Spectroscopic study of cobalt(III) β-aminoethylate complexes

Aqueous solutions of fac- and mer-isomers of [CO(NH2C2H4O)(3)]. 3H(2)O were investigated by the C-13 NMR spectroscopy method. The spectrum of the fac-isomer exhibited only two signals with delta 47.08 (C-N) and 63.87 (C-o) ppm, which points to a high symmetry of the compound and to the presence of a complex in the solution (unlike the crystal) with one type of polyhedron (probably, of a trigonal-prismatic type). The spectrum of the mer-isomer solution is more complicated: the C-N and C-o signals are split into three components with delta 48.81,47.18, and 46.11 ppm and 64.70, 64.45, and 64.23 ppm, respectively. This fact confirms deterioration of the symmetry of the coordination polyhedron due to nonequivalence of beta -aminoethylate ions bound to the central atom. The successive protonation of the complexes does not affect either the symmetry of the coordination sphere of the fac-isomer or the asymmetry of the coordination sphere of the mer-isomer. The H-1, C-13, Co-59 NMR and IR spectroscopy data made it possible to suggest that both fac-[Co(NH2C2H4O)(3)] fragments in the binuclear fac-[H-3(Co(NH2C2H4O)(3))(2)](NO3)(3) complex are linked together by three symmetrical hydrogen bridges.