95 research outputs found

    Hydrogen-Bonded Chains and Networks of Triptycene-Based Triboronic Acid and Tripyridinone

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    The synthesis of 2,7,14-triptycene triboronic acid <b>1</b> and triptycene tripyridinone <b>2</b>, as well as their packings in the crystalline states, was studied. Both compounds show pronounced aggregation by hydrogen bonding, thus forming supramolecular polymeric chains or interpenetrated networks depending on the solvent mixtures used for crystallization. In all examples, two of the three hydrogen bonding motifs in each molecule formed cyclic dimers, leaving the third site either masked by solvents or for the formation of another hydrogen bond with the dimeric units. The influence of the solvent is discussed

    Rigid π‑Extended Triptycenes via a Hexaketone Precursor

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    A high-yielding synthesis of a rigid hexaketone is presented that can be transformed into π-extended <i>D</i><sub>3<i>h</i></sub>-symmetric triptycene derivatives with high internal molecular free volumes (IMFVs). The products show excellent photophysical properties combined with high specific surface areas

    Synthesis of Triphenylene-Based Triptycenes via Suzuki–Miyaura Cross-Coupling and Subsequent Scholl Reaction

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    A two-step method (Suzuki–Miyaura cross-coupling, followed by Scholl oxidation) to triphenylene-based triptycenes is described, rendering a variety of π-extended triptycenes accessible in high yields and without the necessity of column chromatography purification. The versatility of this reaction has been demonstrated in the synthesis of a supertriptycene in only four steps and high yields

    1,2-Bis(di-<i>tert</i>-butylphosphino)imidazole (<b>dtbpi</b>): A Versatile Imidazole-Based, Rigid, Bulky Bisphosphine Ligand for Transition Metals

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    A bulky bisphosphine, 1,2-bis­(di-<i>tert</i>-butylphosphino)­imidazole (<b>dtbpi</b>), featuring a rigid imidazole backbone, was synthesized in a simple two-step procedure. The ligand’s coordination chemistry and electron-donating abilities were investigated in the complexes (<b>dtbpi</b>)­Ni­(FDN) (<b>3</b>) and [(<b>dtbpi</b>)­Rh­(CO)<sub>2</sub>]­BF<sub>4</sub> (<b>4</b>). Protonation of <b>4</b> at the ligand backbone’s nitrogen with strong Brþnsted acids such as HBF<sub>4</sub> and HBAr<sub>F</sub> gave the dicationic dicarbonyl complexes [(<b>H-dtbpi</b><sup><b>+</b></sup>)­Rh­(CO)<sub>2</sub>]­(BF<sub>4</sub>)­(BAr<sub>F</sub>) (<b>5a</b>) and [(<b>H-dtbpi</b><sup><b>+</b></sup>)­Rh­(CO)<sub>2</sub>]­(BF<sub>4</sub>)<sub>2</sub> (<b>5b</b>), which served as model complexes of the ligand’s imidazolium-phosphine form and permitted characterization of its donating character. In order to evaluate solely the different electronic characters of the two isosteric P donors, the complexes (<b>dtbpi</b>)­PdCl­(Me) (<b>6</b>) and [(<b>dtbpi</b>)­RhCl]<sub>2</sub> (<b>7</b>) were synthesized. An unexpected rearrangement of one of the formed stereoisomers of <b>6</b>, with cleavage of an N–P bond, was found. A novel phosphine-phosphonium ylide ligand (<b>8</b>) has been made accessible via chemoselective alkylation of the carbon-bound P donor of <b>dtbpi</b> to yield the phosphonium salt [<i>P</i>-CH<sub>3</sub>-dtbpi]­BF<sub>4</sub> (<b>2</b>). The ylide <b>8</b> was generated in situ by deprotonation of <b>2</b> with KHMDS. Its coordination to the PdCl­(Me) fragment led to the isolation of exclusively the <i>Z</i> isomer of [(<b>8</b>)­PdCl­(Me)] (<b><i>Z</i>-9</b>). X-ray structure analysis of [(<b>dtbpi</b>)­Rh­(NBD)]­BF<sub>4</sub> (<b>10</b>) and its dicationic analogue [(<b>H-dtbpi</b><sup><b>+</b></sup>)­Rh­(NBD)]­(BF<sub>4</sub>)­(BAr<sub>F</sub>) (<b>11</b>) revealed the structural changes provoked upon ligand backbone protonation

    An Oxidative Macrobicyclic Ring Opening of a Triptycene to a Highly Functionalized Fluorene Derivative

