An aromatic noble-gas hydride: C(6)H(5)CCXeH

We report on the aromatic noble-gas hydride, C(6)H(5)CCXeH, identified in a xenon matrix using infrared spectroscopy and extensive quantum chemical calculations. This molecule is prepared by 250-nm photolysis of phenylacetylene (C(6)H(5)CCH) isolated in a xenon matrix and subsequent thermal mobilization of hydrogen atoms at about 40 K. The characteristic H–Xe stretching mode of C(6)H(5)CCXeH is observed at about 1500 cm(−1), and a number of other fundamentals also appear in the experimental spectra. The assignment is supported by deuteration experiments providing predictable shifts of the vibrational frequencies. The experimental and calculated spectra are in a good agreement. C(6)H(5)CCXeH is computationally lower in energy than the C(6)H(5)CC + Xe + H fragments by about 0.60 eV at the M06-2X/aug-cc-pVTZ-PP level of theory, which allows its formation at low temperatures. C(6)H(5)CCXeH is the first aromatic noble-gas hydride and the first halogen-free aromatic noble-gas compound.