Matrix infrared spectra and density functional theory calculations of manganese and rhenium hydrides

Laser-ablated Mn and Re atoms react with H-2 upon co-condensation in excess argon and neon and in pure hydrogen to produce metal hydrides. The reaction products are identified through isotopic substitution (D-2, HD, and H-2 + D-2) and density functional theory calculations. The (7)Sigma(+) ground state diatomic MnH is observed at 1493.3 cm(-1) in solid neon, 1486.4 cm(-1) in hydrogen, and 1477.9 cm(-1) in argon. The ReH molecule gives a sharp band at 1985.0 cm(-1) in argon, which is suggested to be the (5)Sigma(+) ground state by DFT calculations. The MnH2 molecule provides nu(3) modes at 1600.8 cm(-1) in solid neon, 1598.0 cm(-1) in solid hydrogen, and 1592.3 cm(-1) in solid argon, and the analogous ReH2 molecule absorbs at 1646.4 cm(-1) in solid argon. In addition MnH2- is observed at 1465.6 cm(-1) in solid neon. The bonding properties of the first row transition metal dihydrides are compared, and reaction mechanisms of Mn and Re with H-2 are discussed. The novel ReH4 molecule absorbs at 2037.2 and 590.6 cm(-1). This work reports the first experimental evidence for neutral rhenium hydride molecules.