Zirconium-Catalyzed Amine Borane Dehydrocoupling and Transfer Hydrogenation

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• 作者：Karla A. Erickson ; John P. W. Stelmach ; Neil T. Mucha ; Rory Waterman
• 刊名：Organometallics
• 出版年：2015
• 出版时间：October 12, 2015
• 年：2015
• 卷：34
• 期：19
• 页码：4693-4699
• 全文大小：364K
• ISSN：1520-6041

文摘

魏⁵-(Me₃SiNCH₂CH₂)₂N(CH₂CH₂NSiMe₂CH₂)Zr (1) has been found to dehydrocouple amine borane substrates, RR鈥睳HBH₃ (R = R鈥?= Me; R = ^tBu, R鈥?= H; R = R鈥?= H), at low to moderate catalyst loadings (0.5鈥? mol %) and good to excellent conversions, forming mainly borazine and borazane products. Other zirconium catalysts, (N₃N)ZrX [(N₃N) = N(CH₂CH₂NSiMe₂CH₂)₃, X = NMe₂ (2), Cl (3), and O^tBu (4)], were found to exhibit comparable activities to that of 1. Compound 1 reacts with Me₂NHBH₃ to give (N₃N)Zr(NMe₂BH₃) (5), which was structurally characterized and features an 畏² B鈥揌 蟽-bond amido borane ligand. Because 5 is unstable with respect to borane loss to form 2, rather than 尾-hydrogen elimination, and 2鈥?b>4 do not exhibit X ligand loss during catalysis, dehydrogenation is hypothesized to proceed via an outer-sphere-type mechanism. This proposal is supported by the catalytic hydrogenation of alkenes by 2 using amine boranes as the sacrificial source of hydrogen.