Matthias Wagner

Goethe-Universität Frankfurt am Main, Frankfurt, Hesse, Germany

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Publications (215)764.17 Total impact

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    ABSTRACT: The geminal frustrated Lewis pair tBu2 PCH2 B(Fxyl)2 (1; Fxyl=3,5-(CF3 )2 C6 H3 ) is accessible in 65 % yield from tBu2 PCH2 Li and (Fxyl)2 BF. According to NMR spectroscopy and X-ray crystallography, 1 is monomeric both in solution and in the solid state. The intramolecular P⋅⋅⋅B distance of 2.900(5) Å and the full planarity of the borane site exclude any significant P/B interaction. Compound 1 readily activates a broad variety of substrates including H2 , EtMe2 SiH, CO2 /CS2 , Ph2 CO, and H3 CCN. Terminal alkynes react with heterolysis of the C-H bond. Haloboranes give cyclic adducts with strong P-BX3 and weak R3 B-X bonds. Unprecedented transformations leading to zwitterionic XP/BCX3 adducts occur on treatment of 1 with CCl4 or CBr4 in Et2 O. In less polar solvents (C6 H6 , n-pentane), XP/BCX3 adduct formation is accompanied by the generation of significant amounts of XP/BX adducts. FLP 1 catalyzes the hydrogenation of PhCH=NtBu and the hydrosilylation of Ph2 CO with EtMe2 SiH.
    No preview · Article · Feb 2016 · Chemistry - A European Journal
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    ABSTRACT: Reactions of 9-chloro-10,9-oxaboraphenanthrene (1) with the phenyl-, p-tolyl-, m-xylyl-, mesityl-, 2,4,6-tri-iso-propylphenyl-, 3,5-bis(trifluoromethyl)phenyl-, and pentafluorophenyl-Grignard reagents resulted in the formation of the corresponding oxaboraphenanthrene derivatives namely 9-phenyl- (2), 9-p-tolyl- (3), 9-(3,5-dimethylphenyl)- (9-m-xylyl)-, (4), 9-mesityl- (5), 9-(2,4,6-tri-iso-propylphenyl)- (6), 9-(3,5-bis(trifluoromethyl)phenyl)- (7), and 9-(pentafluorophenyl)-10,9-oxaboraphenanthrene (8). 9-Trisyl- (9) and 9-supersilyl-10,9-oxaboraphenanthrene (10) were obtained selectively employing 1 and Li[C(SiMe3)3] or Na[SitBu3] as reactants. The compounds 4-9 were characterized by X-ray crystallography. The fluorescence measurements of 5-9 embedded in PMMA show emission bands with λmax from 344 to 373 nm.
    No preview · Article · Jan 2016
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    ABSTRACT: The solvent-free methyllithium derivatives Li[CH2PR2] (R = tBu, Ph) were prepared via the reaction of CH3PR2 with Li[tBu]. It should be noted that the deprotonation of CH3PtBu2 with Li[tBu] occurred at 60 °C, whereas Li[CH2PPh2] was already formed from CH3PPh2 with Li[tBu] at ambient temperature. The structure determination of di-tert-butylphosphanylmethyllithium was performed by high resolution X-ray powder diffraction analysis at different temperatures. This led to two possible structure solutions with similar quality criteria (space groups Iba2 and I2/a). Therefore CASTEP DFT-D calculations were applied to verify the correct crystal structure. The solid-state structure of di-tert-butylphosphanylmethyllithium consists of alternating edge-sharing six- and four-membered rings, which form a polymeric, infinite double-chain along the crystallographic c axis in the monoclinic space group I2/a. Two Li[CH2PtBu2] units connected via an inversion center form a six-membered Li2C2P2 ring in the chair conformation. The nearly flat four-membered Li2C2 ring, is oriented perpendicularly to the twofold axis.
    No preview · Article · Jan 2016 · Zeitschrift für anorganische und allgemeine Chemie

  • No preview · Article · Dec 2015 · ChemInform
  • Valentin M Hertz · Hans-Wolfram Lerner · Matthias Wagner
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    ABSTRACT: A series of boron-containing polycyclic aromatic hydrocarbons (PAHs) have been synthesized through the Ru-catalyzed cyclization of aryl ene-ynes. The benchtop-stable products show deep blue photoluminescence. Reversible electrochemical reduction is possible at moderate electrode potentials (about -2.0 V vs FcH/FcH(+)); some of the compounds also underwent reversible oxidation. The systematic expansion of the PAH scaffolds permitted the analysis of even subtle structure-property relationships.
