Synergism of primary and secondary interactions in a crystalline hydrogen peroxide complex with tin

Despite the significance of H₂O₂-metal adducts in catalysis, materials science and biotechnology, the nature of the interactions between H₂O₂ and metal cations remains elusive and debatable. This is primarily due to the extremely weak coordinating ability of H₂O₂, which poses challenges in characterizing and understanding the specific nature of these interactions. Herein, we present an approach to obtain H₂O₂–metal complexes that employs neat H₂O₂ as both solvent and ligand. SnCl₄ effectively binds H₂O₂, forming a SnCl₄(H₂O₂)₂ complex, as confirmed by ¹¹⁹Sn and ¹⁷O NMR spectroscopy. Crystalline adducts, SnCl₄(H₂O₂)₂·H₂O₂·18-crown-6 and 2[SnCl₄(H₂O₂)(H₂O)]·18-crown-6, are isolated and characterized by X-ray diffraction, providing the complete characterization of the hydrogen bonding of H₂O₂ ligands including geometric parameters and energy values. DFT analysis reveals the synergy between a coordinative bond of H₂O₂ with metal cation and its hydrogen bonding with a second coordination sphere. This synergism of primary and secondary interactions might be a key to understanding H₂O₂ reactivity in biological systems.