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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >N-Alkylfluorenyl-substituted N-heterocyclic carbenes as bimodal pincers
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N-Alkylfluorenyl-substituted N-heterocyclic carbenes as bimodal pincers

机译：N-烷基芴基取代的N-杂环卡宾作为双峰钳

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摘要

Two N-heterocyclic carbene precursors having their nitrogen atoms substituted by the expanded 9-ethyl-9-fluorenyl group, namely imidazolinium chloride 6 and imidazolium chloride 7, have been synthesized in high yields from fluorenone (1). The key intermediate of their syntheses is the new primary amine 9-ethyl-9-fluorenylamine (3), which was prepared in 75% yield. Both salts were readily converted into the corresponding PEPPSI-type palladium complexes, 8 and 9 (PEPPSI: pyridine-enhanced precatalyst preparation stabilisation and initiation). Despite rotational freedom of the ethylfluorenyl moieties about the N-C(fluorenyl) bond in their cationic precursors, the carbene ligands of the Pd(II)-complexes 8 and 9 both behave as bimodal pincers in solution and in the solid state, the resulting confinement being essentially due to (weak) attractive anagostic interactions between the CH2(fluorenyl) groups and the metal centre. Unlike in 8 and 9, there was no indication for similar anagostic interactions in the imidazolylidene chlorosilver complex 11, which could be obtained from 7. In the solid state, however, 11 adopts a remarkable "open sandwich" structure, with the two alkylfluorenilidene planes eta(2)-bonded to the silver, this constituting a further bimodal pincer-type bonding mode of this ligand class. Complexes 8 and 9 were assessed in Suzuki-Miyaura cross-coupling reactions. The imidazolylidene complex 9 displayed high activity towards unencumbered aryl chlorides. Its activity is comparable to that of the previously reported, highly efficient benzimidazolylidene analogue 10.
机译：由芴酮（1）以高收率合成了两个氮原子被膨胀的9-乙基-9-芴基取代的N-杂环卡宾前体，即氯化咪唑啉鎓盐6和氯化咪唑鎓盐7。它们合成的关键中间体是新的伯胺9-乙基-9-芴基胺（3），其产率为75％。两种盐都容易转变成相应的PEPPSI型钯配合物8和9（PEPPSI：吡啶增强的预催化剂制备物的稳定和引发）。尽管在其阳离子前体中乙基芴基部分绕NC（芴基）键具有旋转自由度，但Pd（II）配合物8和9的卡宾配体在溶液和固态下均充当双峰钳子，因此限制基本上是由于CH2（芴基）基团与金属中心之间的（弱）吸引性的无电相互作用。与8和9不同，在咪唑基氯银络合物11中没有类似反应的迹象，可以从7中获得。然而，在固态下，11具有显着的“开放三明治”结构，具有两个烷基芴基平面eta（2）-键合至银，这构成了该配体类别的另一双峰钳式键合模式。在铃木-宫浦交叉偶联反应中评估复合物8和9。咪唑基亚烷基络合物9显示出对不受阻碍的芳基氯的高活性。其活性与先前报道的高效苯并咪唑基亚苄基类似物10相当。

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