Synthesis of Bis(NHC)-Based CNC-Pincer Rare-Earth-Metal Amido Complexes and Their Application for the Hydrophosphination of Heterocumulenes

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• 作者：Xiaoxia Gu ; Lijun Zhang ; Xiancui Zhu ; Shaowu Wang ; Shuangliu Zhou ; Yun Wei ; Guangchao Zhang ; Xiaolong Mu ; Zeming Huang ; Dongjing Hong ; Feng Zhang
• 刊名：Organometallics
• 出版年：2015
• 出版时间：September 28, 2015
• 年：2015
• 卷：34
• 期：18
• 页码：4553-4559
• 全文大小：421K
• ISSN：1520-6041

文摘

The bis(NHC) (NHC = N-heterocyclic carbene)-based CNC-pincer rare-earth-metal amido complexes LRE[N(SiMe₃)₂]₂ (L = 4-CH₃-2-{R-[N(CH)₂CN]}C₆H₃]₂N; L², R = CH₃; L³, R = CH(CH₃)₂) were synthesized and characterized, and their catalytic activities toward hydrophosphination of heterocumulenes were developed. Reactions of bis[2-(3-methylimidazolium)-4-methylphenyl]amine diiodide (H₃L²I₂) or bis[2-(3-isopropylimidazolium)-4-methylphenyl]amine diiodide (H₃L³I₂) with 5 equiv of NaN(SiMe₃)₂ followed by treatment with 1 equiv of RECl₃ in THF at 鈭?8 掳C afforded the bis(NHC)-based CNC-pincer rare-earth-metal amido complexes LRE[N(SiMe₃)₂]₂ (L² = [4-CH₃-2-{CH₃-[N(CH)₂CN]}C₆H₃]₂N, RE = Y (1), Eu (2), Er (3); L³ = [4-CH₃-2-{(CH₃)₂CH-[N(CH)₂CN]}C₆H₃]₂N, RE = Y (4), Er (5), Yb (6)). Complexes 4鈥?b>6 can also be prepared by stepwise reactions of H₃L³I₂ with n-BuLi in THF followed by reactions with [(Me₃Si)₂N]₃RE(渭-Cl)Li(THF)₃. Stepwise reactions of H₃L²I₂ with n-BuLi in THF followed by treatment with [(Me₃Si)₂N]₃RE(渭-Cl)Li(THF)₃ generated the bis(NHC)-based CNC-pincer rare-earth-metal amido complexes L²RE[N(SiMe₃)₂]₂ (RE = Y (1), Er (3)) together with the fused-heterocyclic compound 3,8,9-trimethyl-8a,9-dihydro-8H-benzo[4,5]imidazo[2鈥?1鈥?2,3]imidazo[1,2-a]imidazo[2,1-c]quinoxaline (7), which formed through carbene C鈥揅 and C鈥揘 coupling. Attempts to prepare complexes of the type LRE[N(SiMe₃)₂]₂ by reaction of H₃L³I₂ with [(Me₃Si)₂N]₃Yb(渭-Cl)Li(THF)₃ in THF, however, afforded mixed complexes of the bis(NHC)-based CNC-pincer ytterbium complex L³Yb[N(SiMe₃)₂]₂ (6) and the unexpected bis(NHC)-based CNC-pincer monoamido ytterbium iodide L³YbI[N(SiMe₃)₂] (8). Investigation of the catalytic activity of complexes 1鈥?b>6 and 8 indicated that all complexes displayed high activity toward the addition of the phosphine P鈥揌 bond to heterocumulenes, producing the corresponding phosphaguanidines, phosphaureas, and phosphathioureas, which represents the first example of bis(NHC)-based CNC-pincer type rare-earth-metal amido complexes as catalysts for the catalytic addition of the phosphine P鈥揌 bond to heterocumulenes with high efficiency in the presence of a low catalyst loading at room temperature.