Synthesis, structure and reaction chemistry of a nucleophilic aluminyl anion
Synthesis, structure and reaction chemistry of a nucleophilic aluminyl anion
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DOI：
10.1038/s41586-018-0037-y
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发表时间：
2018-05-03
期刊：
影响因子：
64.8
通讯作者：
Aldridge, Simon
中科院分区：
文献类型：
--
作者：
Hicks, Jamie;Vasko, Petra;Aldridge, Simon
铝化合物的反应性由它们的缺电子和亲电性决定;这些化合物是典型的刘易斯酸（电子对受体）。铝的主要工业作用和合成铝元素键的经典方法（例如，铝氢化和复分解）都是利用了AlR 3和AlCl 3（1，2）类型物质的缺电子性。尽管铝酸盐[AlR 4]（-）是众所周知的，但在成键取代反应中反转极性并使用铝试剂作为亲核配偶体的想法是前所未有的，这是因为与[NX 2]（-）、[CX 3]（-）和[BX 2]（-）类型的氮、碳和硼中心试剂类似的低价铝阴离子是未知的（3-5）。处于+1氧化态的铝化合物是已知的，但是相对于反离子化是化学上不稳定的。这种类型的化合物通常是低聚物（6-8），尽管也有报道（9，10）具有金属中心孤对电子的单体体系，如Al（NaClac）Dipp（其中（NaClac）（Dipp）=（NDippCR）（2）CH和R = Bu-t，Me; Dipp = 2，6-（Pr 2C 6 H3）-Pr-i）。已经观察到这些物质以及（eta（5）-C5 Me 5）Al与一系列刘易斯酸的配位（11-13），但是它们的主要反应模式涉及容易的氧化加成以生成Al（iii）物质（6- 8，14 -16）。本文报道了一种阴离子铝亲核试剂，二甲基氧杂蒽稳定的钾铝[K{Al（NON）}]（2）（NON = 4，5-双（2，6-二异丙基苯胺基）-2，7-二叔丁基-9，9-二甲基氧杂蒽）的合成、结构和反应化学。该物种在铝元素共价键的形成和苯的C-H氧化加成中表现出前所未有的反应性，这表明它可以在金属-碳和金属-金属键形成反应中找到进一步的用途。
The reactivity of aluminium compounds is dominated by their electron deficiency and consequent electrophilicity; these compounds are archetypal Lewis acids (electron-pair acceptors). The main industrial roles of aluminium, and classical methods of synthesizing aluminium-element bonds (for example, hydroalumination and metathesis), draw on the electron deficiency of species of the type AlR3 and AlCl3 (1,2). Whereas aluminates, [AlR4](-), are well known, the idea of reversing polarity and using an aluminium reagent as the nucleophilic partner in bondforming substitution reactions is unprecedented, owing to the fact that low-valent aluminium anions analogous to nitrogen-, carbon- and boron-centred reagents of the types [NX2](-), [CX3](-) and [BX2](-) are unknown(3-5). Aluminium compounds in the + 1 oxidation state are known, but are thermodynamically unstable with respect to disproportionation. Compounds of this type are typically oligomeric(6-8), although monomeric systems that possess a metal-centred lone pair, such as Al(Nacnac) Dipp (where (Nacnac)(Dipp) = (NDippCR)(2)CH and R = Bu-t, Me; Dipp = 2,6-(Pr2C6H3)-Pr-i), have also been reported(9,10). Coordination of these species, and also of (eta(5)-C5Me5)Al, to a range of Lewis acids has been observed(11-13), but their primary mode of reactivity involves facile oxidative addition to generate Al(iii) species(6-8,14-16). Here we report the synthesis, structure and reaction chemistry of an anionic aluminium(i) nucleophile, the dimethylxanthenestabilized potassium aluminyl [K{Al(NON)}](2) (NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene). This species displays unprecedented reactivity in the formation of aluminium-element covalent bonds and in the C-H oxidative addition of benzene, suggesting that it could find further use in both metal-carbon and metal-metal bond-forming reactions.