Xu Xiaoping, Zhang Zhongjian, Yao Yingming, Zhang Yong, Shen Qi
Key Laboratory of Organic Synthesis of Jiangsu Province, Department of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215006, P.R. China.
Inorg Chem. 2007 Oct 29;46(22):9379-88. doi: 10.1021/ic701148z. Epub 2007 Sep 19.
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(mu-Cl)(THF)]2 (TMS = SiMe3) afforded the desired bridged bis(phenolate) lanthanide chlorides [(MBMP)Ln(mu-Cl)(THF)2]2 [Ln = Nd (1), Yb (2)] in high isolated yields. These lanthanide 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) lanthanide amido complexes (MBMP)LnN(TMS)22 [Ln = Nd (3), Yb (4)] in high yields. Whereas the reactions of 1 and 2 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 and 6 can also be conveniently synthesized in high yields by the direct reactions of MBMPH2 with [Ln{N(TMS)2}2(mu-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 carbodiimide into the Ln-N bond of neutral lanthanide amido complexes 3 and 4 gave the anticipated bis(phenolate) lanthanide guanidinate complexes [(mu-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 unexpected ligand-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) lanthanide amides showed higher catalytic activity for the polymerization of epsilon-caprolactone than the neutral ones. All of the complexes were characterized with elemental analysis and IR spectra, and the definitive molecular structures of 1-3 and 5-9 were provided by single-crystal X-ray analyses.
通过一般的复分解反应合成了一系列中性和阴离子型双（酚盐）镧系酰胺，并对其反应活性进行了探索。MBMPH2（MBMP = 2,2'-亚甲基双（6-叔丁基-4-甲基酚盐））与[Ln{N(TMS)2}2(μ-Cl)(THF)]2（TMS = SiMe3）的质子解配体交换反应以高分离产率得到了所需的桥联双（酚盐）镧系氯化物[(MBMP)Ln(μ-Cl)(THF)2]2 [Ln = Nd (1)，Yb (2)]。发现这些镧系氯化物是合成相应镧系衍生物的有用前体。1和2与2当量的NaN(TMS)2在THF中反应，高产率地生成了预期的中性双（酚盐）镧系酰胺配合物(MBMP)LnN(TMS)22 [Ln = Nd (3)，Yb (4)]。而1和2与LiN(TMS)2以1:4的摩尔比反应，以高分离产率得到了阴离子型双（酚盐）镧系酰胺，为离散离子对配合物[Li(THF)4][(MBMP)Ln{N(TMS)2}2] [Ln = Nd (5)，Yb (6)]。进一步研究表明，5和6也可以通过MBMPH2与[Ln{N(TMS)2}2(μ-Cl)(THF)]2以2:1的摩尔比直接反应，然后与4当量的正丁基锂方便地高产率合成。对中性和阴离子型双（酚盐）镧系酰胺的反应活性进行了比较研究。发现碳二亚胺插入中性镧系酰胺配合物3和4的Ln-N键的反应分别高产率地得到了预期的双（酚盐）镧系胍基配合物[(μ-O-MBMP)Nd{(iPrN)2CN(TMS)2}]2 (7)和(MBMP)Yb[(iPrN)2CN(TMS)2] (8)，而碳二亚胺与阴离子酰胺配合物5的类似反应提供了意外的配体重新分布产物，并且最终分离出了纯离子对双（酚盐）钕配合物[Li(DME)2(THF)][(MBMP)2Nd(THF)2] (9)作为产物之一。此外，阴离子型双（酚盐）镧系酰胺对ε-己内酯聚合的催化活性高于中性的。所有配合物均通过元素分析和红外光谱进行了表征，并且通过单晶X射线分析提供了1 - 3和5 - 9的确定分子结构。
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