1,2,4,5‐Tetrazine‐Boron Halide Adduct Formation Unraveled in Solution and Solid State

1,2,4,5‐Tetrazines are electron‐deficient heterocycles with four nitrogen atom‐localized lone pairs potentially acting as Lewis bases. While it has been shown that tetrazines, as electronically amphiphilic ligands, undergo anion–π, π–π, and transition metal‐based adduct formation reactions, adducts of tetrazines with main group metal Lewis acids have not yet been structurally characterized. We report spectroscopic and single crystal X‐ray diffraction (SC‐XRD) analyses of tetrazine‐boron halide adducts in solution and in the solid state, respectively. With the aid of (diffusion‐ordered) nuclear magnetic resonance (DOSY‐)NMR spectroscopy dynamic equilibria between tetrazine‐boron halide adducts have been proven, while solid state structures show localized 1:1 tetrazine‐boron halide adducts.