@article{ZottnickSprengerFinzeetal.2021, author = {Zottnick, Sven H. and Sprenger, Jan A. P. and Finze, Maik and M{\"u}ller-Buschbaum, Klaus}, title = {Statistic Replacement of Lanthanide Ions in Bis-salicylatoborate Coordination Polymers for the Deliberate Control of the Luminescence Chromaticity}, series = {ChemistryOpen}, volume = {10}, journal = {ChemistryOpen}, number = {2}, doi = {10.1002/open.202000251}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-239953}, pages = {164 -- 170}, year = {2021}, abstract = {Based on the strand-like coordination polymer (CP) type \(^{1}\)\(_{∞}\)[Ln(BSB)\(_{3}\)(py)\(_{2}\)], [BSB]-=bis-salicylatoborate anion, mixed Eu/Tb-containing compounds of the constitution \(^{1}\)\(_{∞}\)[Eu\(_{x}\)Tb\(_{1-x}\)(BSB)\(_{3}\)(py)\(_{2}\)] were synthesised ionothermally for a phase width of (x=0.25-0.75) and characterized regarding structure and optical properties. Previously, known only for other lanthanides, the mixed 1D-Eu/Tb-CPs show excellent options for statistic replacement of the Ln-cations during synthesis yielding solid solutions. The products are highly luminescent, with the chromaticity being a direct function of the amount of the respective Ln-ions. Corresponding to an overall addition of emission intensities, the green Tb\(^{3+}\) emission and the red Eu\(^{3+}\) emission allow for a chromaticity control that also includes yellow emission. Control of the luminescence colour renders them suitable examples of the versatility of statistic replacement of metal ions in coordination chemistry. In addition, crystallization of [EMIm]\(_{2}\)[YCl\(_{5}\)(py)] illuminates possible other products of the ionothermal reactions of [EMIm][BSB] with LnCl\(_{3}\) constituted by components not being part of the main CPs.}, language = {en} } @article{ZhangFriedrichMarder2022, author = {Zhang, Xiaolei and Friedrich, Alexandra and Marder, Todd B.}, title = {Copper-Catalyzed Borylation of Acyl Chlorides with an Alkoxy Diboron Reagent: A Facile Route to Acylboron Compounds}, series = {Chemistry—A European Journal}, volume = {28}, journal = {Chemistry—A European Journal}, number = {42}, doi = {10.1002/chem.202201329}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318318}, year = {2022}, abstract = {Herein, the copper-catalyzed borylation of readily available acyl chlorides with bis(pinacolato)diboron, (B\(_{2}\)pin\(_{2}\)) or bis(neopentane glycolato)diboron (B\(_{2}\)neop\(_{2}\)) is reported, which provides stable potassium acyltrifluoroborates (KATs) in good yields from the acylboronate esters. A variety of functional groups are tolerated under the mild reaction conditions (room temperature) and substrates containing different carbon-skeletons, such as aryl, heteroaryl and primary, secondary, tertiary alkyl are applicable. Acyl N-methyliminodiacetic acid (MIDA) boronates can also been accessed by modification of the workup procedures. This process is scalable and also amenable to the late-stage conversion of carboxylic acid-containing drugs into their acylboron analogues, which have been challenging to prepare previously. A catalytic mechanism is proposed based on in situ monitoring of the reaction between p-toluoyl chloride and an NHC-copper(I) boryl complex as well as the isolation of an unusual lithium acylBpinOBpin compound as a key intermediate.}, language = {en} } @article{ZhangRadackiBraunschweigetal.2021, author = {Zhang, Fangyuan and Radacki, Krzysztof and Braunschweig, Holger and Lambert, Christoph and Ravat, Prince}, title = {Zinc-[7]helicenocyanine and its discrete π-stacked homochiral Dimer}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, doi = {10.1002/anie.202109380}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256534}, pages = {23656-23660}, year = {2021}, abstract = {In this communication, we demonstrate a novel approach to prepare a discrete dimer of chiral phthalocyanine (Pc) by exploiting the flexible molecular geometry of helicenes, which enables structural interlocking and strong aggregation tendency of Pcs. Synthesized [7]helicene-Pc hybrid molecular structure, zinc-[7]helicenocyanine (Zn-7HPc), exclusively forms a stable dimeric pair consisting of two homochiral molecules. The dimerization constants were estimated to be as high as 8.96×10\(^6\) M\(^{-1}\) and 3.42×107 M\(^{-1}\) in THF and DMSO, respectively, indicating remarkable stability of dimer. In addition, Zn\(^{-7}\)HPc exhibited chiral self-sorting behavior, which resulted in preferential formation of a homochiral dimer also in the racemic sample. Two phthalocyanine subunits in the dimeric form strongly communicate with each other as revealed by a large comproportionation constant and observation of an IV-CT band for the thermodynamically stable mixed-valence state.