Tris{[tris(2-hydroxymethyl)methyl]ammonium} D-3-phosphoglycerate at 150 K and tris(cyclohexylammonium) D-3-phosphoglycerate ethanol solvate at 85 K

The structures of the D-3-phosphoglycerate trianion in the tris{[tris(2-hyd roxymethyl)methyl]ammonium} salt, 3C(4)H(12)NO(3)(+). C3H4O7P3-, (I) and in the tris(cyclohexylammonium) ethanol solvate, 3C(6)H(14)N(+). C3H4O7P3-.-C 2H5OH, (II), have been determined by X-ray analyses at 150 and 85 K, respec tively. A notable feature of (I) is the shortest P-O(ester) bond [1.607 (2) Angstrom] found so far for the completely ionized phosphate ester group. I n contrast, in (II), this bond length is 1.627(2) Angstrom, similar to that observed in doubly ionized phosphate ester groups. In (II), the carboxylat e group is twisted by -23.5 (4)degrees relative to the alpha-hydroxyl group , as indicated by the O1-C1-C2-O2 torsion angle, whereas in (I), the O2-C2- C1-O1 system is almost planar. Both crystal structures are stabilized by hy drogen bonds utilizing all N and O atoms.