Infrared and DFT Investigations of the XC⋮ReX₃ and HC⋮ReX₃ Complexes:  Jahn−Teller Distortion and the Methylidyne C−X(H) Stretching Absorptions

The XC⋮ReX₃ complexes (X = F, Cl) are produced by CX₄ reaction with laser-ablated Re atoms, following oxidative C−X insertion and α-halogen migration in favor of the carbon−metal triple bond and are identified through the observation of characteristic absorptions in the argon matrix infrared spectra and comparison with vibrational frequencies calculated by density functional theory. The methylidyne C−F and C−Cl stretching absorptions are observed near 1584 and 1328 cm^-1, and the C−H stretching modes for HC⋮ReX₃ at 3104 and 3097 cm^-1, respectively, which are substantially higher than the precursor stretching modes and in agreement with the general trend that higher s-orbital character in carbon hybridization leads to a higher stretching frequency. The Jahn−Teller effect in the doublet-state XC⋮ReX₃ and HC⋮ReX₃ complexes gives rise to distorted structures with C_s symmetry and two equivalent longer Re−X bonds and one slightly shorter Re−X bond.