    No preview · Article · Oct 2015 · Organic Letters
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    ABSTRACT: Five pairs of perfluorophenyl- and phenyl-substituted tris(pyrazol-1-yl)borate complexes have been prepared and thoroughly investigated, namely, [(C6R′5Bpz3)2Fe], [(C6R′5Bpz3)2Cu], [(C6R′5Bpz3)Mn(CO)3], K[(C6R′5Bpz3)Mo(CO)3], and [(C6R′5Bpz3)Mo(CO)2(2-methallyl)] (R′ = F, H; pz = pyrazol-1-yl). X-ray crystal structure analyses and IR spectroscopical measurements reveal only a minor influence of the spectator substituents on the corresponding parameters. In contrast, significant differences between the redox potentials of the fluorinated and non-fluorinated species are evident in their cyclic voltammograms. Large differences have been found between the crystal packings of the complexes with perfluorinated and non-fluorinated phenyl rings.
    No preview · Article · Sep 2015 · Berichte der deutschen chemischen Gesellschaft
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    ABSTRACT: The free cyclohexasilane Si6Cl12 (1) was obtained in 66% yield from the corresponding Cl(-) diadduct [nBu4N]2[1·2Cl] and AlCl3 in C6H6. The substituted cyclohexasilane 1,1-(Cl3Si)2Si6Cl10 (2), however, cannot be liberated from [nBu4N]2[2·2Cl] under comparable reaction conditions. Instead, a mixture of several products was obtained, from which the oligosilane Si19Cl36 (3) crystallized in low yields. X-ray crystallography revealed 3 to consist of two Si5 rings, bridged by one silicon atom. Compound 1 possesses Lewis acidic sites above and below the ring centroid. Competition experiments reveal that their corresponding acid strengths are comparable to that of BCl3. The reaction of 1 with 6 equiv of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (Idipp) leads to a complete breakdown of the cyclic scaffold and furnishes the dichlorosilylene adduct Idipp-SiCl2.
    No preview · Article · Sep 2015 · Inorganic Chemistry
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    ABSTRACT: The high-yield synthesis of a boron-doped [4]helicene was achieved through a Ni-mediated Yamamoto C-C-coupling reaction; the moderate distortion of the molecular scaffold confers excellent solubility to the air- and water-stable green luminophore.
    No preview · Article · Sep 2015 · Chemical Communications
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    ABSTRACT: Herein we show that replacing the two meso carbon atoms of the polycyclic aromatic hydrocarbon (PAH) bisanthene by boron atoms transforms a near-infrared dye into an efficient blue luminophore. This observation impressively illustrates the impact of boron doping on the frontier orbitals of PAHs. To take full advantage of this tool for the targeted design of organic electronic materials, the underlying structure-property relationships need to be further elucidated. We therefore developed a modular synthesis sequence based on a Peterson olefination, a stilbene-type photocyclization, and an Si-B exchange reaction to substantially broaden the palette of accessible polycyclic aromatic organoboranes and to permit a direct comparison with their PAH congeners. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    No preview · Article · Jun 2015 · Angewandte Chemie
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    ABSTRACT: The ion-like silylium compounds tBu3Si–F–Al[OC(CF3)3]3 and Me3Si–F–Al[OC(CF3)3]3 were prepared by degradation of the halonium salts [R3Si–X–SiR3][Al{OC(CF3)3}4] {1a(X): R = tBu, X = Br, I; 1b(X): R = Me, X = Br, I}. The bromonium and iodonium salts 1a(Br), 1a(I), 1b(Br), and 1b(I) were quantitatively obtained from R3SiX (R = Me, tBu) and [Ag][Al{OC(CF3)3}4] in dichloromethane at –50 °C. However, the related fluoronium and chloronium salts, [R3Si–X–SiR3][Al{OC(CF3)3}4] {1a(X): R = tBu, X = F, Cl; 1b(X): R = Me, X = F, Cl}, could not be generated under these conditions. Generally, at low temperatures (< –50 °C) the halonium salts 1a(Br), 1a(I), 1b(Br), and 1b(I) are stable compounds. However, at higher temperatures 1a(Br), 1a(I), 1b(Br), and 1b(I) undergo R3SiX (R = Me, tBu; X = Br, I) elimination to form the highly reactive silyl cations [R3Si]+ (R = Me, tBu). Two different decomposition pathways were observed in the thermolysis of halonium compounds 1a(Br), 1a(I), 1b(Br), and 1b(I): (1) the silylium cations [R3Si]+ reacted with dichloromethane, forming 1a(Cl) as well as 1b(Cl); (2) the silylium cations [R3Si]+ degraded the counteranion to give tBu3Si–F–Al[OC(CF3)3]3 and Me3Si–F–Al[OC(CF3)3]3 along with epoxide C4F8O. Both ion-like silylium compounds could be isolated, and single crystals of tBu3Si–F–Al[OC(CF3)3]3 (orthorhombic, Pnma) as well as Me3Si–F–Al[OC(CF3)3]3 (orthorhombic, P212121) were grown from dichloromethane at room temp. Supersilylium [tBu3Si]+ has higher Lewis acidity than [Me3Si]+, as demonstrated by the reaction of 1a(I) with Me3SiF. Thereby the fluoronium ion 1b(F), along with tBu3SiF and tBu3SiI, was formed.
