Hydrazine N鈥揘 Bond Cleavage over Silica-Supported Tantalum-Hydrides

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• 作者：Hong-Peng Jia ; Eric Gour茅 ; Xavier Solans-Monfort ; Jessica Llop Castelbou ; Catherine Chow ; Mostafa Taoufik ; Odile Eisenstein ; Elsje Alessandra Quadrelli
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：December 21, 2015
• 年：2015
• 卷：54
• 期：24
• 页码：11648-11659
• 全文大小：671K
• ISSN：1520-510X

文摘

Hydrazine reacts with silica-supported tantalum-hydrides [(鈮iO)₂TaH_x] (x = 1, 3), 1, under mild conditions (100 掳C). The IR in situ monitoring of the reaction with N₂H₄ or ¹⁵N₂H₄, and the solid-state MAS NMR spectra of the fully ¹⁵N labeled compounds (CP ¹⁵N, ¹H鈥?sup>15N HETCOR, ¹H鈥?sup>1H double-quantum, and ¹H鈥?sup>1H triple-quantum spectra) were used to identify stable intermediates and products. DFT calculations were used for determining the reaction pathway and calculating the ¹⁵N and ¹H NMR chemical shifts. Combining the experimental and computational studies led to the following results. At room temperature, only hydrazine adducts, 1-N₂H₄, are formed. Upon heating at 100 掳C, the hydrazine adducts are converted to several species among which [(鈮iO)₂Ta(鈺怤H)(NH₂)], 2, [(鈮iO)₂TaH(NH₂)₂], 3, and [(鈮iO)₂TaH₂(NH鈥擭H₂)], 4, were identified. The final product 2 is also formed in the reaction of N₂ with the same silica-supported tantalum-hydride complexes, and the species identified as 3 and 4 had been previously suggested by DFT studies as intermediates on the reaction pathway for N鈥揘 cleavage in N₂. The present computational studies (cluster models with M06 functional complemented by selected calculations with periodic calculations) show that 2 is formed via 3 and 4, with either N₂ or N₂H₄. This strengthens the previous proposal of the existence of 3 and 4 as intermediates in the reaction of N₂ with the tantalum-hydrides. However, the reaction of N₂ does not imply the formation of N₂H₄ or its hydrazido monoanionic or dianionic ligand as an intermediate. For this reason, this study informs both on the similarities and differences of the reaction pathways involving N₂ and N₂H₄ with tantalum-hydrides.