N,N'-Bis[tris-(hy-droxy-meth-yl)meth-yl]propane-1,3-di-amine (bis-tris propane).

The title compound, C11H26N2O6, used for the preparation of buffer solutions and high-nuclearity coordination complexes, crystallizes with a half mol-ecule in the asymmetric unit. The full mol-ecule is completed through mirror symmetry m in the space group Pnma. The mol-ecular shape is bent and, as a consequence, some H atoms are disordered to avoid too short H⋯H intra-molecular contacts. Mol-ecules in the crystal are linked via O-H⋯N and N-H⋯O hydrogen bonds, forming chains along [100], which are further packed through other O-H⋯O hydrogen bonds between hy-droxy groups. The here-reported structure probably represents the less-stable form in a set of polymorphs.