Ti(NMe2)(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 P1, and unit cell dimensions a = 8.277(6), b = 8.407(6), c = 11.167(7) angstrom, a = 105.36(4)degrees, beta = 97.03(3)degrees and gamma = 116.01(2)degrees at 105 K. Electron -diffraction measurements show that in the gas-phase Ti(NMe2)(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, 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. (c) 2005 Elsevier Ltd. All rights reserved.