The syntheses of the linkage isomers trans-[Co (NH3)4 (NH2CH3)NO2]2+ and trans -[Co(NH3)4 (NH2CH3)ONO]2+ are reported. The methods of preparation of these complexes are based on the mechanism proposed earlier for the formation of the known parent pentaammines. The complexes are characterized by means of electronic, infrared and proton magnetic resonance spectroscopy. The trans configurations of the new complexes are established on the basis of their H-1 NMR spectra.