Arenium acid catalyzed deuteration of aromatic hydrocarbons

The arenium acid [mesitylene–H]+ has been shown to be an extraordinarily active H/D exchange catalyst for the perdeuteration of polycyclic aromatic hydrocarbons. The reactions take place under ambient conditions in C6D6 as an inexpensive deuterium source. High isolated yields and excellent degrees of deuterium incorporation were achieved using the substrates p-terphenyl, fluoranthene, pyrene, triphenylene, and corannulene

Competition between π-arene and lone-pair halogen coordination of silylium ions?

In 2,6-diarylphenylSiR(2) cations, the 2,6-diarylphenyl (m-terphenyl) scaffold blocks incoming nucleophiles and stabilizes the positive charge at silicon by lateral ring interactions. Direct ortho-halogen and π-electron-rich face coordination to silicon has been seen. For a series of cations bearing 2,6-difluoro-2',6'-dimethyl-X(n)-substituted rings, the relative contribution of these two modes of stabilization has been assessed. Direct coordination from an aryl fluoride is found to be comparable to that from the mesityl π-face

Proton-catalyzed, silane-fueled Friedel-Crafts coupling of fluoroarenes

The venerable Friedel-Crafts reaction appends alkyl or acyl groups to aromatic rings through alkyl or acyl cation equivalents typically generated by Lewis acids. We show that phenyl cation equivalents, generated from otherwise unreactive aryl fluorides, allow extension of the Friedel-Crafts reaction to intramolecular aryl couplings. The enabling feature of this reaction is the exchange of carbon-fluorine for silicon-fluorine bond enthalpies; the reaction is activated by an intermediate silyl cation. Catalytic quantities of protons or silyl cations paired with weakly coordinating carborane counterions initiate the reactions, after which proton transfer in the final aromatization step regenerates the active silyl cation species by protodesilylation of a quaternary silane. The methodology allows the high-yield formation of a range of tailored polycyclic aromatic hydrocarbons and graphene fragments

Highly selective gas separation by two isostructural boron cluster pillared MOFs

Two isostructural closo-dodecaborate [B12H12]2- pillared metal organic frameworks (MOFs), BSF-4 and BSF-9, were synthesized and compared in the performance of selective gas adsorption and separation. BSF-9 with symmetrical interpenetration and two contracted 1D channel exhibited efficient uptake of C2H2 (85.1/76.3 mLg−1, 278/298 K) with high separation selectivity over C2H4 (41.4, 298 K), outperforming BSF-4 (7.3, 298 K) and many benchmark MOFs. The selectivity of C2H6/CH4, CO2/CH4, CO2/N2 on BSF-9 (25.2, 9.9, 56.6) and BSF-4 (19.0, 8.9, 41.7) was all relatively high and comparable. The practical gas separation ability for C2H2/C2H4 mixtures on BSF-9 was confirmed by mixed gas breakthrough experiments with negligible capacity loss after 4 cycles, indicating its potential for purification of ethylene from acetylene-containing industrial gas mixtures. The C2H2 and C2H4 bonding sites and bonding energies within the framework of BSF-9 were further compared by density functional theory (DFT) study, indicating that C2H2 can be trapped tightly between two anionic [B12H12]2- by four synergistic dihydrogen bonds while C2H4 only interacts with single [B12H12]2- with weaker bonding energy. BSF-4 with asymmetrical interpenetration and single extended 1D channel showed higher selectivity of C3H8/CH4 (138.5, 298 K) than that of BSF-9 (64.0, 298 K). Inverse ambient adsorption capacity of C3H8 < C2H6 was observed in BSF-9 due to the small pore window and 1D channel

Through-space interactions in enshroudedm-terphenylsilanes

A series of m-terphenyl-substituted silanes was prepared and studied with regard to the steric and electronic interactions between the silyl core and the terphenyl shroud. Only weak conformational preferences were observed for the core, but the π-basicity of the lateral rings led to distinct nuclear magnetic resonance shifts, and o-fluorine atoms led to through-space coupling effects

