Diorganotin(IV) derivatives of arylhydroxamic acids: synthesis, properties and antitumor activity

Series of diorganotin(IV) complexes of 4-X-benzohydroxamic acid X = NH₂ (HL₁), NO₂ (HL₂) or F (HL₃)] formulated as R₂SnL₂] and R₂Sn(L)]₂O (R = Me, Et, nBu or Ph) have been prepared and characterized by FT-IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopies, elemental analyses, FAB⁺-MS and melting point determination. They are stable in air, soluble in alcohols and in hydroalcoholic solution and, in some cases, in water. Their in vitro antitumor activity against a series of human tumor cell lines was tested and, in a few of them, is identical to, or even higher than, that of cisplatin. For the mononuclear dialkyltin compounds, the activity generally increases with the length of the carbon chain of the alkyl ligand, being higher for the complexes with benzohydroxamato ligands bearing an electron-acceptor substituent (X = NO₂ or F). No structure-activity relationship based on the Hammett’s σ_p constant, or related ones, has been recognized.