Ammonia Borane Dehydrogenation Promoted by a Pincer-Square-Planar Rhodium(I) Monohydride: A Stepwise Hydrogen Transfer from the Substrate to the Catalyst

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• 作者：Miguel A. Esteruelas ; Pau Nolis ; Montserrat Oliván ; Enrique Oñate ; Adelina Vallribera ; Andrea Vélez
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：July 18, 2016
• 年：2016
• 卷：55
• 期：14
• 页码：7176-7181
• 全文大小：422K
• 年卷期：0
• ISSN：1520-510X

文摘

The pincer d⁸-monohydride complex RhH{xant(PⁱPr₂)₂} (xant(PⁱPr₂)₂ = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) promotes the release of 1 equiv of hydrogen from H₃BNH₃ and H₃BNHMe₂ with TOF_50% values of 3150 and 1725 h^–1, to afford [BH₂NH₂]_n and [BH₂NMe₂]₂ and the tandem ammonia borane dehydrogenation–cyclohexene hydrogenation. DFT calculations on the ammonia borane dehydrogenation suggest that the process takes place by means of cis-κ²-PP-species, through four stages including: (i) Shimoi-type coordination of ammonia borane, (ii) homolytic addition of the coordinated H–B bond to afford a five-coordinate dihydride-boryl-rhodium(III) intermediate, (iii) reductive intramolecular proton transfer from the NH₃ group to one of the hydride ligands, and (iv) release of H₂ from the resulting square-planar hydride dihydrogen rhodium(I) intermediate.