Synthesis, structures, and crystalline packing features of [Co(tren)(aminoacidato-N,O)]X-2 center dot nH(2)O (X = ClO4-, I-)

The crystal structures of several novel compounds, trans(AT,t-N) isomers of [Co(tren) (DL-phenylalaninato)](ClO4)(2) (1), [Co-(tren) (L-phenylalaninat o)]I-2 . H2O (2), [Co(tren)(L-prolinato)]- H2O (3), [Co(tren)(L-tryptophana to)](ClO4)(2).(1)/2H2O (4), [Co(tren) (L-valinato)]I-2.(1)/2H2O (5), [Co(tr en)(L-isoleucinato)]I-2 (6), and [Co(tren) (L-leucinato)]I-2 (7), have been determined. Their packing arrangements indicate that the complex cations i n all of the compounds form helical strings running along their crystallogr aphic axes, for both chiral and racemic amino acidato species. Intermolecul ar double and single hydrogen bonds are formed by the carbonyl oxygens and amino hydrogens of the tren ligand or of the amino acidato moiety, either d irectly or by the assistance of water molecules of hydration. In this fashi on, [Co(tren)(amino acidato-N,O)](2+) is strung together into helical array s. In the racemic compounds, the complex cations of different strings have opposite chirality. Phenylalanine is racemized during the coordination proc ess, under mild pH (7.5-8.0) and temperature (60 degrees C). This is quite unusual. Finally, 1D and 2D (COSY) H-1 NMR spectra were recorded, in which compound 4 shows interesting cross-peak correlations between the phenyl pro tons and amino protons.