ability to activate molecular hydrogen by reaction of silylium ion/phosphane Lewispairs is dominated by thermodynamic and steric factors. For a given silylium ion increasing proton affinity and increasing steric hindrance of the phosphane proved to be beneficial. Nevertheless, excessive steric hindrance leads to a breakdown of the dihydrogen-splitting activity of a silylium/phosphane Lewispair.
研究了一系列硅离子/膦路易斯对的反应性。硼酸三芳基甲硅烷基酯4 [B(C 6 F 5)4 ]与空间受阻的膦2形成中等稳定性的沮丧的路易斯对(FLP)。这些FLP中的某些能够在环境条件下裂解二氢。庞大的三烷基膦与三芳基甲硅烷基离子的结合可用于以甲硅烷基酰基phosph离子的形式隔离CO 2 12。通过甲硅烷基离子/膦路易斯对的反应来活化分子氢的能力主要由热力学和空间因素决定。对于给定的甲硅烷基离子,增加膦的质子亲和力和增加空间位阻被证明是有益的。然而,过大的空间位阻导致甲硅烷基/膦路易斯对的二氢分裂活性的破坏。
Photocatalytic Hydrodefluorination: Facile Access to Partially Fluorinated Aromatics
作者:Sameera M. Senaweera、Anuradha Singh、Jimmie D. Weaver
DOI:10.1021/ja500031m
日期:2014.2.26
science as well as the pharmaceutical and agrochemical industries and yet are often difficult to access. This Communication describes a photocatalytic hydrodefluorination approach which begins with easily accessible perfluoroarenes and selectively reduces the C-F bonds. The method allows facileaccess to a number of partially fluorinated arenes and takes place with unprecedented catalytic activity
catalyzed by bismuthinidenes, Phebox-Bi(I) and OMe-Phebox-Bi(I). Mechanistic studies on the elementary steps support a Bi(I)/Bi(III) redox cycle that comprises C(sp2)–F oxidative addition, F/H ligand metathesis, and C(sp2)–H reductive elimination. Isolation and characterization of a cationic Phebox-Bi(III)(4-tetrafluoropyridyl) triflate manifests the feasible oxidative addition of Phebox-Bi(I) into the
Hydrodefluorination of functionalized fluoroaromatics with triethylphosphine: a theoretical and experimental study
作者:Aldo A. Facundo、Alma Arévalo、Gabriela Fundora-Galano、Marcos Flores-Álamo、Emilio Orgaz、Juventino J. García
DOI:10.1039/c9nj00721k
日期:——
triethylphosphine as the sole defluorinating agent. That prompted us to evaluate the mechanistic proposal and in the light of these results, along with new experimental evidence, we have now modified the initial proposal. The new mechanism avoids the highly energetic β-elimination step of roughly 71 kcal mol−1 for hexafluorobenzene and pentafluoropyridine at 393.15 K, invoking the participation of water. The use
Synthesis and Lewis acidity of fluorophosphonium cations
作者:Christopher B. Caputo、Daniel Winkelhaus、Roman Dobrovetsky、Lindsay J. Hounjet、Douglas W. Stephan
DOI:10.1039/c5dt00217f
日期:——
A series of fluorophosphonium salts, [R3PF][X] (R = alkyl or aryl; X = FB(C6F5)3, [B(C6F5)4]), have been prepared by reactions of phosphine/borane frustrated Lewis pairs (FLPs) with XeF2 or difluorophosphoranes with [Et3Si][B(C6F5)4]. As the substituents bound to phosphorus become increasingly electron withdrawing, the corresponding fluorophosphonium salts are shown to be increasingly Lewis acidic
通过以下反应制备了一系列氟phosph盐[R 3 PF] [X](R =烷基或芳基; X = FB(C 6 F 5)3,[B(C 6 F 5)4 ])。 XeF 2使膦/硼烷受阻的路易斯对(FLP)或具有[Et 3 Si] [B(C 6 F 5)4 ]的二氟正膦。随着与磷结合的取代基变得越来越吸电子,相应的氟phosph盐显示出越来越路易斯酸性。还进行了计算以确定这些氟phosph阳离子的相对氟离子亲和力(FIA)。