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

Abstract

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 −78 °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 4–6 can also be prepared by stepwise reactions of H3L3I2 with n-BuLi in THF followed by reactions with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3. Stepwise reactions of H3L2I2 with n-BuLi in THF followed by treatment with [(Me3Si)2N]3RE(μ-Cl)Li(THF...