A palladium pre-catalyst, [Pd(PCy₃)₂] is reported for the efficient and selective C–F alumination of fluorobenzenes with the aluminium(I) reagent [{(ArNCMe)₂CH}Al] (1, Ar = 2,6-di-iso-propylphenyl). The catalytic protocol results in the transformation of sp² C–F bonds to sp² C–Al bonds and provides a route to reactive organoaluminium complexes (2a–h) from fluorocarbons. The catalyst is highly active. Reactions proceed within 5 minutes at 25 °C (and at appreciable rates at even −50 °C) and the scope includes low-fluorine-content substrates such as fluorobenzene, difluorobenzenes and trifluorobenzenes. The reaction proceeds with complete chemoselectivity (C–F vs. C–H) and high regioselectivities (>90% for C–F bonds adjacent to the most acidic C–H sites). The heterometallic complex [Pd(PCy₃)(1)₂] was shown to be catalytically competent. Catalytic C–F alumination proceeds with a KIE of 1.1–1.3. DFT calculations have been used to model potential mechanisms for C–F bond activation. These calculations suggest that two competing mechanisms may be in operation. Pathway 1 involves a ligand-assisted oxidative addition to [Pd(1)₂] and leads directly to the product. Pathway 2 involves a stepwise C–H → C–F functionalisation mechanism in which the C–H bond is broken and reformed along the reaction coordinate, guiding the catalyst to an adjacent C–F site. This second mechanism explains the experimentally observed regioselectivity. Experimental support for this C–H activation playing a key role in C–F alumination was obtained by employing [{(MesNCMe)₂CH}AlH₂] (3, Mes = 2,4,6-tri-methylphenyl) as a reagent in place of 1. In this instance, the kinetic C–H alumination intermediate could be isolated. Under catalytic conditions this intermediate converts to the thermodynamic C–F alumination product.

中文翻译：

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钯催化氟代CF的络合：机械多样性和选择性的起源

据报道，钯前催化剂[Pd（PCy ₃）₂ ]用于铝（I）试剂[{（ArNCMe）₂ CH} Al]（1，Ar = 2 ，6-二异丙基苯基）。催化方案导致sp ² C–F键转变为sp ² C–Al键，并为反应性有机铝络合物（2a–h）。该催化剂是高活性的。反应在25°C下5分钟内进行（甚至在-50°C时也有明显的速率），反应范围包括低氟含量的底物，例如氟苯，二氟苯和三氟苯。反应进行时具有完全的化学选择性（CF vs. CH）和高区域选择性（与最酸性的CH位相邻的CF键> 90％）。杂金属配合物[Pd（PCy ₃）（1）₂被证明具有催化能力。催化CF光化的KIE为1.1-1.3。DFT计算已用于为CF键活化的潜在机制建模。这些计算表明可能存在两种竞争机制。途径1涉及[Pd（1）₂ ]的配体辅助氧化添加，并直接导致产物。途径2涉及逐步的C–H→C–F官能化机制，其中C–H键沿着反应坐标被破坏并重新形成，将催化剂引导至相邻的C–F位置。第二种机制解释了实验观察到的区域选择性。通过使用[{（MesNCMe）₂ CH} AlH获得了对这种在CHF中起关键作用的CHH活化的实验支持。₂ ]（ 3，Mes = 2,4,6-三甲基苯基）代替1。在这种情况下，可以分离出动力学C–H的铝中间体。在催化条件下，该中间体转化为热力学C-F铝化产物。