Li Yafei, Pan Huifen, Lu Yanhua, Luo Yanshu, Dang Yan, Wang Yalan, Xia Shengwang, Li Yahong, Xia Yuanzhi
College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou 325035, China.
Dalton Trans. 2022 Mar 1;51(9):3616-3624. doi: 10.1039/d1dt03235f.
The push for environmentally benign and sustainable chemical processes has reinforced the demand to displace transition metals with cheap, nontoxic and naturally abundant metals. To fulfil this requirement, we endeavored to synthesize alkali- and alkaline earth-metal complexes and employ them as catalysts for organic transformations. Two lithium and one magnesium complexes, which are supported by pyridyl-pendanted unsymmetrical β-diketiminates, have been synthesized and characterized. They are formulated as [Li(L)] (1), [Li(L)] (2) and [Mg(L)]·0.5CH (3) (HL = N{-4-[(2,6-diisopropylphenylamino)pent-3-en-2-ylidene]-6-methyl}pyridin-2-amine and HL = -{4-[(2,6-diisopropylphenyl)imino]pent-2-en-2-yl}pyridin-2-amine). Complex 1 features two inequivalent Li(I) sites. One Li(I) center exhibits tetrahedral geometry, while the other Li(I) ion adopts a triangular coordination sphere. The catalytic activities of 1-3 toward the hydroboration of aldehydes and ketones by pinacolborane (HBpin) were investigated. Both dinuclear lithium complexes and homoleptic magnesium compound were found to be highly efficient catalysts for the hydroboration of aldehydes and ketones, affording the corresponding borate esters in good yields within a very short time. Synthetic application of the complexes was demonstrated by the gram-scale reduction of ketones a one-pot two step reaction with only 0.2 mol% loading of 2. Mechanistic details for the hydroboration were revealed by DFT calculations.
对环境友好且可持续的化学过程的推动，强化了用廉价、无毒且天然丰富的金属取代过渡金属的需求。为满足这一要求，我们致力于合成碱金属和碱土金属配合物，并将它们用作有机转化的催化剂。已经合成并表征了两种由吡啶基悬挂的不对称β-二酮亚胺支撑的锂配合物和一种镁配合物。它们的化学式分别为[Li(L)] (1)、[Li(L)] (2) 和 [Mg(L)]·0.5CH (3)（HL = N{-4-[(2,6-二异丙基苯基氨基)戊-3-烯-2-亚基]-6-甲基}吡啶-2-胺，HL = -{4-[(2,6-二异丙基苯基)亚氨基]戊-2-烯-2-基}吡啶-2-胺）。配合物1具有两个不等价的Li(I)位点。一个Li(I)中心呈现四面体几何构型，而另一个Li(I)离子采用三角配位球。研究了1-3对频哪醇硼烷(HBpin)对醛和酮的硼氢化反应的催化活性。发现双核锂配合物和均配镁化合物都是醛和酮硼氢化反应的高效催化剂，能在极短时间内以良好产率得到相应的硼酸酯。通过酮的克级还原反应（一种仅以0.2 mol%的2负载量进行的一锅两步反应）证明了这些配合物的合成应用。通过密度泛函理论(DFT)计算揭示了硼氢化反应的机理细节。
