Hydrogen Isotope Exchange with Iridium(I) Complexes Supported by Phosphine-Imidazolin-2-imine P,N Ligands

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• 作者：Kristof Jess ; Volker Derdau ; Remo Weck ; Jens Atzrodt ; Matthias Freytag ; Peter G. Jones and Matthias Tamm
• 刊名：Advanced Synthesis & Catalysis
• 出版年：2017
• 出版时间：February 20, 2017
• 年：2017
• 卷：359
• 期：4
• 页码：629-638
• 全文大小：1179K
• ISSN：1615-4169

文摘

Phenylene-bridged hybrid phosphine-imidazolin-2-imine ^RP,N^R′ ligands (R=Ph, Cy, i-Pr, t-Bu; R′=Me, i-Pr) were prepared from 1,2-dibromobenzene by palladium-catalyzed C–N coupling with 1,3,4,5-tetramethylimidazolin-2-imine or 1,3-diisopropyl-4,5-dimethylimidazolin-2-imine, followed by lithiation with tert-butyllithium and reaction with the chlorophosphines (R₂PCl). Their reaction with the dimeric iridium complex [Ir(cod)Cl]₂ (cod=1,5-cyclooctadiene) and subsequent anion exchange with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF₂₄) or potassium hexafluorophosphate (KPF₆) afforded iridium complexes of the type [(^RP,N^R′)Ir(cod)]BArF₂₄ or [(^RP,N^R′)Ir(cod)]PF₆, respectively. The latter PF₆ salts were structurally characterized, revealing short Ir—N bonds as an indication of electron-rich nitrogen donor atoms. The former complexes were tested for their applicability in catalytic H/D exchange. In particular, the complex with the ligand ^t-BuP,N^Me showed remarkable performance in H/D exchange with a broad range of aromatic substrates, including ketones, amides, esters, heterocycles and nitro compounds, and also promoted H/D exchange at aromatic Boc-protected amines, benzylamines and methoxy derivatives.