A series of nine novel diorganotin(IV) complexes of O,N,O' chelating ligands were synthesized viz., [n-Bu2Sn(L2)]2·0.25 (C6H14) (1), [Me2Sn(L1)]2·(C7H8) (2), [n-Bu2Sn(L1)]2·(C7H8) (3), [Me2Sn(L3)]2·(C7H8) (4), 2 [n-Bu2Sn(L3)]2·4 (n-Bu2Sn(L3)) (5), [Ph2Sn(L3)] (6), [Ph2Sn(L1)] (7), [Ph2Sn(L4)] (8) and [Ph2Sn(L2)] (9) and structurally characterized. The ligand scaffolds differ with respect to the chemical link between the coordinating N and O atoms, which is either an alkyl or an aryl moiety. Diffraction results indicate that the smallest methyl groups favor dimerization via Sn–O–Sn bridging and six-coordination at the cation. Among these dinuclear derivatives, more asymmetric oxygen bridges and longer Sn⋯Sn separations are found for the less nucleophilic phenolate O. In contrast, the bulky phenyl substituents prevent aggregation for both classes of ligands and always lead to five-coordinated mononuclear species. The n-Bu groups are sterically more demanding than Me but flexible, resulting in an intermediate behavior. When the O,N,O' ligand with phenolate O coordinates a Sn(n-Bu)2 fragment, a borderline situation occurs and both mono- and dinuclear complexes coexist in the same crystalline solid. The overall structural variety is reflected in a range of different Addison-τ5 [Addison et al., J. Chem. Soc., Dalton Trans.1984, 1349-1356] descriptors for five-fold coordination. For better comparability we introduce a slightly modified geometry index τ'5, in which the basal angle α is subtended by the organic substituents, regardless of its absolute value. τ'5 represents a sensitive indicator for the coordination geometry about SnIV. Tin NMR results revealed that all compounds exist as mononuclear pentacoordinated species in solution.