Novel triorganotin(IV) derivatives of β-diketonate Q ligands (HQ in general, in detail HQfur=1-phenyl-3-methyl-4-(2-furancarbonyl)-pyrazol-5-one, HQthi=1-phenyl-3-methyl-4-(2-thienylcarbonyl)-pyrazol-5-one) of general formula (Q)SnR3·xH2O (R=Ph, x=0; R=Bun or Me, x=1) have been synthesized and spectroscopically and thermally characterized. Triphenyltin(IV) complexes have been isolated as anhydrous compounds while trialkyltin(IV) are always monohydrated. The structures of (Qfur)SnPh3 and (Qthi)SnMe3(OH2) are recorded. The tin atoms are five-coordinate in both. In the first, the pyrazolonate ligand behaves as an O,O′-bidentate; there are two similar but independent molecules in the structure. In the quasi-trigonal-bipyramidal environments, Sn–O(acyl) are 2.478(3), 2.364(3), Sn–O(pyrazolonate) 2.050(2), 2.079(2), Sn–C 2.123(4)–2.162(3)Å with the longer O(acyl) and a phenyl group quasi-trans (O–Sn–C 162.5(1), 160.8(1)°). In (Qthi)SnMe3(OH2), the three methyl groups are equatorial (Sn–C 2.1259(9)–2.1380(8)Å); Sn–O(Qthi,OH2) are 2.2143(5), 2.3350(6)Å, O–Sn–O 175.36(2)°. Trimethyltin(IV) derivatives decompose on heating with release of H2O and SnMe4 and formation of (Q)2SnMe2. Decomposition occurs also within two days after dissolution of (Q)SnMe3(OH2) in chloroform.