Résumé : The synthesis and characterization of (4,7-dioxaoctyl)triphenyltin (1), (4,7,10-trioxaundecyl)triphenyltin (2), (4,7,10,13-tetraoxatetradecyl)triphenyltin (3), and (4,7-dioxaoctyl)phenyldichlorostannane (4) are reported. Investigatons using 1H-, 13C-, and 119Sn-NMR, gradient assisted 2D 1H-13C HMBC and HMQC NMR, 1D 1H-119Sn HMQC NMR demonstrate that 1-3 are essentially tetracoordinated. By contrast, the structure of compound 4, determined by X-ray diffraction methods, reveals a hexacoordinated, distorted octahedral geometry, in which the 4,7-dioxaoctyl ligand is tridentate, with a facial arrangement of the C, O, O atoms with respect to tin. NMR investigations reveal that this structure exists in solution, but is labilized by a double ring opening-closing mechanism.