Two organotin(IV) complexes, [Sn(C 6 H 5 ) 3 HL 1 ] (1) and [Sn(C 2 H 5 ) 2 (1κO,2κO-H 3 L 2 )(1κO 2 -H 3 L 2 )(μ 3 -O)] 2 (2), were isolated upon interaction of Ph 3 SnCl and Et 2 SnO with 2-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)benzoic acid (H 2 L 1 ) and 2-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene) hydrazinyl)benzoic acid (H 4 L 2 ), respectively, in toluene solution. Complexes 1 and 2 were characterized by IR and NMR spectroscopies, elemental and single crystal X-ray diffraction analyses. While in 1 the (HL 1 ) – ligand binds the metal in a chelating bidentate mode, in 2 the (H 3 L 2 ) – anion acts not only as a chelating bidentate but also as a bridging bidentate donor. The in vitro antiproliferative activity against human colorectal carcinoma (HCT116) and human hepatocellular carcinoma (HEPG2) cells lines demonstrated that compound 1 possesses high in vitro antiproliferative activity with IC 50 values of 0.0284 ± 0.0001 μM and 0.287 ± 0.0001 μM for HCT116 and HEPG2 cells, respectively.