The dilithium silylamide [(Me2SiNtBuLi)2O]2shows in the temperature range between ambient temperature and 150 K three solid state phases with transition points at 253 K and 163 K which were characterised by means of X-ray diffraction and solid state NMR spectroscopy. In the high temperature phase the dimeric molecules of [(Me2SiNtBuLi)2O]2crystallize in the tetragonal space groupP42/nmc. It can be deducted from X-ray diffraction studies that, at room temperature, the four lithium atoms in [(Me2SiNtBuLi)2O]2are statistically distributed on two split positions at a distance of 0.89(1) Å. By cooling below 253 K the crystal transforms into an intermediate phase with space groupP42/n. The symmetry of the molecule is reduced from point symmetry (4) over bar 2m(D2d) to (4) over bar (S4). The split positions of the lithium atoms are found in different planes and their distance is slightly reduced from 0.89 Å to 0.81 Å. Solid state NMR spectroscopic measurements and powder diffraction analysis reveal the existence of a monoclinic low temperature phase below 163 K. From7Li MAS and13C CP/MAS NMR spectroscopic measurements follows furthermore that the disorder of the lithium atoms in the two higher temperature phases (above 163 K) is due to a local dynamic exchange of the four lithium atoms over eight possible positions in the molecule.7Li NMR measurements at variable MAS rates reveal a very small activation energy of 11 KJ/mol for the dynamic process with ex hange rates of the lithium atoms in the order of 5 to 15 K Hz. With respect to the lithium atoms in the order of 5 to 15 KHz. With respect to the lithium motions, the dynamics are intramolecular with an intermolecular coupling process due to van-der-Waals forces.