    No preview · Article · Apr 2015 · Berichte der deutschen chemischen Gesellschaft
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    ABSTRACT: Four new BMes2-functionalized indolizine derivatives (Mes = mesityl) have been prepared via the cycloaddition reaction between pyrido[2,1-a]isoindole (A) or pyrrolo[1,2-a]pyridine (B) and BMes2-containing alkynes. All four compounds are brightly blue or blue-green fluorescent with λem = 428-495 nm and Φ = 0.27-0.68, depending on the substitution position of the BMes2 group. Experimental and TD-DFT computational data indicated that the primary electronic transitions responsible for the fluorescence of 1-4 are from HOMO to LUMO (π → π*) rather than charge transfer from N → B, which is in agreement with previous findings suggesting that the lone-pair on N is delocalized throughout the N-heterocycles.
    Full-text · Article · Apr 2015 · Organic Letters
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    ABSTRACT: 9,10-(Bpin)2 -anthracene (3, HBpin=pinacolborane) was synthesized from 9,10-dibromoanthracene in a stepwise lithiation/borylation sequence. The reaction of 3 with highly activated magnesium furnished the diborylated magnesium anthracene 4, which was quenched in situ with ethereal HCl to yield cis-9,10-(Bpin)2 -DHA (cis-5, DHA=9,10-dihydroanthracene). Compound cis-5, in turn, can be reduced with Li[AlH4 ] in THF to give its diborate Li2 [cis-9,10-(BH3 )2 -DHA] (Li2 [cis-6]). In the crystal lattice, the THF solvate Li2 [cis-6]⋅3 THF establishes a dimeric structure with Li-(μ-H)-B coordination modes. Hydride abstraction from Li2 [cis-6] with Me3 SiCl yields the BHB-bridged DHA Li[7]. This product can also be viewed as a unique cyclic B2 H7 (-) derivative with a hydrocarbon backbone. Treatment of Li2 [cis-6] with the stronger hydride abstracting agent Me3 SiOTf (HOTf=trifluoromethanesulfonic acid) in THF affords the THF diadduct of cis-9,10-(BH(OTf))2 -DHA. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    No preview · Article · Apr 2015 · Chemistry - A European Journal
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    ABSTRACT: Silicon analogues of the most prominent carbon nanostructures, namely, hollow spheroidals such as C60 and the fullerene family, have been unknown to date. Herein we show that discrete Si20 dodecahedra, stabilized by an endohedral guest and valence saturation, are accessible in preparative yields through a chloride-induced disproportionation reaction of hexachlorodisilane in the presence of tri(n-butyl)amine. X-ray crystallography revealed that each silicon dodecahedron contains an endohedral chloride ion that imparts a net negative charge. Eight chloro substituents and twelve trichlorosilyl groups are attached to the surface of each cluster in a strictly regioregular arrangement, a thermodynamically preferred substitution pattern according to quantum-chemical assessment. Our results demonstrate that the wet-chemical self-assembly of a complex, monodisperse Si nanostructure is possible under mild conditions starting from simple Si2 building blocks. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    No preview · Article · Mar 2015 · Angewandte Chemie International Edition in English
  • [Show abstract] [Hide abstract]
    ABSTRACT: Silicon analogues of the most prominent carbon nanostructures, namely, hollow spheroidals such as C60 and the fullerene family, have been unknown to date. Herein we show that discrete Si20 dodecahedra, stabilized by an endohedral guest and valence saturation, are accessible in preparative yields through a chloride-induced disproportionation reaction of hexachlorodisilane in the presence of tri(n-butyl)amine. X-ray crystallography revealed that each silicon dodecahedron contains an endohedral chloride ion that imparts a net negative charge. Eight chloro substituents and twelve trichlorosilyl groups are attached to the surface of each cluster in a strictly regioregular arrangement, a thermodynamically preferred substitution pattern according to quantum-chemical assessment. Our results demonstrate that the wet-chemical self-assembly of a complex, monodisperse Si nanostructure is possible under mild conditions starting from simple Si2 building blocks.
