The reactivity of ClMn(H2O)+ towards small organic compounds (L) was examined in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. The organic compounds studied are aliphatic and aromatic alcohols, aliphatic amines, ketones, an epoxide, an ether, a thiol and a phosphine. All the reactions lead to the formation of the ClMn(H2O)(L)+ complex, which dissociates by loss of the H2O molecule. In general, the reactions were found to occur with high efficiencies (>85%), indicating them to be exothermic. Electron transfer was also observed between ClMn(H2O)+ and compounds with low ionization energies (IE), to form the molecular ion (L+•) of the analyte. Based on these observations, the IE of ClMn(H2O)+ is approximated to be 8.1 ± 0.1 eV. Thus, the utility of ClMn(H2O)+ as a chemical ionization reagent in mass spectrometry is expected to be limited to organic compounds with IEs greater than 8 eV. Copyright © 2012 John Wiley & Sons, Ltd.