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Facile and systematic access to the least-coordinating WCA [(RFO)3Al–F–Al(ORF)3]− and its more Lewis-basic brother [F–Al(ORF)3]− (RF = C(CF3)3)†
Chemical Science ( IF 7.6 ) Pub Date : 2018-08-01 00:00:00 , DOI: 10.1039/c8sc02591f
Arthur Martens 1 , Philippe Weis 1 , Michael Christian Krummer 1 , Marvin Kreuzer 1 , Andreas Meierhöfer 1 , Stefan C Meier 1 , Jan Bohnenberger 1 , Harald Scherer 1 , Ian Riddlestone 1 , Ingo Krossing 1
Affiliation  

By reaction of the Lewis acid Me3Si–F–Al(ORF)3 with a series of [PF6] salts, gaseous PF5 and Me3Si–F are liberated and salts of the anion [F–Al(ORF)3] ([f–al]; RF = C(CF3)3) can be obtained. By addition of another equivalent of Me3Si–F–Al(ORF)3 to [f–al], gaseous Me3Si–F is released and salts of the least coordinating anion [(RFO)3Al–F–Al(ORF)3] ([al–f–al]) are formed. Both procedures work for a series of synthetically useful cations including Ag+, [NO]+, [Ph3C]+ and in very clean reactions with 5 g batch sizes giving excellent yields typically exceeding 90%. In addition, the synthesis of Me3Si–F–Al(ORF)3 has been optimized and scaled up to 85 g batches in an one-pot procedure. These anions could previously only be obtained by difficult to control decomposition reactions of [Al(ORF)4] or by halide abstraction reactions with Me3Si–F–Al(ORF)3, generating relatively large countercations that are unsuited for further use as universal starting materials. Especially [al–f–al] is of interest for the stabilization of reactive cations, since it is even weaker coordinating than [Al(ORF)4] and more stable against strong electrophiles. This bridged anion can be seen as an adduct of [f–al] and Al(ORF)3. Thus, it is similarly Lewis acidic as BF3 and eventually reacts with nucleophiles (Nu) from the reaction environment to yield Nu–Al(ORF)3 and [f–al]. This prevents working with [al–f–al] salts in ethereal or other donor solvents. By contrast, the [f–al] anion is no longer Lewis acidic and may therefore be used for reactions involving stronger nucleophiles than the [al–f–al] anion can withstand. Subsequently it may be transformed into the [al–f–al] salt by simple addition of one equivalent of Me3Si–F–Al(ORF)3.

中文翻译:


轻松系统地获得最不配位的 WCA [(RFO)3Al–F–Al(ORF)3]− 及其更路易斯基本的兄弟 [F–Al(ORF)3]− (RF = C(CF3)3 )†



通过路易斯酸 Me 3 Si–F–Al(OR F ) 3与一系列 [PF 6 ] -盐的反应,释放出气态 PF 5和 Me 3 Si–F 以及阴离子 [F–Al(可以得到OR F ) 3 ] ([f–al] ; RF = C(CF 3 ) 3 )。通过将另一当量的 Me 3 Si–F–Al(OR F ) 3添加到 [f–al] -中,释放气态 Me 3 Si–F 并释放出最少配位阴离子的盐 [(R F O) 3 Al–形成 F–Al(OR F ) 3 ] - ([al–f–al] - )。两种程序均适用于一系列合成有用的阳离子,包括 Ag + 、[NO] + 、[Ph 3 C] + ,并且在非常干净的反应中,批量大小为 5 g,产率通常超过 90%。 此外,Me 3 Si–F–Al(OR F ) 3的合成已得到优化,并在一锅法中放大至 85 g 批次。这些阴离子以前只能通过难以控制的 [Al(OR F ) 4 ] -分解反应或通过与 Me 3 Si–F–Al(OR F ) 3的卤化物提取反应来获得,产生相对较大的抗衡阳离子,不适合进一步用作通用起始材料。特别是 [al–f–al] -对于反应性阳离子的稳定很有意义,因为它的配位性比 [Al(OR F ) 4 ] -更弱,并且对强亲电子试剂更稳定。这种桥接阴离子可以看作是 [f–al] -和 Al(OR F ) 3的加合物。因此,它与 BF 3类似,呈路易斯酸性,最终与反应环境中的亲核试剂 (Nu) 反应,生成 Nu–Al(OR F ) 3和 [f–al] - 。这可以防止在乙醚或其他供体溶剂中使用 [al–f–al] 盐。 相比之下,[f-al] -阴离子不再是路易斯酸性,因此可用于涉及比[al-f-al] -阴离子能承受的更强亲核试剂的反应。随后,通过简单添加一当量的 Me 3 Si–F–Al(OR F ) 3 ,可以将其转化为 [al–f–al] -盐。
更新日期:2018-08-01
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