    No preview · Article · Mar 2015 · Angewandte Chemie
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    ABSTRACT: Reduction of the bis(9-borafluorenyl)methane 1 with excess lithium furnishes the red dianion salt Li2[1]. The corresponding dark green monoanion radical Li[1] is accessible through the comproportionation reaction between 1 and Li2[1]. EPR spectroscopy on Li[1] reveals hyperfine coupling of the unpaired electron to two magnetically equivalent boron nuclei (a((11)B) = 5.1±0.1 G, a((10)B) = 1.7±0.2 G). Further coupling is observed to the unique B-CH-B bridgehead proton (a((1)H) = 7.2±0.2 G) and to eight aromatic protons (a((1)H) = 1.4±0.1 G). According to X-ray crystallography, the B∙∙∙B distances continuously decrease along the sequence 1 → [1](•-) → [1](2-) with values of 2.534(2) Å, 2.166(4) Å, and 1.906(3) Å, respectively. Protonation of Li2[1] leads to the cyclic borohydride species Li[1H] featuring a B-H-B two-electron-three-center bond. This result strongly indicates a nucleophilic character of the boron atoms; the reaction can also be viewed as rare example of the protonation of an element-element σ bond. According to NMR spectroscopy, EPR spectroscopy, and quantum-chemical calculations, [1](2-) represents a closed-shell singlet without any spin contamination. Detailed wavefunction analyses of [1](•-) and [1](2-) reveal strongly localized interactions of the two boron pz-type orbitals, with small delocalized contributions of the 9-borafluorenyl π systems. Overall, our results provide evidence for a direct B-B one-electron and two-electron bonding interaction in [1](•-) and [1](2-), respectively.
    No preview · Article · Feb 2015 · Journal of the American Chemical Society
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    ABSTRACT: Double lithiation of 9,10-dihydroanthracene (DHA) or 6,13-dihydropentacene (DHP) with nBuLi, followed by the addition of B2(NMe2)2Cl2, affords 9,10-DHA-9,10-diyl- (1a) or 6,13-DHP-6,13-diyl-bridged B2(NMe2)2 (1p) in good yields. Upon treatment with Pt(PEt3)3 in C6H6 at 60 °C, both compounds cleanly insert a Pt(PEt3)2 moiety into their B–B bonds to furnish the corresponding diboryl Pt(II) complexes 2a and 2p. Compound 2a reacts with excess tBuCCH to give an equimolar mixture of the B–(tBu)C═C(H)–B-bridged 9,10-DHA 3 and Pt(η2-tBuCCH)(PEt3)2 (4). The addition of isocyanides to either the Pt(II) complex 2a or the Pt-free species 1a yields bicyclic products, in which a 9,10-DHA-9,10-diyl fragment is spanned by a B–C(═NR)–B linker (R = tBu (5), iPr (6)). Both 5 and 6 are extremely prone to hydrolysis. In the case of 6, a water-induced rearrangement reaction leading to a B–C-bridged 9,10-DHA 8 was observed.
