Research News, Oct. 17th, 2012

Published on 2012-10-17

Rare-Earth Metal Tris(trimethylsilylmethyl) Anionic Complexes Bearing One 1-Phenyl-2,3,4,5-tetrapropylcyclopentadienyl Ligand: Synthesis, Structural Characterization and Application

Ling Xu, Zitao Wang, Wen-Xiong Zhang,* and Zhenfeng Xi*

Inorg. Chem. 2012,DOI: 10.1021/ic-2012-018369.

It is of great interest and importance to explore the synthesis and application of the isolable and soluble half-sandwich rare-earth anionic alkyl complexes. It will become a promising field if the reactivity of such anionic alkyl complexes is much closer to or better than that of neutral complexes because of their easy availability.

This paper reports the first synthesis of rare-earth metal tri(trimethylsilylmethyl) anionic complexes bearing one 1-phenyl-2,3,4,5-tetrapropylcyclopentadienyl ligand [Cp4PrPhLn(CH2SiMe3)3][Li(thf)n(OEt2)4-n] (1-Ln: Y, Er, Tm and Lu: n = 3, Ho: n = 4), whose structures are fully characterised. These soluble anionic compounds show good reactivity in the stoichiometric reaction with dibenzoylmethane. More importantly, they can serve as excellent catalyst precursors for the addition of ArRNH or ArAr’NH to carbodiimides yielding efficiently guanidines. Previously, such addition cannot be accomplished efficiently by the reported catalysts. Our results show clearly the reactivities of anionic trialkyl precursors are comparable with the corresponding neutral alkyl complex, but exhibit better catalytic activity than the known catalysts.

背景介紹

稀土金屬烷基化合物的設計、合成、結構鑒定及催化應用在稀土金屬導向有機合成化學和聚合物化學領域中有重要的應用前景，一直是金屬有機化學的一個前沿且具挑戰性的研究領域。中性的單茂稀土金屬雙烷基化合物的合成主要集中在Sc，Y，Gd-Lu等金屬配合物，它們在聚合反應中有廣泛的應用前景，然而，相應的單茂稀土金屬多烷基ate配合物的合成，由于其溶解度較低，它們的合成和應用較少受到人們的關注。

本研究室經過幾年的努力，利用自己發展的1-苯基-2,3,4,5-四丙基環戊二烯配體(Zhao, C.; Li, P.; Cao, X.; Xi, Z. Chem. –Eur. J. 2002, 8, 4292; Xi, Z.; Li, P. Angew. Chem. Int. Ed. 2000, 39, 2950.)，成功合成了一系列易溶的單Cp4PrPh稀土金屬三烷基ate配合物。通過與二酮（DBM）反應，合成了單Cp4PrPh雙二酮化合物，并通過單晶鑒定了其結構。盡管已有較多的催化劑種類能實現胺對碳二亞胺的加成反應，但還沒有催化劑能實現ArRNH 或ArAr’NH對碳二亞胺的加成。此類ate配合物具有很好的催化活性，是第一個通用的催化劑，高效實現不同胺對碳二亞胺的催化加成反應。