Abstract A number of tin (IV) complexes, Sn (LL) 2 X 2, have been prepared in which LL is a 4-pyronate or 4-pyridinonate ligand and X is chloride or alkoxide. UV-vis, IR and NMR (1 H, 13 C, 119 Sn) spectra are reported for these complexes. Reactivities have been established through kinetic studies of nucleophilic substitution in acetonitrile solution. Ligand effects on spectra and reactivity are discussed and compared with those for similar metal (IV) ...