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首页> 外文期刊>Chemistry: A European journal >Chiral benzamidinate ligands in rare-earth-metal coordination chemistry
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Chiral benzamidinate ligands in rare-earth-metal coordination chemistry

机译：稀土金属配位化学中的手性苯甲酰胺基配体

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摘要

The treatment of the recently reported potassium salt (S)-N,N'-bis-(1- phenylethyl)benzamidinate ((S)-KPEBA) and its racemic isomer (rac-KPEBA) with anhydrous lanthanide trichlorides (Ln=Sm, Er, Yb, Lu) afforded mostly chiral complexes. The tris(amidinate) complex [{(S)-PEBA} _3Sm], bis(amidinate) complexes [{Ln(PEBA) _2(μ-Cl)} _2] (Ln=Sm, Er, Yb, Lu), and mono(amidinate) compounds [Ln(PEBA)(Cl) _2(thf) _n] (Ln=Sm, Yb, Lu) were isolated and structurally characterized. As a result of steric effects, the homoleptic 3:1 complexes of the smaller lanthanide atoms Yb and Lu were not accessible. Furthermore, chiral bis(amidinate)-amido complexes [{(S)-PEBA} _2Ln{N(SiMe _3) _2}] (Ln=Y, Lu) were synthesized by an amine-elimination reaction and salt metathesis. All of these chiral bis- and tris(amidinate) complexes had additional axial chirality and they all crystallized as diastereomerically pure compounds. By using rac-PEBA as a ligand, an achiral meso arrangement of the ligands was observed. The catalytic activities and enantioselectivities of [{(S)-PEBA} _2Ln{N(SiMe _3) _2}] (Ln=Y, Lu) were investigated in hydroamination/cyclization reactions. A clear dependence of the rate of reaction and enantioselectivity on the ionic radius was observed, which showed higher reaction rates but poorer enantioselectivities for the yttrium compound.
机译：最近报道的无水三氯化镧处理（S）-N，N'-双-（1-苯乙基）苯甲mid酸钾盐（S）-KPEBA及其外消旋异构体（rac-KPEBA） Er，Yb，Lu）主要提供手性配合物。三（酰胺基）络合物[{（S-PEBA} _3Sm]，双（酰胺基）络合物[{Ln（PEBA）_2（μ-Cl）} _2]（Ln = Sm，Er，Yb，Lu）和分离并合成了单酰胺基化合物[Ln（PEBA）（Cl）_2（thf）_n]（Ln = Sm，Yb，Lu）。由于空间效应，较小的镧系元素原子Yb和Lu的均质3：1络合物无法获得。此外，通过胺消除反应和盐复分解反应合成了手性双（酰胺基）-酰胺配合物[{（S）-PEBA} _2Ln {N（SiMe _3）_2}]（Ln = Y，Lu）。所有这些手性双-和三（酰胺基）配合物均具有额外的轴向手性，它们均以非对映体纯化合物的形式结晶。通过使用rac-PEBA作为配体，观察到配体的非手性内消旋排列。研究了[{（S）-PEBA} _2Ln {N（SiMe _3）_2}]（Ln = Y，Lu）在加氢胺化/环化反应中的催化活性和对映选择性。观察到反应速率和对映选择性对离子半径的明显依赖性，这显示出较高的反应速率但对钇化合物的对映选择性较差。

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