T-Shaped Stannyliumylidene Ion: Synthesis, Reactivity, and Redox Catalysis.

We report the synthesis and characterization of a T-shaped, 8-electron stannyliumylidene ion bearing a rigid acridane-based pincer ligand. This cationic Sn(II) complex exhibits pronounced ambiphilic reactivity, participating in electrophilic, nucleophilic, and σ-bond activation reactions. All derived compounds were characterized by nuclear magnetic resonance spectroscopy, single crystal x-ray diffraction analysis, and high-resolution mass spectrometry. Density functional theory calculations reveal the coexistence of a lone pair of electrons and a vacant 5p-orbital at the tin center, which rationalizes the experimentally observed dual reactivity. Remarkably, the transition metal-like electronic structure enables this organotin(II) species to act as an efficient catalyst for transfer hydrogenation of azoarenes and imines using NH3BH3 as hydrogen source. Combined experimental and computational mechanistic studies reveal a distinct catalytic platform based on Sn(II)/Sn(IV) redox cycle at a single tin(II) center. This work demonstrates the first Sn(II)/Sn(IV) catalyzed reduction of unsaturated bonds, offering a paradigm for mimicking transition metal reactivity through rationally designed main group systems in mediating diverse chemical transformations.