Iridacycles as Catalysts for the Autotandem Conversion of Nitriles into Amines by Hydrosilylation: Experimental Investigation and Scope,Organometallics

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Iridacycles as Catalysts for the Autotandem Conversion of Nitriles into Amines by Hydrosilylation: Experimental Investigation and Scope
Organometallics ( IF 2.5 ) Pub Date : 2017-12-04 00:00:00 , DOI: 10.1021/acs.organomet.7b00749
Mustapha Hamdaoui ₁ , Camille Desrousseaux ₁ , Houda Habbita ₁ , Jean-Pierre Djukic ₁

Affiliation

The set of iridacycles [{C,N}Cp*Ir^III-Cl] ({C,N} = benzo[h]quinoline, dibenzo[f,h]quinoline) containing the (pentamethylcyclopentadienyl)iridium(III) unit were synthesized and derivatized into cations [{C,N}Cp*Ir-NCMe]⁺ associated with BArF-type anions. The latter salts were benchmarked for their potential catalytic properties toward HSiEt₃ in a H₂-releasing test reaction. The best-performing BArF-type salts demonstrated the capability to promote with a low catalytic load of ca. 0.5–1 mol % the autotandem hydrosilylation of acetonitrile, propionitrile, and a series of arylnitrile substrates. Mechanistic investigations confirmed the preliminary formation of a silane–iridacycle adduct by electrophilic and heterolytic activation of the Si–H bond. The molecular structure of a new example of such an adduct was resolved by X-ray diffraction analysis. Theoretical considerations support a donor–acceptor [{C,N}Cp*Ir^III-H]→[SiEt₃]⁺ ({C,N} = benzo[h]quinolinyl) formulation where the cationic silyl moiety acting as a Z ligand binds both Ir and H centers. Under the conditions of the catalysis, the latter adduct is assumed to transfer readily the electrophilic [SiEt₃]⁺ moiety to the nucleophilic nitrile substrate to form a N-silylnitrilium cation and the neutral [{C,N}Cp*Ir-H]. The latter reduces the N-silylnitrilium into the corresponding N-silylimine, which undergoes further N-silylation and reduction to yield the final N,N-disilylamine. Under optimal conditions of low catalyst load (70 °C, 0.5 mol %) the autotandem hydrosilylation of arylnitriles produces the silylated amines in yields >80% in 24 h.

中文翻译：

Iridacycles作为通过氢化硅烷化将腈自动串联转化为胺的催化剂：实验研究和范围

合成了含有（五甲基环戊二烯基）铱（III）单元的一组iridacycles [{C，N} Cp * Ir ^III -Cl]（{C，N} =苯并[ h ]喹啉，二苯并[ f，h ]喹啉）并衍生为与BArF型阴离子缔合的阳离子[{C，N} Cp * Ir-NCMe] ⁺。后者的盐因其在H _2中对HSiEt ₃的潜在催化性能而进行了基准测试-释放测试反应。表现最佳的BArF型盐显示出能够以低的催化负载量（大约）促进反应的能力。乙腈，丙腈和一系列芳腈底物的自动串联氢化硅烷化为0.5–1 mol％。机理研究证实，Si-H键的亲电和杂合活化可初步形成硅烷-铱环加合物。通过X射线衍射分析解析了这种加合物的新实例的分子结构。理论上的考虑支持了施主-受主[{C，N} Cp * Ir ^III -H]→[SiEt ₃ ] ⁺（{C，N} =苯并[ h ]喹啉基）的配方，其中阳离子甲硅烷基部分充当Z配体结合Ir和H中心。在催化条件下，假定后者加成物易于将亲电子[SiEt ₃ ] ⁺部分转移至亲核腈底物上，形成N-甲硅烷基氮阳离子和中性[{C，N} Cp * Ir-H] 。后者将N-甲硅烷基腈还原成相应的N-甲硅烷基亚胺，其进一步进行N-甲硅烷基化和还原以产生最终的N，N-二甲硅烷基胺。在低催化剂负载（70°C，0.5 mol％）的最佳条件下，芳基腈的串联氢化硅烷化反应会在24小时内产生甲硅烷基化胺，收率> 80％。

更新日期：2017-12-04

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