Controlled Syntheses, Characterization, and Reactivity of Neutral and Anionic Lanthanide Amides Supported by Methylene-Linked Bis(phenolate) Ligands

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• 作者：Xiaoping Xu ; Zhongjian Zhang ; Yingming Yao ; Yong Zhang ; Qi Shen
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：October 29, 2007
• 年：2007
• 卷：46
• 期：22
• 页码：9379 - 9388
• 全文大小：200K
• 年卷期：v.46,no.22(October 29, 2007)
• ISSN：1520-510X

文摘

A series of neutral and anionic bis(phenolate) lanthanide amides were synthesized by general metathesis reactions,and their reactivity was explored. Protolytic ligand exchange reactions of MBMPH₂ (MBMP = 2,2'-methylene bis(6-tert-butyl-4-methyl-phenolate)) with [Ln{N(TMS)₂}₂(-Cl)(THF)]₂ (TMS = SiMe₃) afforded the desired bridgedbis(phenolate) lanthanide chlorides [(MBMP)Ln(-Cl)(THF)₂]₂ [Ln = Nd (1), Yb (2)] in high isolated yields. Theselanthanide chlorides were found to be useful precursors for the synthesis of the corresponding lanthanide derivatives.Reactions of 1 and 2 with 2 equiv of NaN(TMS)₂ in THF produced the expected neutral bis(phenolate) lanthanideamido complexes (MBMP)Ln[N(TMS)₂](THF)₂ [Ln = Nd (3), Yb (4)] in high yields. Whereas the reactions of 1 and2 with LiN(TMS)₂ in a 1:4 molar ratio gave the anionic bis(phenolate) lanthanide amides as discrete ion-pair complexes[Li(THF)₄][(MBMP)Ln{N(TMS)₂}₂] [Ln = Nd (5), Yb (6)] in high isolated yields. Further study revealed that 5 and6 can also be conveniently synthesized in high yields by the direct reactions of MBMPH₂ with [Ln{N(TMS)₂}₂(-Cl)(THF)]₂ in a 2:1 molar ratio, and then with 4 equiv of ⁿBuLi. The reactivity of the neutral and anionic bis(phenolate) lanthanide amides was comparatively investigated. It was found that the insertion reactions of carbodiimideinto the Ln-N bond of neutral lanthanide amido complexes 3 and 4 gave the anticipated bis(phenolate) lanthanideguanidinate complexes [(-O-MBMP)Nd{(ⁱPrN)₂CN(TMS)₂}]₂ (7) and (MBMP)Yb[(ⁱPrN)₂CN(TMS)₂] (8), respectively,in high yields, whereas the similar reaction of carbodiimide with anionic amido complex 5 provided the unexpectedligand-redistributed products, and the homoleptic ion-pair bis(phenolate) neodymium complex [Li(DME)₂(THF)][(MBMP)₂Nd(THF)₂] (9) was finally isolated as one of the products. Furthermore, the anionic bis(phenolate) lanthanideamides showed higher catalytic activity for the polymerization of -caprolactone than the neutral ones. All of thecomplexes were characterized with elemental analysis and IR spectra, and the definitive molecular structures of1-3 and 5-9 were provided by single-crystal X-ray analyses.