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    The treatment of hexamethoxytriptycenes with nitric acid leads to an unprecedented oxidative ring opening of the triptycene scaffold, resulting in a new class of fluorene derivatives with a nitroquinone unit. Preliminary investigations of the influence of chain length of alkyl substituents at the triptycene bridgeheads to the reaction have been performed, revealing that exclusively the methyl-substituted hexamethoxytriptycene does not undergo an oxidative ring opening reaction

    Stepwise Deprotonation of a Thiol-Functionalized Bis(1,2,4-triazolium) Salt as a Selective Route to Heterometallic NHC Complexes

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    Heterometallic NHC complexes have been selectively prepared at room temperature directly from an azolium salt in a two-step procedure. In the unsymmetrically substituted bis­(1,2,4-triazolium) ligand precursor, one of the <i>m</i>-xylylene-bridged triazolium units features an unprotected <i>o</i>-thiophenol substituent. This renders possible a selective deprotonation and in situ monopalladation at the NHC–thiolato unit. The obtained palladium­(II) complex possesses two pendant triazolium units as vacant binding sites. After a second deprotonation/metalation step, a heterodinuclear palladium­(II) gold­(I) complex and a heterotrinuclear palladium­(II) dicopper­(I) complex were obtained. In the latter, two metal centers are connected via a thiolato bridge

    Efficient One-Pot Synthesis of Unsymmetrical Gold(I) N-Heterocyclic Carbene Complexes and Their Use as Catalysts

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    Eleven different gold­(I) complexes of new NHC ligands were prepared in excellent yield, demonstrating the versatility of the new route to NHC complexes. While the influence of electronically different ligands on the synthesis of the catalysts was small, the catalytic activities of the products differed significantly

    Saturated Abnormal NHC–Gold(I) Complexes: Synthesis and Catalytic Activity

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    New saturated abnormal N-heterocyclic carbene complexes of gold­(I) have been prepared by a 1,3-dipolar cycloaddition of an in situ generated azomethine ylide with an isocyanogold­(I) choride. A series of different substituents on the nitrogen atom of the 1,3-dipole are tolerated without problem. Substitutents on a carbon atom of the 1,3-dipole are problematic in the case of the isocyanogold­(I) chlorides; only low yields are obtained. However, the corresponding isocyanogold­(I) iodide shows good reactivity, and these abnormal N-heterocyclic carbenes bear the substituent in a position α to the carbene carbon, as proven by a crystal structure analysis of one of the products. Some of the new saturated abnormal N-heterocyclic carbene complexes were then tested in the gold-catalyzed phenol synthesis; moderate turnover numbers of 252–380 could be reached

    Stepwise Deprotonation of a Thiol-Functionalized Bis(1,2,4-triazolium) Salt as a Selective Route to Heterometallic NHC Complexes

    No full text
    Heterometallic NHC complexes have been selectively prepared at room temperature directly from an azolium salt in a two-step procedure. In the unsymmetrically substituted bis­(1,2,4-triazolium) ligand precursor, one of the <i>m</i>-xylylene-bridged triazolium units features an unprotected <i>o</i>-thiophenol substituent. This renders possible a selective deprotonation and in situ monopalladation at the NHC–thiolato unit. The obtained palladium­(II) complex possesses two pendant triazolium units as vacant binding sites. After a second deprotonation/metalation step, a heterodinuclear palladium­(II) gold­(I) complex and a heterotrinuclear palladium­(II) dicopper­(I) complex were obtained. In the latter, two metal centers are connected via a thiolato bridge

    Halogen Bonding in Diaza-Triisopropylsilyl-Tetracene Crystals?

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    Four halogenated triisopropylsilylethynyl (TIPS)-tetracene derivatives were synthesized, their single crystal structures and optical and electronic properties were examined. Both, diiodo-TIPS-diazatetracene and dibromo-TIPS-diazatetracene showed herringbone arrangements, in which the halogen atoms are directed toward the nitrogen atoms of a neighboring molecule with slightly lower distances than the van der Waals radii between halogen and nitrogen atoms. Computations of the electrostatic potentials showed the availability and the strength of σ holes, so that we assume a weak halogen–nitrogen bonding. Tribromo-TIPS-diazatetracene delivered a 2D-brick wall structure with no sign of a halogen bonding. Dibromo-TIPS-tetracene crystallized neither in a herringbone nor in a brick wall motif. These results show that for halogenated azaacenes at least weak halogen–nitrogen interactions exist
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