The gas phase ion chem. of Cr(CO)6 and Mo(CO)6 with NH3 was studied by high pressure chem. ionization and Fourier transform ion cyclotron resonance mass spectrometry. Reactions in which CO is displaced by NH3 give M(CO)x(NH3)y+ from M(CO)n+ (n = 2-5, M = Cr, Mo) and NH3 mols., through complex pathways identified by double resonance expts. The highest mass ion is M(CO)6+, which is inert to NH3 and its neutral precursor M(CO)6. The formation of NH3-substituted ions involves multiple losses of CO and abundance of Mo(CO)x(NH3)y+ is higher than that of the corresponding Cr(CO)x(NH3)y+ species. Results obtained by these 2 methods are correlated and discussed
