Tetrahydrometalate Species VH2(H2), NbH4, and TaH4: Matrix Infrared Spectra and Quantum Chemical Calculations

Laser ablated V, Nb, and Ta atoms react with molecular hydrogen in excess neon at 4 K to give vanadium, niobium, and tantalum dihydrides that further react with H-2 to form VH2(H-2), NbH4, and TaH4. The reaction products are identified by deuterium and deuterium hydride isotopic substitution. DFT and CCSD theoretical calculations are used to predict energies, geometries, and vibrational frequencies for these novel metal hydrides complex and molecules. The vanadium dihydride hydrogen complex, VH2(H-2), is identified, while the niobium and tantalum tetrahydrides, NbH4 and TaH4, with D-2d symmetry structures are confirmed. Reactions of group 5 metal atoms with H-2 condensing in solid hydrogen gave VH2(H-2) and the higher tetrahydride hydrogen complexes NbH4(H-2)(4) and TaH4(H-2)(4).