A crystalline stannyne

The synthesis of heteronuclear alkyne analogues incorporating heavier group 14 elements (R¹–C≡E–R², E = Si, Ge, Sn, Pb) has posed a long-standing challenge. Neutral silynes (R¹–C≡Si(L)–R²) and germynes (R¹–C≡Ge(L)–R²) stabilized by a Lewis base have achieved sufficient stability for structural characterization at low temperatures. Here we show the isolation of a base-free stannyne (R¹–C≡Sn–R²) at room temperature, achieved through the strategic use of a bulky cyclic phosphino ligand in combination with a bulky terphenyl substituent. Despite an allenic structure with strong delocalization of π-electrons, this compound exhibits adjacent ambiphilic carbon and tin centres, forming a carbon–tin multiple bond with ionic character. The stannyne demonstrates reactivity similar to carbenes or stannylenes, reacting with 1-adamantyl isocyanide and 2,3-dimethyl-1,3-butadiene. Additionally, its carbon–tin bond can be saturated by Et₃N·HCl or cleaved by isopropyl isocyanate.