Abstract Ti(NMe 2) 4 is a monomeric species in the gas phase and in solution, and this remains true on crystallisation. The crystal structure is triclinic, with space group P 1 ¯ , and unit cell dimensions a = 8.277(6), b = 8.407(6), c = 11.167(7) Å, α = 105.36(4)°, β = 97.03(3)° and γ = 116.01(2)° at 105 K. Electron-diffraction measurements show that in the gas-phase Ti(NMe 2) 4 takes the form of a slightly flattened tetrahedron with overall S 4 symmetry. In the solid state the symmetry changes to C 1; the reduction of point-symmetry results from the twisting of one of the amino groups away from its gas-phase configuration. DFT calculations indicate that the energy of the C 1 structure lies only 0.2 kJ mol −1 above that of the S 4 conformer. The change in structure on crystallisation can be ascribed to the avoidance of prohibitively short intermolecular methyl–methyl interactions which would have been formed had the S 4 structure been retained.