Infrared spectra and density functional theory calculations of group 6 transition metal sulfides in solid argon

Laser-ablated chromium, molybdenum, and tungsten atoms react with discharged sulfur vapor during cocondensation in excess argon. On the basis of the metal isotopic splittings, S-34 isotopic substitution, and mixed S-32 + S-34 experiments, the primary reaction product MS2 molecules are identified. The S-M-S bond angles in the MS2 molecules are determined from isotopic frequencies as 115degrees +/- 4degrees, 114degrees +/- 3degrees, and 114degrees +/- 8degrees for M = Cr, Mo, and W, respectively. Other reaction products, including CrS, CrS3, and WS3, are also characterized. DFT calculations using both B3LYP and BPW91 functionals produce consistent results for the Mo and W compounds and are in excellent agreement with experimental frequencies. For chromium sulfides, the BPW91 functional calculations give satisfactory results.