Isomerism of the Metal Complexes Containing Multidentate Ligands. X. [CoN6]3+-Type Complexes Containing H2N(CH2CH2NH)nH (n=0–4)

The preparation, separation, and characterization of isomeric complexes of type [CoN6]3+, containing one, two, or three molecules of NH3, en, dien, trien, and tetren (n=0, 1, 2, 3, and 4, respectively for H2N(CH2CH2NH)nH) are reported. All the possible five stereoisomers for [Co(NH3)(en)(dien)]3+ and six stereoisomers for [Co(en)(trien)]3+ have been successfully isolated, but only three of four possible geometrical isomers could be obtained for [Co(NH3)(tetren)]3+. These were characterized by electronic, circular dichroism (CD), and 13C{1H} NMR spectroscopy. Conformational analyses were, also, carried out and the stability, or formation of each isomer at the equilibrium state, is discussed from the calculated strain-energy data and experimental formation ratios.