Structural Characterization of Bis[N-(o-Hydroxybenzyl-(S)-Leucinato)]cobaltate(III) Anion. Tyrosine-Like Model Complex with Structurally Inequivalent Chelate Rings

Abstract

[Co(NH3)4(H2O)2]OH . [Co(ohb-(S)-Leu)2] . 2 H2O (ohb, o-hydroxybenzyl) was characterized by single-crystal X-ray diffraction which shows that both ligands in the [Co(ohb-(S)-Leu)2]- anion assume facial coordination mode with all donor atoms trans to each other, proposed on the basis of UV-VIS and 13C NMR spectroscopy, with R,S configuration of secondary N atoms. Compound crystallizes in the tetragonal space group I41 with unit cell dimensions a = 22.173(7), c = 13.270(2) Å, V = 6 524 Å3, Z = 4. Structural data show that both ligands are not equivalent. Bond angles and bond lengths depend on whether secondary N atoms adopt R or S configuration. The average bond lengths are shorter when the ohb-(S)-Leu ligand coordinates with (N)R configuration.