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2. Tri‐ and Hexadentate Poly‐Lewis Acids – Attempts to Unravel the Complex Dynamics of Cage and Capsule Formation in Solution.

Author

Klingsiek, Maximilian J., Franke, Maurice, Walkenhorst, Simon M., Röhr, Tobias, Buth, Julian, Mix, Andreas, Lamm, Jan‐Hendrik, Neumann, Beate, Stammler, Hans‐Georg, and Mitzel, Norbert W.

Subjects
LEWIS bases, ALUMINUM hydride, LEWIS acids, EXCHANGE reactions, NUCLEAR magnetic resonance spectroscopy
Abstract

Two tri‐ and two hexadentate poly‐Lewis acids (PLAs) with calyx‐like structures of C3 symmetry containing aluminum‐ and boron‐containing Lewis acidic functions were prepared by tin‐metal exchange reactions. The triply hydrosilylated [12]annulene served as basic framework. It forms a calyx‐like structure by the stereo‐ and regioselective attachment of three SiMeCl2 groups to the planar [12]annulene. The PLA precursors were generated by attaching three or six trimethylstannylethynyl groups to the silicon atoms. Lewis acid functions were introduced using the reagents bis‐(bis(trimethylsilyl)methyl)aluminium hydride (HAl[CH(SiMe3)2]2) and catecholatochloroborane (ClBCat). The complexation behavior of the PLAs towards different Lewis bases was investigated by NMR. Bases included pyridine, polydentate nitrogen‐ and phosphorus‐containing bases. Additionally, three molecules of a bidentate phosphorus‐containing base were captured with hexadentate PLAs. Diffusion NMR experiments provided insight into the aggregation processes: some of the adducts had a significantly larger volume than expected, indicating the formation of larger adducts than the expected 1 : 1 adduct, including larger 2 : 2 adduct cages. The distances between the Lewis acid units and the steric requirement of the attached substituents determine the complexation behavior of the PLAs. Thus, the weak Lewis acidic BCat units show no (tridentate case) or a strong (hexadentate case) interaction with PMe2‐containing bases, if they can act cooperatively. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Adducts of Lewis acidic stibanes with phosphane chalcogenides.

Author

Krieft, Jonas, Koch, Hannah, Neumann, Beate, Stammler, Hans-Georg, Lamm, Jan-Hendrik, Mix, Andreas, and Mitzel, Norbert W.

Subjects
NUCLEAR magnetic resonance spectroscopy, ELEMENTAL analysis, X-ray diffraction, CHALCOGENIDES, ANGLES
Abstract

Starting from ClSbRF2 (RF = C2F5, 3,5-(CF3)2C6H3) and H(E)P(tBu)2 (E = O, S), we prepared the oxy- and sulphanediyl-bridged adducts RF2Sb(Cl)–E–(H)P(tBu)2, which are stable against the elimination of HCl. The different electron-withdrawing substituents and chalcogen bridging units influence the size of the Sb–E–P angle. ClSb(C2F5)2 and nBu3SnH react to give HSb(C2F5)2, which seems to interact weakly with H(O)P(tBu)2 in solution as observed via NMR. All products were characterised by NMR spectroscopy and all the stable ones were additionally characterised by X-ray diffraction and elemental analyses. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Host–guest chemistry of tridentate Lewis acids based on tribenzotriquinacene.

Author

Franke, Maurice, Ens, Tobin, Mix, Andreas, Neumann, Beate, Stammler, Hans-Georg, and Mitzel, Norbert W.

Subjects
LEWIS acids, HOST-guest chemistry, LEWIS bases, LEWIS acidity, NUCLEAR magnetic resonance spectroscopy, BRONSTED acids, TRIAZINES
Abstract

