Matrix infrared spectra and DFT calculations of the reactive MHx (x=1, 2, and 3), (H2)MH2, MH2+, and MH4- (M = Sc, Y, and La) species

Laser-ablated Sc, Y, and La react with molecular hydrogen to give MH, MH2+, MH2+, MH3, and MH4- (M = Sc, Y, and La) during condensation in excess argon for characterization by matrix infrared spectroscopy. Annealing forms the dihydrogen complex (H-2)MH2, which can be reduced to MH4- by electron capture. The (HD)MHD complex exchanges hydrogen positions on broadband photolysis to form primarily the (D-2)MH2 complex. Doping the samples with CCl4 to capture ablated electrons markedly increases the MH2+ infrared band intensities and decreases the MH4- absorptions. Further annealing produces higher (H-2)(2)MH2 complexes, which also exchange hydrogen positions. The reaction products are identified by deuterium and deuterium hydride isotopic substitution. DFT and MP2 theoretical calculations are employed to predict geometries and vibrational frequencies of these novel molecules, complexes, anions, and cations. Charged species from laser-ablation contribute more to the spectra of group 3 reaction products than for any other transition metal. Experiments, using solid neon and pure deuterium provide complementary spectra and favor the higher (H-2)(2)MH2 complexes.