Matthias Wagner

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

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Publications (206)682.32 Total impact

  • [Show abstract] [Hide abstract]
    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.
    Angewandte Chemie 06/2015; DOI:10.1002/ange.201502977
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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.
    Berichte der deutschen chemischen Gesellschaft 04/2015; DOI:10.1002/ejic.201500323
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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.
    Organic Letters 04/2015; 17(10). DOI:10.1021/acs.orglett.5b00994 · 6.32 Impact Factor
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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.
    Chemistry - A European Journal 04/2015; 21(22). DOI:10.1002/chem.201500541 · 5.70 Impact Factor
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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.
    Angewandte Chemie International Edition in English 03/2015; 54(18). DOI:10.1002/anie.201412050 · 13.45 Impact Factor
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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.
    Angewandte Chemie 03/2015; 127(18). DOI:10.1002/ange.201412050
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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.
    Journal of the American Chemical Society 02/2015; 137(10). DOI:10.1021/jacs.5b01192 · 11.44 Impact Factor
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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.
    Organometallics 12/2014; 33(23):6967-6974. DOI:10.1021/om501087u · 4.25 Impact Factor
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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.
    Chemistry - An Asian Journal 11/2014; 9(11). DOI:10.1002/asia.201402599 · 3.94 Impact Factor
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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.
    Angewandte Chemie International Edition 09/2014; 53(39). DOI:10.1002/anie.201405957 · 11.34 Impact Factor
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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.
    Chemistry - A European Journal 07/2014; 20(30). DOI:10.1002/chem.201402655 · 5.70 Impact Factor
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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.
    Chemistry - A European Journal 07/2014; 20(33). DOI:10.1002/chem.201403854 · 5.70 Impact Factor
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    ABSTRACT: The reaction of (3,5-(CF3)2C6H3)Li ((Fxyl)Li) with BH3·SMe2 in Et2O furnishes Li[(Fxyl)BH3] in an essentially quantitative yield. Hydride abstraction with Me3SiCl followed by the addition of a second equivalent of (Fxyl)Li gives Li[(Fxyl)2BH2] in 71% yield. Treatment of Li[(Fxyl)2BH2] with 1 equiv of Me3SiCl and a subsequent targeted methanolysis provide access to the methoxyborane (Fxyl)2BOMe. The latter compound serves as starting material for the synthesis of the haloboranes (Fxyl)2BX (X = F, Cl, Br) through the reaction with KHF2/Me3SiCl, BCl3, and BBr3, respectively. All three haloboranes, as well as key synthesis intermediates, have been structurally characterized by X-ray crystallography.
    Organometallics 06/2014; 33(13):140626134355006. DOI:10.1021/om500476d · 4.25 Impact Factor
