Infrared Spectra of CH₃−CrH, CH₃−WH, CH₂WH₂, and CH⋮WH₃Formed by Activation of CH₄with Cr and W Atoms

Abstract

Laser-ablated W atoms react with CH4 in excess argon to form the CH3-WH, CH2=WH2, and CH[triple bond]WH3 molecules with increasing yield in this order of product stability. These molecules are identified from matrix infrared spectra by isotopic substitution. Tungsten methylidene and methylidyne hydride molecules are reversibly interconverted by alpha-H transfers upon visible and ultraviolet irradiations. Matrix infrared spectra and DFT/B3LYP calculations show that CH[triple bond]WH3 is a stable molecule with C3v symmetry, but other levels of theory were required to describe agostic distortion for CH2=WH2. Analogous reactions with Cr gave only CH3-CrH, which is calculated to be by far the most stable product.

Observation and Characterization of CH3CH2–MH, (CH2)2–MH2, and CH3–C≡MH3 Prepared in Reactions of Ethane with Laser-Ablated Group 6 Metal Atoms

“…The observed photoreversible variations in the intensities of the product absorptions suggest that the product responsible for the i absorptions converts to those responsible for the m and y absorptions on visible irradiation and vice versa in UV irradiation. Similar photoreversibility was observed previously in the matrix reaction of Mo with CH 4 ; CH 3 –MoH converted to CH 2 MoH 2 and HCMoH 3 on visible irradiation via H-migration from C to Mo, and vice versa on UV irradiation via H-migration from Mo to C …”

“…Spectral assignments have been carried out on the basis of spectral variation by deuteration, correlation with the computed values, and previous studies on reactions of metal atoms with methane and methyl halides. − The observed i absorption at 1688.6 cm –1 is assigned to the Mo–H stretching mode of the insertion complex (CH 3 CH 2 –MoH) with its D counterparts at 1211.6 cm –1 (Table and S1). The H/D ratio 1.394 is appropriate for the vibrational mode.…”

“…Th and U produce similar products, whereas Re and Os generate only ethylidynes (CH 3 CMH 3 ), and Pt only the insertion complex . Reactions of Mo and W with methane produced the CH 3 –MH, CH 2 MH 2 , and HCMH 3 molecules, but Cr gave only the first insertion complex . The group 6 metal and methane reaction products provide a starting point for the new molecules to expect with ethane.…”

Reactions of Uranium Atoms with Ammonia: Infrared Spectra and Quasi‐Relativistic Calculations of the U:NH3, H2NUH, and HNUH2 Complexes

“…Do the bond dissociation energies in Table 4 imply that the NTh and NU bonds are anomalously strong? The analysis is complicated by the agostic interactions that are present in some of the compounds, the influence of which will contaminate the bond dissociation energies evaluated here (note that agostic interactions have little effect on CM distances41). The NHf and NW bonds are stronger than their CHf and CW counterparts by 151 or 148 kJ mol −1 , respectively.…”

Formation of unprecedented actinidecarbon triple bonds in uranium methylidyne molecules

“…These studies were extended to the accessible actinide metal atoms Th and U for the preparation of the first actinide methylidene species HXAnϭCH 2 (X ϭ H, F, Cl, Br) (38)(39)(40)(41). Although Mo and W reactions also formed the analogous H 2 XM'CH methylidynes (42)(43)(44)(45)(46), the H 2 XU'CH counterparts were energetically too high to be produced in these experiments (40). However, very recent investigations with the heavy metals Zr, Hf, and Re in trihalomethane reactions have demonstrated that the highly exothermic driving force for halogen transfer from carbon to heavy metal fosters the formation of the low-energy, very stable trihalo metal carbynes (47,48).…”