Mechanistic Insights into a Gas–Solid Reaction in Molecular Crystals: The Role of Hydrogen Bonding

Hydrogen bonding leads the way: Reaction of nonporous crystalline coordination compound 1 with HCl gas results in conversion into the crystalline salt 2 (see picture) following chemisorption and insertion of HCl into CuN bonds. Powder diffraction studies show that [CuBr2Cl2]2− ions formed in 2 are reoriented to maximize the strength of hydrogen bonds and halogen bonds by preferentially involving Cl rather than Br ligands as acceptor sites.