Complexes of divalent tin 7–12 with diethylenetriamines 1–3 and related ligands 4–6 were prepared from Lappert's stannylene, Sn[N(SiMe3)2]2, and the corresponding ligands. Reactivity of the stannylenes in insertion, oxidation and [1+4] cycloaddition reactions were studied. Composition and structures of the products were confirmed by elemental analyses and multinuclear (1H, 13C, 19F, and 119Sn) NMR spectroscopy. Crystal structures of the diethylenetriamines 1, 2, stannylenes 7, 8 and the product of the reaction of stannylene 8 with an azide, which contains an eight‐membered (SnNPO)2 ring, were determined by X‐ray diffraction study.