Unsupported and supported Nd(C3H5)(3). dioxane and La(C3H5)(3).1.5 dioxane complexes were investigated by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), Raman spectroscopy and temperature-programmed reaction spectroscopy (TPRS). The obtained results allow conclusions concerning the structure and thermal stability of metal complexes, as well as their bonding properties. A structural model was developed for such allyl compounds based mainly on the vibrational spectroscopy data. This model was used to interpret the structural changes of these allyl-lanthanide complexes after being supported on methylaluminoxan (MAO)-modified silica (WITCO).