Matrix Infrared Spectra and Density Functional Theory Calculations of Manganese and Rhenium Hydrides

Abstract

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 Σ + 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 Σ + ground state by DFT calculations. The MnH 2 molecule provides ν 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 ReH 2 molecule absorbs at 1646.4 cm -1 in solid argon. In addition MnH 2is 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 ReH 4 molecule absorbs at 2037.2 and 590.6 cm -1 . This work reports the first experimental evidence for neutral rhenium hydride molecules.

Tetrahydrides of third-row transition elements: Spin-orbit coupling effects on the stability of rhenium tetrahydride

“…It was found that this is lower in energy than the dissociation limit, ReH 2 ͑ 6 ⌺ g + ͒ +H 2 ͑ 1 ⌺ g + ͒, by 8.8 kcal/mol after dynamic correlation effects are considered by using the MRMP2 method. This is consistent with previous results reported by Andrews et al 27 Since the spinmultiplicities of the lowest states are different, the dissociation reaction of ReH 4 cannot occur without electronic transition from the lowest quartet state to the lowest sextet state. This transition can easily occur because of the strong SOC effects among low-lying states in such heavy metal compounds.…”

“…This conclusion is consistent with the previous experimental suggestion reported by Wang and Andrews. 27…”

“…24 Although there are only small amount of rhenium compounds in nature, it has been reported that these compounds can be used as effective catalyzes for the activation of C-H bonds 28,29 as well as hydrogen strorages. 27 In the light of ReH 4 possibly possessing the Jahn-Teller distortion, along with large SOC, it would be interesting for us to explore further the potential energy surface of ReH 4 . This paper focuses on SOC effects on the stability of ReH 4 .…”

Effect of Mn and Fe on the Reactivity of Sulfated Zirconia toward H2 and n-Butane: A Diffuse Reflectance IR Spectroscopic Investigation

“…17,33 Molecular MnH or MnH 2 are also observed at lower wavenumbers (1493.3 cm -1 or 1600.8 cm -1 in solid neon). 38 Vibrations of Mn-H in complexes occur at higher frequencies, which range from 1782 cm -1 in HMn(CO) 5 to 1900 cm -1 in HMn(CO) 2 (π-Cp)SiPh 3 . 39,40 Thus, zirconium or manganese hydrides are unlikely to cause the vibrations.…”

An analysis of the rotational, fine and hyperfine effects in the (0,0) band of the A7Π–X7Σ+ transition of manganese monohydride, MnH

“…[1,2]. Recent studies include the identification of MnH via cavity ring-down spectroscopy in the laser vaporization of manganese in the presence of CH 4 [3], and the observation of vibrational transitions within the X 7 R + state of matrix isolated MnH [4]. Most recently Gordon et al [5] have recorded and analyzed the Fourier transform infrared emission spectra for the vibration-rotation bands from v = 1 fi 0 to v = 3 fi 2 bands of the X 7 R + state, where MnH was produced in a high-temperature discharge.…”