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

The cation complexes [ArB3O4]+, [ArB3O5]+, [ArB4O6]+ and [ArB5O7]+ 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 [ArB3O5]+, [ArB4O6]+ and [ArB5O7]+ cation complexes have planar structures each involving an aromatic boroxol ring and an argon-boron covalent bond. In contrast, the [ArB3O4]+ cation is characterized to be a weakly bound complex with a B3O4+ chain structure.