Flexible poly-Lewis acids (PLA) based on the tribenzotriquinacene (TBTQ) scaffold have been synthesised. Hydrosilylation of 4b,8b,12b-triallyltribenzotriquinacene and subsequent exchange of the chlorine substituents with weaker coordinating triflate groups afforded a novel triple silyl-functionalised PLA. By regioselective hydroboration of triallyl–TBTQ with various organoboranes, PLAs with different Lewis acidities were obtained. The synthesised PLAs were combined with neutral bases in host–guest experiments. DOSY NMR spectroscopy was performed to elucidate the complexation process in solution. These experiments revealed a highly dynamic interaction between the boron-functionalised PLA and triazine. However, the addition of one equivalent of tris(dimethylphosphino(methyl))phenylsilane led to the formation of a 1 : 1 adduct, which was confirmed by diffusion experiments. [ABSTRACT FROM AUTHOR]

Published
2024
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25. A Rational Approach to Tetra-Functional Photo-Switches

Author

Niermeier, Philipp, Lamm, Jan-Hendrik, Mix, Andreas, Neumann, Beate, Stammler, Hans-Georg, and Mitzel, Norbert W.

Subjects
Anthracenes, Full Paper, Cycloreversion, Full Papers, Photocyclomerization, Photo-switches, C−C-Bond Formation
Abstract

alpha,omega-Bis(1,8-dichloroanthracen-10-yl)alkanes with (CH2) n -linker units (n=1-4) were synthesized starting from 1,8-dichloroanthracen-10(9H)-one. This was transformed into anthracenes with allyl, bromomethyl and propargyl substituents in position 10; these were converted in various C-C-bond formation reactions (plus hydrogenation), leading to two anthracene units flexibly linked by alpha,omega-alkandiyl groups. 1,2-Ethandiyl- and 1,3-propandiyl-linked derivatives were functionalized with ethynyl groups in positions 1, 8, 1' and 8', and these terminally functionalized by Me3Sn groups using Me2NSnMe3. All linked bisanthracenes were subjected to UV light induced cyclomerization and a series of 9,10:9',10'-photo-cyclomers were obtained. Their thermal cycloreversion and (repeated) switchability was demonstrated. 1,3-Bis{1,8-bis[(trimethylstannyl)ethynyl]anthracen-10-yl}propane served as model compound for photo-switchable acceptor molecules and its open and closed forms were characterized by NMR and DOSY experiments.

Published
2019

26. A Neutral Methylene-linked Tin/Phosphorus Frustrated Lewis Pair

Author

Mitzel, Norbert W., Holtkamp, Philipp, Friederich, Felix, Stratmann, Erik, Mix, Andreas, Neumann, Beate, and Stammler, Hans-Georg

Abstract

The geminal frustrated Lewis pair (FLP) (F5C2)3SnCH2P(tBu)2 (2) was prepared by reacting (F5C2)3SnCl with LiCH2P(tBu)2. It is neutral and contains an extremely electronegatively substituted, but relatively soft (HSAB) acidic tin function. Its FLP-type reactivity was proven by conversion with a variety of small molecules (CO2, SO2, CS2, PhNCO, HCl, and (Ph3P)AuCl), but it shows no reaction in H/D scrambling experiments and binds CO2 reversibly, as was observed by VT-NMR spectroscopy. Compound 2 and all its adducts were completely characterised by means of multinuclear NMR spectroscopy, elemental analysis and X ray diffraction experiments. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Published
2019

35. Reversible transformation of a stable monomeric silicon(II) compound into a stable disilene by phase transfer: experimental and theoretical studies of the system [{[[([Me.sub.3Si).sub.2]N]([Me.sub.5][C.sub.5])Si}.sub.n] with n = 1, 2

Author

Jutzi, Peter, Mix, Andreas, Neumann, Beate, Rummel, Britta, Schoeller, Wolfgang W., Stammler, Hans-Georg, and Rozhenko, A.B.

Subjects
Amides -- Chemical properties, Methyl groups -- Chemical properties, Organoboron compounds -- Chemical properties, Silicon -- Chemical properties, Chemistry
Abstract

The salt ([[eta].sup.5]-pentamethylcyclopentadienyl)silicon(II) tetrakis(pentafluorophenyl)borate has reacted with lithium bis(trimethylsilyl)amide in dimethoxyethane (DME) as solvent to afford the compound [bis(trimethylsilyl)amino][pentamethylcyclopentadienyl]silicon (II) in the form of a colorless viscous oil. The reversible phase-dependent transformation of the stable monomeric silicon(II) compound into a stable disilene is caused by different stereoelectronic and steric effects, a low activation barrier for the equilibrium and the gain in entropy upon monomer formation.

