Complexes formed between the compounds PrnSnCl3, Prn2SnCl2, and PhnSnCl4–n(n= 1–3) and the Lewis bases piperidine, morpholine, β-picoline, γ-picoline, and isoquinoline have been studied by means of the Mössbauer effect. In several cases the signs of the quadrupole coupling constants, e2qQ, were determined. On this basis the complexes of Ph3SnCl have been assigned a trigonal bipyramidal structure with C–Sn–C bond angles of ca. 120°. The adducts of Ph2SnCl2 and Prn2SnCl2 with morpholine have a cis-arrangement of the organo-groups, whilst the other complexes have a trans-configuration. The nature of the bonding in these compounds and its influence on the Mössbauer parameters are also discussed.