1603-99-2Relevant articles and documents
CO2 activation with bulky neutral and cationic phenoxyalanes
Wehmschulte, Rudolf J.,Saleh, Mahmoud,Powell, Douglas R.
, p. 6812 - 6819 (2013)
The sterically crowded aluminum diphenolate (2,6-Mes2C 6H3O)2AlEt (2; Mes =2,4,6-Me3C 6H2-) was converted into the ionic species [(2,6-Mes 2C6H3O)2Al]+[CHB 11Cl11]- (6) by ethide abstraction with the silylium salt [Et3Si][CHB11Cl11] or by a combination of β-hydride abstraction and concomitant ethylene elimination with the trityl salt [Ph3C][CHB11Cl11]. Compound 6 consists of solvent-separated ions, and the cation features very short Al···C contacts involving the flanking mesityl groups, leading to an overall distorted-tetrahedral coordination geometry around the aluminum center. Analogous reactions with the diphenolate (2,6-tBu 2-4-MeC6H2O)2AlEt (1) led to tert-butyl transfer to the benzene solvent to afford tert-butylbenzene as the main product. A 1:1 mixture of the triphenolate (2,6-Ph2C 6H3O)3Al and tri-tert-butylphosphine forms a frustrated Lewis pair, which reacts with CO2 at room temperature to give the compound (2,6-Ph2C6H3O) 3AlOC(O)Pt-Bu3 (8). The high Lewis acidity of 6 catalyzes the scrambling of the subsituents of Et3SiH at room temperature to give Et4Si, Et2SiH2, and EtSiH3 and also the reduction of CO2 to d5-toluene (C 6D5CH3) and CH4 at 82 C in d 6-benzene solution.
An alternative route to electrophilic substitution. 2. Aromatic alkylation in the ion neutral complexes formed upon addition of gaseous arenium ions to olefins
Aschi, Massimiliano,Attinà, Marina,Cacace, Fulvio
, p. 12832 - 12839 (1995)
The joint application of mass spectrometric and radiolytic techniques has allowed demonstration of an alternative route to electrophilic aromatic substitution operative in the gas phase, where the Wheland intermediate is formed within the ion-neutral complex (INC) formed upon addition of an arenium ion to an olefin. Experiments involving several representative pairs of arenium ions XC6H6+ (X = H, CH3, CF3) and olefins (C3H6, iC4H8, cC5H8) have provided conclusive evidence for the operation of the above reaction sequence and hence for the occurrence of intracomplex alkylation. The peculiar mechanistic features of the reaction fit a model that identifies the relative basicity of the arene and of the olefin associated in any given INC as the key kinetic factor. The model accounts for the seemingly paradoxical observation that the alkylated products from less activated substrates are formed at relatively higher rates and for the occurrence of consecutive alkylation steps, yielding polyalkylated products of the less activated substrates. The relevance of the work to the theory of the aromatic substitution as a new entry into the reaction manifold of Friedel-Crafts alkylation and to gas-phase ion chemistry, as an irrefutable demonstration of the kinetic role of INCs is briefly discussed.
Heterolytic Oxidative Addition of sp2and sp3C-H Bonds by Metal-Ligand Cooperation with an Electron-Deficient Cyclopentadienone Iridium Complex
Higashi, Takuya,Kusumoto, Shuhei,Nozaki, Kyoko
supporting information, p. 12999 - 13004 (2021/08/16)
Oxidative addition reactions of C-H bonds that generate metal-carbon-bond-containing reactive intermediates have played essential roles in the field of organometallic chemistry. Herein, we prepared a cyclopentadienone iridium(I) complex 1 designed for oxidative C-H bond additions. The complex cleaves the various sp2 and sp3 C-H bonds including those in hexane and methane as inferred from their H/D exchange reactions. The hydroxycyclopentadienyl(nitromethyl)iridium(III) complex 2 was formed when the complex was treated with nitromethane, which highlights this elementary metal-ligand cooperative C-H bond oxidative addition reaction. Mechanistic investigations suggested the C-H bond cleavage is mediated by polar functional groups in substrates or another iridium complex. We found that ligands that are more electron-deficient lead to more favorable reactions, in sharp contrast to classical metal-centered oxidative additions. This trend is in good agreement with the proposed mechanism, in which C-H bond cleavage is accompanied by two-electron transfer from the metal center to the cyclopentadienone ligand. The complex was further applied to catalytic transfer-dehydrogenation of tetrahydrofuran (THF).
Catalytic Reduction of Carbon Dioxide Using Cationic Organoaluminum and -Gallium Compounds
Saleh, Mahmoud,Powell, Douglas R.,Wehmschulte, Rudolf J.
