Résumé : The synthesis and spectroscopic characterization of diorganotin(IV) bis(difluorobenzoates) [F2C6H3COO]2SnR2 [type a] and bis[diorgano(difluorobenzoato)tin(IV)] oxides {[(F2C6H3COO)R2Sn]2O}2 [type b] are described. An X-ray structure study has revealed compound 3b, {[(2,6-F2C6H3COO)(n-C4H9)2Sn]2O}2, to be dimeric and built around a planar Sn2O2 ring. The crystals are triclinic P1 with the cell dimensions a = 11.935(13), b = 12.3675(14), c = 12.974 Å, α = 92.89(8), β = 84.32(7), γ = 67.49(9)°; Z = 1, with the dimer being centro-symmetric. Selected compounds have been tested in vitro against two human tumour cell lines, MCF-7 (a mammary tumour) and WiDr (a colon carcinoma), and exhibit promising cytotoxicities. © 1993.