Cyclic Trinuclear Diorganotin(IV) Complexes – The First Tin Compounds Bearing Oximehydroxamate Ligands: Synthesis, Structural Characterization and High In Vitro Cytotoxicity

Abstract The reactions between equimolar amounts of R2SnO (R = Me 1, nBu 2) and N,2‐dihydroxy‐5‐[N‐hydroxyethanimidoyl]benzamide (H2L) under solvent reflux conditions (in toluene for 1 and methanol for 2) for ca. 4 h led to the formation of the trinuclear tin complexes [R2Sn(L)]3 (R = Me 3, nBu 4) isolated as colourless crystalline solids in ca. 85 % yield, which were characterized by IR, 1H, 13C and 119Sn NMR spectroscopy, elemental analysis and (for 4) by X‐ray diffraction. The trinuclear Sn core is stabilized by multiple intramolecular hydrogen bonding interactions involving the hydroxamate ligands, whereas the uncoordinated oxime functions interact through intermolecular H‐bonds leading to cyclic hexameric assemblies. These complexes are stable in air, soluble in common solvents and moderately in water and represent the first examples of tin species containing ligatedoximehydroxamic acids. Complex 4 exhibits high in vitrotumour‐inhibiting activity against the following human cell lines: promyelocyticfina leukemia (HL‐60), hepatocellular carcinoma (Bel‐7402), gastric carcinoma (BGC‐823) andnasopharyngeal carcinoma (KB). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)