, p. 4810 - 4815 (2018/02/07)
Ethide abstraction from Et3M (M = Al and Ga), (2,6-Ph2C6H3)AlEt2, 1, and (2,6-Dipp2C6H3)GaEt2, 2 (Dipp = 2,6-iPr2C6H3), usi
Activation of Chlorinated Methanes at the Surface of Nanoscopic Lewis Acidic Aluminum Fluorides
Siwek, Agnieszka K.,Ahrens, Mike,Feist, Michael,Braun, Thomas,Kemnitz, Erhard
, p. 839 - 845 (2017/03/13)
We report on the activation of chlorinated methanes by the heterogeneous catalysts aluminum chlorofluoride (ACF) and high-surface aluminum fluoride (HS-AlF3) under moderate conditions. For comparison, chlorinated toluenes and 1,2-dichloroethane
Catalytic hydrodefluorination of fluoromethanes at room temperature by silylium-ion-like surface species
Ahrens, Mike,Scholz, Gudrun,Braun, Thomas,Kemnitz, Erhard
supporting information, p. 5328 - 5332 (2013/06/27)
'Al'l about F: Aluminum chlorofluoride (ACF) catalyzes the hydrodefluorination, as well as Friedel-Crafts reactions of fluorinated methanes in the presence of Et3SiH. A surface-bound silylium-ion-like species is considered to be a crucial intermediate in achieving the C-F bond cleavage. Copyright
Catalytic arene H/D exchange with novel rhodium and iridium complexes
Rhinehart, Jennifer L.,Manbeck, Kimberly A.,Buzak, Sara K.,Lippa, Geoffrey M.,Brennessel, William W.,Goldberg, Karen I.,Jones, William D.
experimental part, p. 1943 - 1952 (2012/04/23)
Three novel pendant acetate complexes, [Rh(bdmpza)Cl3] -M+, [Rh(bdmpza)Cl2(py)], and [Ir(bdmpza)Cl3]-M+ (bdmpza = bis(3,5-dimethylpyrazol-1-yl) acetate, M+ = Li+, Na +), were synthesized. Abstraction of halide from these complexes with silver salts yielded species capable of C-H activation of arenes. The catalytic H/D exchange reaction between benzene and trifluoroacetic acid-d was optimized, and these conditions were used to evaluate H/D exchange in other arenes. Branched alkyl substituents in alkyl aromatics showed an affinity toward deuterium exchange in the β-alkyl position only. DFT calculations were performed to determine the mechanism of H/D exchange.
Deoxygenative reduction of carbon dioxide to methane, toluene, and diphenylmethane with [Et2Al]+ as catalyst
Khandelwal, Manish,Wehmschulte, Rudolf J.
supporting information; experimental part, p. 7323 - 7326 (2012/09/08)
The strong Lewis acid [Et2Al]+ catalyzes the reduction of carbon dioxide with hydrosilanes under mild conditions to methane. In benzene solution, the side products toluene and diphenylmethane are also obtained through Lewis acid catalyzed benzene alkylation by reaction intermediates. Copyright
Room Temperature Activation of Aromatic C-H Bonds by Non-Classical Ruthenium Hydride Complexes Containing Carbene Ligands
Giunta, Daniela,H?lscher, Markus,Lehmann, Christian W.,Mynott, Richard,Wirtz, Cornelia,Leitner, Walter
, p. 1139 - 1145 (2007/10/03)
Non-classical ruthenium hydride complexes are promising lead structures for the C-H bond activation and functionalization of aromatic compounds. In the present paper, the preparation and crystallographic characterisation of the first organo-metallic complexes bearing dihydrogen ligands and N-heterocyclic carbene ligands in the same coordination sphere are described. The mixed phosphine/ carbene complex [(IMes)Ru(H)2(H2) 2(PCy3)] (IMes = 1,3-dimesityl-1,3-dihydro-2H-imidazol-2- ylidene; 3a) shows a unique reactivity pattern in the inter- and intramolecular activation of C-H bonds. In particular, complex 3a effects a rapid and remarkably selective intermolecular activation of sp2 C-H bonds in simple aromatic compounds at room temperature.
Arene-mercury complexes stabilized by aluminum and gallium chloride: Catalysts for H/D exchange of aromatic compounds
Borovik, Alexander S.,Barron, Andrew R.
, p. 3743 - 3748 (2007/10/03)
Dissolution of Hg(arene)2(MCI4)2 [arene = C6H5Me, C6H5Et, o-C6H4Me2, C6H3-1,2,3-Me3; M = Al, Ga] in C6D6 results in a rapid H/D exchange and the formation of the appropriate dn-arene and C6D5H. H/D exchange is also observed between C6D6 and the liquid clathrate ionic complexes, [Hg(arene)2(MCl4)]-[MCl4], formed by dissolution of HgCl2 and MCl3 in C6H6, m-C6H4Me2, or p-C6H4Me2. The H/D exchange reaction is found to be catalytic with respect to Hg(arene)2(MCl4)2 and independent of the initial arene ligand. Reaction of a 1:1 ratio Of C6H5Me and C6D6 with 6H5Me)2(MCl4)2 results in an equilibrium mixture of all isotopic isomers: C6H5-xDxMe and C6D6-xHx (x = 0-5). DFT calculations on the model system, Hg(C6H6)2(AlCl4)2 and [Hg(C6H6)2(AlCl4)+, show that the charge on the carbon and proton associated with the shortest Hg···C interactions is significantly higher than that on uncomplexed benzene or HgCl2(C6H6)2. The protonation of benzene by either Hg(C6H6)2(AlCl4)2 or [Hg(C6H6)2(AlCl4)]+ was calculated to be thermodynamically favored in comparison to protonation of benzene by HO2CCF3, a known catalyst for arene H/D exchange. Arene exchange and intramolecular hydrogen transfer reactions are also investigated by DFT calculations.
