Résumé : The Mössbauer spectra of a series of complexes R3SnX + aza-aromatic base have been recorded. It is found that the spectroscopic parameters (IS, QS, or their ratio p) bear no relation whatsoever to structural or electronic properties of the aromatic ligand bound to the tin atom. It is concluded that care should be exercised before drawing quantitative conclusions from Mössbauer data on such complexes. © 1967.