Synthesis and crystal structure of a silyl-stabilized allyl cation formed by disruption of an arene by a protonation-hydrosilylation sequence

Sly silyl caught in the act: Protonation of a mesitylene ring by the strongly acidic arenium carborane [CH(3)C(6)H(6)]- [CHB(11)Me(5)Br(6)] initiates a cascade reaction that results in a stable beta-silyl allyl cation (see picture, H yellow, C blue, silyl allyl group red). Remarkably, the driving force in the reaction suffices to disrupt a stable aromatic ring in favor of a cationic reactive intermediate

Cu(i) and Ag(i) complexes of 7,10-bis-N-heterocycle-diazafluoranthenes: programmed molecular grids?

Reactions of 7,10-disubstituted diazafluoranthene derivatives with three different silver(I) salts AgX (X = [PF6]−, [SbF6]−, [CB11HCl11]−) and [Cu(CH3CN)4]PF6 afforded complexes exhibiting five different motifs. The crystal structures of the free ligands and nine new complexes from this series of reactions are reported. The use of 2,5-di-tert-butyl-7,10-di(pyridin-2-yl)-8,9-diazafluoranthene as a ligand leads to the formation of the tetranuclear compounds [Ag4(C32H30N4)4][PF6]4•3C6H6•4MeCN, [Ag4(C32H30N4)4]- [SbF6]4•4C5H12 and [Cu4(C32H30N4)4][PF6]4•8C3H6O, which exhibit “propeller” and saddle-type geometry, respectively, as well as a dinuclear complex [Ag2(C32H30N4)2][CHB11Cl11]2•4C6H4Cl2•CH2Cl2. The reactions involving the less sterically hindered 2,5-di-tert-butyl-7,10-di-(pyrimidin-2-yl)-8,9-diazafluoranthene and 2,5-di-tert-butyl-7,10-di(thiazol-2-yl)-8,9-diazafluoranthene afforded crystals of the dinuclear complexes [Ag2(C30H28N6)2][PF6]2•0.5CH2Cl2•0.5C6H5Cl•0.5C6H12, [Ag2(C30H28N6)2][SbF6]2•C3H6O•0.5C6H14•0.5C6H6, the polymeric species [Ag2(C28H26N4S2)2]n•2n[PF6]n•nC3H6O and the tetranuclear compounds [Cu4(C26H25N4S2)4][PF6]4•2CHCl3•2C3H6O and [Cu4(C30H28N6)4][PF6]4•2.17H2O, which possess saddle and grid-like architectures, respectively. Conformational analysis of the free ligands showed that they exhibit N–C–C–N torsion angles ranging from syn clinal (58°) to fully anti-periplanar conformations; the syn clinal conformation dominates in the complexes. The relative energies of the possible structural conformations of the synthesized ligands, as well as of oxazole disubstituted diazafluoranthenes, were calculated using density functional theory at the B97D/Def2-TZVPP level of theory

Arenium Acid Catalyzed Deuteration of Aromatic Hydrocarbons

The arenium acid [mesitylene–H]⁺ has been shown to be an extraordinarily active H/D exchange catalyst for the perdeuteration of polycyclic aromatic hydrocarbons. The reactions take place under ambient conditions in C₆D₆ as an inexpensive deuterium source. High isolated yields and excellent degrees of deuterium incorporation were achieved using the substrates <i>p</i>-terphenyl, fluoranthene, pyrene, triphenylene, and corannulene

Synthesis and crystal structure of a silyl-stabilized allyl cation formed by disruption of an arene by a protonation-hydrosilylation sequence.

Sly silyl caught in the act: Protonation of a mesitylene ring by the strongly acidic arenium carborane [CH(3)C(6)H(6)]- [CHB(11)Me(5)Br(6)] initiates a cascade reaction that results in a stable beta-silyl allyl cation (see picture, H yellow, C blue, silyl allyl group red). Remarkably, the driving force in the reaction suffices to disrupt a stable aromatic ring in favor of a cationic reactive intermediate