Comprehensive study of the structure of aluminum trihalides from electron diffraction and computation

The molecular geometries of the complete series of aluminum trihalides, AlX ₃ (X = F, Cl, Br, and I), are discussed based on new gas-phase electron diffraction (GED) experiments (AlCl ₃ and Al ₂Cl ₆) and on the reanalysis of our previous GED data (for the rest of the series) with an improved and analogous treatment of the temperature effect on the average bond lengths. This is the first time that all structure analyses are based on GED experiments of homogeneous vapors; either as pure monomers or dimers. The structures of other small oligomers as well as those of the crystals of aluminum trihalides are also discussed.