Infrared spectra and density functional theory calculations of group 4 transition metal sulfides

Laser-ablated titanium, zirconium, and hafnium atoms react with discharged sulfur vapor during co-condensation in excess argon. The primary reaction product MS2 molecules are identified for the first time, and evidence for metal monosulfides is also presented. The nu(1) and nu(3) modes for TiS2, ZrS2, and HfS2 absorb at 533.5 and 577.8 cm(-1), 502.9 and 504.6 cm(-1), and 492.2 and 483.2 cm(-1), respectively, in solid argon. On the basis of the isotopic frequencies for the nu(3) modes, the bond angles of TiS2, ZrS2, and HfS2 are determined as 113 +/- 4degrees, 107 +/- 4degrees, and 108 +/- 4degrees. DFT/B3LYP calculations predict (1)A(1) ground states and bond angles of 113.3degrees, 108.5degrees, and 109.5degrees, for the MS2 molecules, M = Ti, Zr, and Hf, respectively, and frequencies in excellent agreement with the observed values. The same calculation also predicts (3)Delta ground states for TiS and ZrS, the (1)Sigma(+) ground state for HfS, and frequencies in agreement with the observed values.