Methane activation by laser-ablated V, Nb, and Ta atoms: Formation of CH3-MH, CH2=MH2, CHMH3-, and (CH3)2MH2 |
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Authors: | Cho Han-Gook Andrews Lester |
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Affiliation: | Department of Chemistry, University of Incheon, 177 Dohwa-dong, Nam-ku, Incheon 402-749, South Korea. |
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Abstract: | Methane activation by group 5 transition-metal atoms in excess argon and the matrix infrared spectra of reaction products have been investigated. Vanadium forms only the monohydrido methyl complex (CH3-VH) in reaction with CH4 and upon irradiation. On the other hand, the heavier metals form methyl hydride and methylidene dihydride complexes (CH3-MH and CH2=MH2) along with the methylidyne trihydride anion complexes (CHMH3-). The neutral products, particularly the methylidene complex, increase markedly on irradiation whereas the anionic product depletes upon UV irradiation or addition of a trace of CCl4 or CBr4 to trap electrons. Other absorptions that emerge on irradiation and annealing increase markedly at higher precursor concentration and are attributed to a higher-order product ((CH3)2MH2)). Spectroscopic evidence suggests that the agostic Nb and Ta methylidene dihydride complexes have two identical metal-hydrogen bonds. |
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