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首页> 外文期刊>Chemistry: A European journal >Synthesis and characterization of [Cu(NHC)(2)]X complexes: Catalytic and mechanistic studies of hydrosilylation reactions
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Synthesis and characterization of [Cu(NHC)(2)]X complexes: Catalytic and mechanistic studies of hydrosilylation reactions

机译：[Cu（NHC）（2）] X配合物的合成和表征：氢化硅烷化反应的催化和机理研究

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摘要

The preparation of two series of [Cu(NHC)(2)]X complexes (NHC=N-heterocyclic carbene, X=PF6 or BF4) in high yields from readily available materials is reported. These complexes have been spectroscopically and structurally characterized. The activity of these cationic bis-NHC complexes in the hydrosilylation of ketones was examined, and both the ligand and the counterion showed a significant influence on the catalytic performance. Moreover, when compared with related [Cu(NHC)]-based systems, these cationic complexes proved to be more efficient under similar reaction conditions. ne activation step of [Cu(NHC),]X precatalysts towards hydrosilylation was investigated by means of H-1 NMR spectroscopy. Notably, it was shown that one of the N,N'-bis(2,6-di-isopropylphenyl)imidazol-2-ylidene (IPr) ligands in [Cu(IPr)(2)]BF4 is displaced by tBuO(-) in the presence of NaOtBu, producing the neutral [Cu-(IPr)(OtBu)]. This copper alkoxide is known to be a direct precursor of an NHC-copper hydride, the actual active species in this transformation. Furthermore, reagent loading and counterion effects have been rationalized in light of the species formed during the reaction.
机译：据报道，从易得的材料中以高收率制备了两个系列的[Cu（NHC）（2）] X络合物（NHC = N-杂环卡宾，X = PF6或BF4）。这些配合物已经在光谱和结构上进行了表征。检查了这些阳离子双-NHC络合物在酮的氢化硅烷化中的活性，并且配体和抗衡离子均显示出对催化性能的显着影响。此外，与相关的基于[Cu（NHC）]的体系相比，这些阳离子配合物在相似的反应条件下被证明更有效。通过H-1 NMR光谱研究了[Cu（NHC），] X预催化剂向氢化硅烷化的活化步骤。值得注意的是，已表明[Cu（IPr）（2）] BF4中的N，N'-双（2,6-二异丙基苯基）咪唑-2-亚烷基（IPr）配体之一被tBuO（- ）在NaOtBu存在下，生成中性[Cu-（IPr）（OtBu）]。已知该醇铜是NHC-铜氢化物的直接前体，NHC-铜氢化物是该转化中的实际活性物质。此外，已经根据反应过程中形成的物质合理化了试剂的装载量和抗衡离子的作用。

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