Abstract
The anhydrous di-iodyl carbonate (IO(2))(2)[CO(3)] has been synthesized in a laser-heated diamond anvil cell at 30(2) GPa and 1600(200) K by a reaction of I(2)O(5) with CO(2). Its monoclinic crystal structure (C2/c with Z = 4) was determined from synchrotron single crystal X-ray diffraction data. The experimental structural model was confirmed by density functional theory based calculations in combination with experimental Raman spectroscopy. (IO(2))(2)[CO(3)]-C2/c belongs to the family of sp(2)-carbonates, and its crystal structure is characterized by the presence of nearly trigonal-planar [CO(3)](2-) groups. In contrast to other iodide-containing carbonates, in this structure the iodine atoms are present as small and highly oxidized I(5+)-cations and not as large I(-)-anions. The I(5+)-cations are coordinated by seven oxygen atoms. The successful synthesis of (IO(2))(2)[CO(3)]-C2/c represents a significant enlargement of the crystal chemistry of carbonates, as this chemically simple carbonate demonstrates that anhydrous carbonates with highly charged cations can be formed and that sp(2)-carbonates hosting a positively charged halogen atom as the only cation can be synthesized.