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    ABSTRACT: The reaction of 1,2-C6H4(P(O)-t-Bu2)(Li) (Ph*Li) with B(OMe)3 furnishes a mixture of Li[Ph*B(OMe)3] (Li[2a]) and Ph*B(OMe)2 (2b). Further treatment with Li[AlH4] provides the trihydroborate Li[Ph*BH3] (Li[3]), which can subsequently be converted into the intramolecular P═O–B adduct Ph*BH2 (4) through hydride abstraction with Me3SiCl. Addition of C6F5MgBr yields Mg[Ph*BH2(C6F5)]2 (Mg[5]2), which is inert toward Me3SiCl but reacts with water to give Ph*B(H)C6F5 (6). Upon addition of further C6F5MgBr, a mixture is formed, from which crystals of Mg[Ph*BH(C6F5)2]2 (Mg[7]2) were obtained. The reaction of Ph*Li with (C6F5)2BH·SMe2 provides access to Li[7], but again with limited product selectivity. The targeted acidic hydrolysis of Li[7] furnishes Ph*B(C6F5)2 (8), while Mg[7]2 reacts back to 6. The anions of the hydroborates Li[3] and Mg[5]2 act as BH2,O-chelating ligands toward their metal ions. Therefore, Li[Ph*2BH2] (Li[13]) was also synthesized to obtain the corresponding pincer-type species. 4, 6, and 8 exist as water-stable intramolecular P═O–B adducts both in solution and in the solid state. X-ray crystallography and 31P NMR spectroscopy indicate an increase in the Lewis acidity of the boryl groups in the order 4 < 6 < 8.
    Organometallics 06/2014; 33(12):3163–3172. DOI:10.1021/om500385h · 4.25 Impact Factor
  • Christian Reus, Matthias Wagner
    Nature Chemistry 06/2014; 6(6):466-7. DOI:10.1038/nchem.1953 · 23.30 Impact Factor
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    ABSTRACT: Air- and water-stable, π-conjugated [−donor–acceptor−]n oligomers containing thiophene fragments as donors and 9,10-dimesityl-9,10-dihydro-9,10-diboraanthracene (DBA(Mes)2) as acceptor units were prepared through Stille-type C–C-coupling protocols. The reaction between 2,6-dibromo-DBA(Mes)2 (1), 2,7-dibromo-DBA(Mes)2 (2), 2-bromo-6,7-dimethyl-DBA(Mes)2 (3), and 2,5-bis(trimethylstannyl)thiophene (7) furnished monodisperse, short-chain model systems 80 (2 × DBA(Mes)2, 1 × 2,5-thienylene) and 81 (3 × DBA(Mes)2, 2 × 2,5-thienylene) after GPC separation. In the absence of 3, the oligomerization of 1/2 with 7 provided analogous longer chain macromolecules 9 (MALDI–MS reveals up to 7 repeating units; GPC indicates also significantly longer chains). UV/vis absorption spectroscopy suggests that the obtained chain lengths of 9 are already sufficient to reach the maximum effective conjugation length (the lower limit of the HOMO–LUMO band gap corresponds to 2.3 eV). 9 gives rise to a dark orange fluorescence, both in C6H6 solution (f = 47%) and as thin film (f = 13%).
    Macromolecules 05/2014; 47(11):3727–3735. DOI:10.1021/ma500518x · 5.93 Impact Factor
  • ChemInform 05/2014; 45(20). DOI:10.1002/chin.201420109
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    ABSTRACT: Is one electron sufficient to bring about significant σ bonding between two atoms? The chemist's view on the chemical bond is usually tied to the concept of shared electron pairs, and not too much experimental evidence exists to challenge this firm belief. Whilst species with the unusual one-electron σ-bonding motif between homonuclear atoms have so far been identified mainly by spectroscopic evidence, we present herein the first crystallographic characterization, augmented by a detailed quantum-chemical validation, for a radical anion featuring a B⋅B one-electron-two-center σ bond.
    Angewandte Chemie International Edition 05/2014; 53(19). DOI:10.1002/anie.201402158 · 11.34 Impact Factor
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    ABSTRACT: The reaction of 4-chloro-1,2-dimethyl-4-supersilylsila-1-cyclopentene (2 a) with Li[NiPr2 ] at -78 °C results in the formation of the formal 1,4-addition product of the silacyclopentadiene derivative 3,4-dimethyl-1-supersilylsila-1,3-cyclopentadiene (4 a) with 2,3-dimethyl-4-supersilylsila-1,3-cyclopentadiene (5 a). In addition the respective adducts of the Diels-Alder reactions of 4 a+4 a and 4 a+5 a were obtained. Compound 4 a, which displays an s-cis-silacyclopentadiene configuration, reacts with cyclohexene to form the racemate of the [4+2] cycloadduct of 4 a and cyclohexene (9). In the reaction between 4 a and 2,3-dimethylbutadiene, however, 4 a acted as silene as well as silacyclopentadiene to yield the [2+4] and [4+2] cycloadducts 10 and 11, respectively. The constitutions of 9, 10, and 11 were confirmed by NMR spectroscopy and their crystal structures were determined. Reaction of 4-chloro-1,2-dimethyl-4-tert-butyl-4-silacyclopent-1-ene (2 c) with KC8 yielded the corresponding disilane (12), which was characterized by X-ray crystal structure analysis (triclinic, P$\bar 1$). DFT calculations are used to unveil the mechanistic scenario underlying the observed reactivity.
    Chemistry - A European Journal 04/2014; 20(16). DOI:10.1002/chem.201302544 · 5.70 Impact Factor
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    ABSTRACT: The reaction between the bisborate Li2[o-C6H4(BH3)2] and 2 equivalents of an appropriate pyrazole derivative (Hpz(R)) in the presence of Me3SiCl yields o-phenylene-bridged pyrazaboles HB(μ-pz(R))2(μ-o-C6H4)BH (; Hpz(R) = 4-iodopyrazole (), 4-(trimethylsilyl)pyrazole (), 3,5-dimethylpyrazole (), 3,5-di(tert-butyl)pyrazole (), 3,5-bis(trifluoromethyl)pyrazole ()). The synthesis approach thus provides access to uncharged B-N triptycenes bearing (i) functionalisable groups, (ii) electron-donating or -withdrawing substituents and (iii) pyrazole rings of varying steric demand. Treatment of p-R*C6H4BBr2 with the potassium tris(pyrazol-1-yl)borates K[HBpz3] or K[p-R*C6H4Bpz3] yields cationic pyrazolyl-bridged pyrazaboles [p-BrC6H4B(μ-pz)3BH]Br ([]Br) and [p-R*C6H4B(μ-pz)3Bp-C6H4R*]Br (R* = Br ([]Br), I ([]Br), SiMe3 ([]Br)), which can be regarded as full B-N analogues of triptycene. The B-H bonds of and []Br are unreactive towards tBuC[triple bond, length as m-dash]CH even at temperatures of 80 °C, thereby indicating an appreciable thermal stability of the corresponding B-N cage bonds. Most of the cage compounds are sufficiently inert towards water to allow quick aqueous workup. However, NMR spectroscopy in CD3OD solution reveals degradation of or []Br to the corresponding pyrazoles and o-C6H4(B(OCD3)2)2 or p-BrC6H4B(OCD3)2/B(OCD3)3. The diphenylated species []Br is significantly more stable under the same measurement conditions; even after 76 d, most of the material degrades only to the stage of the syn/anti-pyrazaboles p-BrC6H4(CD3O)B(μ-pz)2B(OCD3)p-C6H4Br (/). A derivatisation of []Br with nBu3SnC[triple bond, length as m-dash]CtBu through Stille-type coupling reactions furnishes the alkynyl derivative [p-tBuC[triple bond, length as m-dash]CC6H4B(μ-pz)3Bp-C6H4C[triple bond, length as m-dash]CtBu]Br ([]Br). Larger B-N aggregates are also accessible: treatment of the tetrakisborate Li4[1,2,4,5-C6H2(BH3)4] with 4 equivalents of Hpz(R) in the presence of Me3SiCl leads to the corresponding B-N pentiptycenes (Hpz(R) = 3,5-bis(trifluoromethyl)pyrazole (), 4-(trimethylsilyl)pyrazole (), 3,5-dimethylpyrazole (), 3,5-di(tert-butyl)pyrazole ()).
    Dalton Transactions 03/2014; 43(22). DOI:10.1039/c4dt00442f · 4.10 Impact Factor

Publication Stats

2k Citations
682.32 Total Impact Points

Institutions

  • 2000–2015
    • Goethe-Universität Frankfurt am Main
      • Institut für Anorganische und Analytische Chemie
      Frankfurt, Hesse, Germany
  • 2003–2009
    • University Hospital Frankfurt
      Frankfurt, Hesse, Germany
  • 1996–2006
    • Università degli Studi di Siena
      Siena, Tuscany, Italy
  • 1995–2006
    • Technische Universität München
      München, Bavaria, Germany
  • 2005
    • Universidad del País Vasco / Euskal Herriko Unibertsitatea
      Leioa, Basque Country, Spain
  • 2001
    • Max Planck Institute for Solid State Research
      Stuttgart, Baden-Württemberg, Germany
  • 1995–1998
    • Deutsches Herzzentrum München
      München, Bavaria, Germany