Matrix Isolation Infrared Spectroscopic And Theoretical Studies On The Reactions Of Transitional Metal Mono- And Dioxides With Monochloromethane

The reactions of transitional metal monoxides (ScO, YO, NbO, TaO, TiO, and ZrO) and dioxides (NbO₂, TaO₂, TiO₂ and ZrO₂ ) with monochloromethane have been investigated by matrix isolation infrared spectroscopic and quantum chemical calculations. The metal monoxide and dioxide molecules were prepared by laser-evaporation of higher metal oxide targets. The reaction intermediates and products are identified by isotopic substitution and density functional theoretical calculations. The reaction mechanism and periodic trends are discussed.In the excess argon matrice, the initial step of the MO + CH₃Cl is formation of MO(CH₃Cl) complex. For the complex, one hydrogen or chlorine atom of CH₃Cl transferred to form isomer upon different strong light irradiation. In the ScO and YO experiments, the MO(CH₃Cl) complex required higher activation energy in isomerization, and so upon full UV light irradiation it isomized to two kinds of isomer CH₂ClMOH, CH₃OMCl. In the niobium and tantalum experiments, the activation energies of isomerization are much lower. Upon the visible light irradiation, the hydrogen atom of the MO(CH₃Cl) complex converted to the M atom of MO to form CH₂ClM(O)H molecule. In the Ti and Zr experiments, the chlorine atom of the complex transferred. Upon UV-visible light irradiation (250 <λ< 500 nm), TiO(CH₃Cl) isomerized to the CH₃Ti(O)Cl molecule. The CH₃Zr(O)Cl molecule was observed on deposition and increased dramatically on annealing, which indicated that the formation of the CH₃Zr(O)Cl molecule reqiured much lower activation energy.The reactions of metal monoxides with monochloromethane are summarized in Scheme1: The reactions of the metal dioxide molecules (MO₂, M=Nb, Ta, Ti and Zr) with monochloromethane also produced the MO₂(CH₃Cl) complexes, whose binding energies are much larger than those of the corresponding MO(CH₃Cl) complexes. The MO₂(CH₃Cl) complexes rearranged to the CH₂ClM(O)OH(M=Nb and Ta) isomer upon UV light irradiation in the niobium and tantalum experiments, and on the same irradiation condition they rearranged to the CH₃OM(O)Cl (M=Ti and Zr) isomer in the titanium and zirconic experiments.The reactions of metal dioxides with monochloromethane are summarized in Scheme2:...