Preparation and characterization of chemically bonded argon-boroxol ring cation complexes.

The cation complexes [ArB(3)O(4)](+), [ArB(3)O(5)](+), [ArB(4)O(6)](+) and [ArB(5)O(7)](+) were prepared via a laser vaporization supersonic ion source in the gas phase. Their vibrational spectra were measured via mass-selected infrared photodissociation spectroscopy. Spectroscopy combined with quantum chemical calculations revealed that the [ArB(3)O(5)](+), [ArB(4)O(6)](+) and [ArB(5)O(7)](+) cation complexes have planar structures each involving an aromatic boroxol ring and an argon-boron covalent bond. In contrast, the [ArB(3)O(4)](+) cation is characterized to be a weakly bound complex with a B(3)O(4)(+) chain structure.