hydrated electrons (H2O)(n)(-). Density functional theory calculations predicted that the solvation structures of Mg+(H2O)(16) contain a hydrated electron that is solvated remotely from a hexa-coordinated Mg2+. Ion-molecule reactions between Mg+(H2O)(16) and O-2 or CO2 are calculated to be highly exothermic. Initially, a solvent-separated ion pair is formed, with the hexa-coordinated Mg2+ ionic core being well separated from the O-2(center dot-) or CO2 center dot-. Rearrangements of the solvation structure are possible and produce a contact-ion pair in which one water molecule in the first solvation shell of Mg2+ is replaced by O-2(center dot-) or CO2 center dot-.