Synthesis and characterization of osmyl-amino acid complexes. Molecular structure of trans-dioxobis(glycinato)osmium(VI), OsO2(NH2CH2COO)2

Article abstract of DOI:10.1021/ic50221a019

The synthesis and characterization of stable and well-defined osmium(VI)-amino acid complexes is reported for the first time. The reaction of OsO₄ with glycine, DL-alanine, DL-valine, DL-leucine, DL-isoleucine, and DL-phenylalanine leads to the formation of dioxobis(amino acidato)osmium(VI) complexes, which are isolable intermediates in a complex reaction sequence. The structure of the glycinato compound has been determined by X-ray diffraction. Crystals of the complex belong to the monoclinic space group P2₁c with a = 5.041 (1) ?, b = 7.210 (2) ?, c = 10.885 (2) ?, β = 101.68 (1)°, V = 387.4 ?³, and Z = 2. Mo Ka radiation of λ = 0.710 73 ? was used and the structure solved by determining the position of the osmium atoms with use of the Patterson heavy-atom method and then locating other atoms in succeeding difference Fourier syntheses to R = 0.028 for 1441 reflections. The molecule is composed of two deprotonated NH₂CH₂COO^- ions chelated to a linear O-Os-O moiety through oxygen and nitrogen atoms. The Os-O distance of 1.731 (3) ? indicates the presence of an osmyl group. The two nitrogen atoms are trans to each other, and the molecule has a center of symmetry. Elemental analyses indicate that all six amino acids produce similar complexes. Infrared spectra of the complexes from 300 to 4000 cm^-1 exhibit features common to those reported for planar amino acidato complexes of other transition metals. Although ambiguity in assignments of some important vibrational modes cannot be resolved, the spectral data indicate that all six reported complexes have similar structures.