Published
2009

36. Strong intramolecular Si-N interactions in the chlorosilanes [Cl.sub.3-n][H.sub.n]SiOC[H.sub.2]N[Me.sub.2] (n = 1-3)

Author

Hagemann, Michael, Mix, Andreas, Berger, Raphael J.F., Pape, Tania, and Mitzel, Nobert W.

Subjects
Nuclear magnetic resonance spectroscopy -- Usage, Organochlorine compounds -- Chemical properties, Organochlorine compounds -- Optical properties, Organosilicon compounds -- Chemical properties, Organosilicon compounds -- Structure, Organosilicon compounds -- Spectra, Quantum chemistry -- Analysis, Chemistry
Published
2008

37. C-F activation of fluorinated arenes using NHC-stabilized nickel(0) complexes: selectivity and mechanistic investigations

Author

Schaub, Thomas, Fischer, Peter, Steffen, Andreas, Braun, Thomas, Radius, Udo, and Mix, Andreas

Subjects
Nickel -- Mechanical properties, Nickel -- Chemical properties, Praseodymium -- Mechanical properties, Praseodymium -- Chemical properties, Chemistry
Abstract

The carbon-fluorine bond activations at {Ni[([super i][Pr.sub.2]Im).sub.2]} and analyzed, where the reaction are very fast and are highly regio- and chemoselective. The mechanistic studies on the activation of hexafluorobenzene and octafluoronaphthalene have detected the intermediates with the aromatic system coordinated in an [[eta].sup.2]-fashion.

Published
2008

45. Die Wirtschaft der SS

Author

Mix, Andreas

Subjects
Die Wirtschaft der SS (Book) -- Book reviews, Books -- Book reviews, Humanities, Social sciences
Published
2004

47. Alkynyl Compounds of the Rare-earth Metals

Author

Nieland, Anja, Lamm, Jan-Hendrik, Mix, Andreas, Neumann, Beate, Stammler, Hans-Georg, and Mitzel, Norbert W.

Subjects
Rare-earth metals, ligands, Nitrogen, Cations, Acetylides, Tetramethylaluminates
Abstract

Conversion of the rare-earth tetramethylaluminates [Ln(AlMe4)(3)] with phenylacetylene afforded the homoleptic alkynylaluminates [Ln{(mu-C CPh)(2)AlMe2}(3)] [Ln = Ce (1), Er(2)]. The reaction of five equivalents of phenylacetylene with the yttrium aluminate [Y(AlMe4)(3)] afforded [Y{(mu-C CPh)AlMe3}{(mu-C CPh)(2)AlMe2}(2)] (3). The cationic yttrium complex [(TMTAC)(2)YMe2][AlMe4] (4) (TMTAC = 1,3,5-trimethyl-1,3,5triazacyclohexane) was reacted with phenylacetylene to give the product [(TMTAC)(2)Y(C CPh)(2)][Me2Al(C CPh)(2)] (5), in which two methyl groups of each, the cation and the anion, were substituted by phenylacetylide groups. Under the same conditions as for the synthesis of compound 5, the holmium analogue reveals different reactivity in forming a neutral alkynyl complex [(TMTAC)(2)Ho(C CPh)(3)] (6). The introduction of 1,8-diethynylanthracene to 4 leads to a structural very similar complex [(TMTAC)(2)Ho(mu-1,8-diethynylanthracene)(3)] (7) and offers the same reactivity as observed for the synthesis of 6. All compounds were characterized by X-ray diffraction experiments. Compounds 1-3 and 5 were also characterized by NMR and elemental analyses.

Published
2014

50. Politik mit der Vergangenheit: VOM NUTZEN UND NACHTEIL DER GESCHICHTSPOLITIK FÜR DIE POLNISCHE REGIERUNG.

Author

Mix, Andreas

Abstract

Copyright of Journal for Human Rights / Zeitschrift für Menschenrechte is the property of Wochenschau Verlag GmbH and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2018
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