PubMed · 4079761
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F R Salemme. 1985. Protein crystallization by free interface diffusion.. https://doi.org/10.1016/0076-6879(85)14013-9
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In crystals of O-phospho-DL-threonine and O-phospho-L-threonine, the molecules are zwitterions HO3-POCH-(CH3)CH(NH3+)CO2H linked by three-dimensional networks of strong P-O-H...O = P, C-O-H...O = P, N-H...O = P and N-H...O = C hydrogen bonds with (O...O) = 2.55 (3) A and (N...O) = 2.84 (4) A. Both the molecular conformations and the nearest-neighbor hydrogen-bonded surroundings are very similar in the racemic and enantiomeric crystals of the threonine compounds, but earlier studies of crystals of the analogous serine compounds have shown that the serine zwitterions HO3-POCH2CH(NH3+)CO2H have different conformations about the C beta-O gamma-P phosphate ester bonds and different hydrogen-bonded surroundings.
The title crystal, C12H11N3O4, contains three essentially identical molecules in the asymmetric unit. The triazole rings in the three independent molecules are planar within 0.014 A. The N atom containing the phenyl substituent is trigonal, the sum of the three bond angles being 359.5 degrees. The other two N atoms are slightly pyramidal, the sum of the three bond angles being 346 degrees. The two acetyl groups are twisted out of the plane of the triazole ring by an average of 33 degrees and are trans to each other.
Selective crystallization of a solution of lithium isodicyclopentadienide, (isodiCp)Li, in dry thf or diethyl ether under argon has produced two lithium complexes: (isodiCp)Li(TMEDA), [Li(C10H11)(C6H16N2)], (4), and [Li(12-crown-4)2]+. [Li(isodiCp)2]-, [Li(C8H16O4)2]-[Li(C10H11)2], (5). In (4) the Li+ ion is coordinated to the two N atoms of the disordered TMEDA and is eta 5-coordinated to the Cp ring of the isodiCp ligand. The Li-(Cp ring centroid) distance is 1.906 (7) A. In (5) there are two independent half-molecules of the anion and one molecule of the cation in the asymmetric unit. In each anion, the Li+ ion occupies a crystallographic inversion center and is eta 5-coordinated to the two Cp rings of two isodiCp ligands. The Cp rings are in a staggered arrangement, as required by the inversion center. The Li-(Cp ring centroid) distances for the two anions are 1.987 (3) and 2.008 (3) A. In the cation of (5), the Li+ ion is coordinated to two 12-crown-4 ligands, one of which is disordered. Both (4) and (5) exhibit exo coordination of the Li+ ion to the isodiCp ligand, with a resultant slight endo bending of this ligand.