    No preview · Article · Dec 2014 · Organometallics
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    ABSTRACT: The reaction of biphenylene (1) with Et2 SiH2 in the presence of [Ni(PPhMe2 )4 ] results in the formation of a mixture of 2-diethylhydrosilylbiphenyl [2(Et2 HSi)] and 9,9,-diethyl-9-silafluorene (3). Silafluorene 3 was isolated in 37.5 % and 2(Et2 HSi) in 36.9 % yield. The underlying reaction mechanism was elucidated by DFT calculations. 4-Methyl-9,9-diethyl-9-silafluorene (7) was obtained selectively from the [Ni(PPhMe2 )4 ]-catalyzed reaction of Et2 SiH2 and 1-methylbiphenylene. By contrast, no selectivity could be found in the Ni-catalyzed reaction between Et2 SiH2 and the biphenylene derivative that bears tBu substituents in the 2- and 7-positions. Therefore, two pairs of isomers of tBu-substituted silafluorenes and of the related diethylhydrosilylbiphenyls were formed in this reaction. However, a subsequent dehydrogenation of the diethylhydrosilylbiphenyls with Wilkinson's catalyst yielded a mixture of 2,7-di-tert-butyl-9,9-diethyl-9-silafluorene (8) and 3,6-di-tert-butyl-9,9-diethyl-9-silafluorene (9). Silafluorenes 8 and 9 were separated by column chromatography.
    No preview · Article · Nov 2014 · Chemistry - An Asian Journal
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    ABSTRACT: Common wisdom has it that organoboranes are readily oxidized. Described herein is that also their reduction can result in remarkable chemistry. Treatment of dimeric 9H-9-borafluorene with Li metal in toluene yields two strikingly different classes of compounds. One part of the sample reacts in a way similar to B2H6, thus affording an aryl(hydro)borane cluster reminiscent of the [B3H8]− anion. The other part furnishes a dianionic boron-doped graphene flake devoid of hydrogen substituents at the boron centers and featuring a central BB bond. A change in the solvent to THF allows an isolation of this dibenzo[g,p]chrysene analogue in good yields.
    No preview · Article · Sep 2014 · Angewandte Chemie International Edition
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    ABSTRACT: A surprisingly simple preparative procedure, addition of Si2Cl6 to a solution of [nBu4N]Cl in CH2Cl2, leads to the formation of the chloride-complexed cyclic dianions [Si6Cl12⋅2Cl]2−, [(SiCl3)Si6Cl11⋅2Cl]2−, or [1,y-(SiCl3)2Si6Cl10⋅2Cl]2− (y=1, 3, 4), depending on the stoichiometric ratio of the reactants and the reaction temperature (25–85 °C). Below −40 °C the open-chain oligosilane chloride adducts [Si3Cl9]−, [Si3Cl10]2−, [Si4Cl11]−, and [Si6Cl15]− are formed, again depending on the reaction conditions chosen. All species were characterized by X-ray crystallography. The underlying reaction mechanism is elucidated by DFT calculations. It incorporates all experimental findings and involves a few key elementary steps: 1) chloride-induced liberation of SiCl3− or higher silanides, 2) their addition to neutral silanes yielding larger oligosilane chloride adducts, 3) dimerization of larger silanides to (substituted) cyclohexasilane dichloride adducts with inverse sandwich structure.
    No preview · Article · Jul 2014 · Chemistry - A European Journal
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    ABSTRACT: In the oxidative process of the supersilanide anion [SitBu3]−, radical species are generated. The continuous wave (cw)-EPR spectrum of the reaction solution of Na[SitBu3] with O2 revealed a signal, which could be characterized as disupersilylperoxo radical anion [tBu3SiOOSitBu3]⋅− affected by sodium ions though ion-pair formation. A mechanism is suggested for the oxidative process of supersilanide, which in a further step can be helpful in a better understanding of the oxidation process of isoelectronic phosphanes.
    No preview · Article · Jul 2014 · Chemistry - A European Journal

Publication Stats

3k Citations
764.17 Total Impact Points

Institutions

  • 1999-2015
    • Goethe-Universität Frankfurt am Main
      • Institut für Anorganische und Analytische Chemie
      Frankfurt, Hesse, Germany
  • 2008
    • University Hospital Frankfurt
      Frankfurt, Hesse, Germany
  • 1997-2007
    • Technische Universität München
      München, Bavaria, Germany
  • 1995
    • Deutsches Herzzentrum München
      München, Bavaria, Germany