}, language = {en} } @article{ZhangLiuWangetal.2022, author = {Zhang, Chonghe and Liu, Xiaocui and Wang, Junyi and Ye, Qing}, title = {A Three-Dimensional Inorganic Analogue of 9,10-Diazido-9,10-Diboraanthracene: A Lewis Superacidic Azido Borane with Reactivity and Stability}, series = {Angewandte Chemie}, volume = {61}, journal = {Angewandte Chemie}, number = {36}, doi = {10.1002/anie.202205506}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318322}, year = {2022}, abstract = {Herein, we report the facile synthesis of a three-dimensional (3D) inorganic analogue of 9,10-diazido-9,10-dihydrodiboraantracene, which turned out to be a monomer in both the solid and solution state, and thermally stable up to 230 °C, representing a rare example of azido borane with boosted Lewis acidity and stability in one. Apart from the classical acid-base and Staudinger reactions, E-H bond activation (E=B, Si, Ge) was investigated. While the reaction with B-H (9-borabicyclo[3.3.1]nonane) led directly to the 1,1-addition on N\(_{α}\) upon N\(_{2}\) elimination, the Si-H (Et\(_{3}\)SiH, PhMe\(_{2}\)SiH) activation proceeded stepwise via 1,2-addition, with the key intermediates 5\(_{int}\) and 6\(_{int}\) being isolated and characterized. In contrast, the cooperative Ge-H was reversible and stayed at the 1,2-addition step.}, language = {en} } @article{ZapfRadiusFinze2021, author = {Zapf, Ludwig and Radius, Udo and Finze, Maik}, title = {1,3-bis(tricyanoborane)imidazoline-2-ylidenate anion - a ditopic dianionic N-heterocyclic carbene ligand}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {33}, doi = {10.1002/anie.202105529}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256498}, pages = {17974-17980}, year = {2021}, abstract = {The 1,3-bis(tricyanoborane)imidazolate anion 1 was obtained in high yield from lithium imidazolate and B(CN)\(_3\)-pyridine adduct. Anion 1 is chemically very robust and thus allowed the isolation of the corresponding H\(_5\)O\(_2\)\(^+\) salt. Furthermore, monoanion 1 served as starting species for the novel dianionic N-heterocyclic carbene (NHC), 1,3-bis(tricyanoborane)imidazoline-2-ylidenate anion 3 that acts as ditopic ligand via the carbene center and the cyano groups at boron. First reactions of this new NHC 3 with methyl iodide, elemental selenium, and [Ni(CO)\(_4\)] led to the methylated imidazolate ion 4, the dianionic selenium adduct 5, and the dianionic nickel tricarbonyl complex 6. These NHC derivatives provide a first insight into the electronic and steric properties of the dianionic NHC 3. Especially the combination of properties, such as double negative charge, different coordination sites, large buried volume and good σ-donor and π-acceptor ability, make NHC 3 a unique and promising ligand and building block.}, language = {en} } @article{ZapfPetersBertermannetal.2022, author = {Zapf, Ludwig and Peters, Sven and Bertermann, R{\"u}diger and Radius, Udo and Finze, Maik}, title = {Tricyanoborane-Functionalized Anionic N-Heterocyclic Carbenes: Adjustment of Charge and Stereo-Electronic Properties}, series = {Chemistry - A European Journal}, volume = {28}, journal = {Chemistry - A European Journal}, number = {39}, doi = {10.1002/chem.202200275}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287200}, year = {2022}, abstract = {The 1-methyl-3-(tricyanoborane)imidazolin-2-ylidenate anion (2) was obtained in high yield by deprotonation of the B(CN)3-methylimidazole adduct 1. Regarding charge and stereo-electronic properties, anion 2 closes the gap between well-known neutral NHCs and the ditopic dianionic NHC, the 1,3-bis(tricyanoborane)imidazolin-2-ylidenate dianion (IIb). The influence of the number of N-bonded tricyanoborane moieties on the σ-donating and π-accepting properties of NHCs was assessed by quantum chemical calculations and verified by experimental data on 2, IIb, and 1,3-dimethylimidazolin-2-ylidene (IMe, IIa). Therefore NHC 2, which acts as a ditopic ligand via the carbene center and the cyano groups, was reacted with alkyl iodides, selenium, and [Ni(CO)\(_{4}\)] yielding alkylated imidazoles 3 and 4, the anionic selenium adduct 5, and the anionic nickel tricarbonyl complex 8, respectively. The results of this study prove that charge, number of coordination sites, buried volume (\%V\(_{bur}\)) and σ-donor and π-acceptor abilities of NHCs can be effectively fine-tuned via the number of tricyanoborane substituents.}, language = {en} } @article{ZapfFinze2021, author = {Zapf, Ludwig and Finze, Maik}, title = {The crystal structure of poly[(μ \(_3\)-imidazolato-κ \(^3\) N:N:N′)(tetrahydrofuran- κ \(^1\) O)lithium(I)], C\(_7\)H\(_{11}\)LiN\(_2\)O}, series = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures}, volume = {236}, journal = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures}, number = {5}, doi = {10.1515/ncrs-2021-0192}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260745}, pages = {1007-1009}, year = {2021}, abstract = {C\(_7\)H\(_{11}\)LiN\(_2\)O, monoclinic, P2\(_1\)/c (no. 14), a = 8.9067(1) angstrom, b = 8.6975(1) angstrom, c = 10.2398(1) angstrom, beta = 101.900(3)degrees, V = 770.491(15) angstrom(3), Z = 4, R-gt (F) = 0.0338, wR(ref) (F\(^2\)) = 0.0925, T = 100 K.}, language = {en} } @phdthesis{Zapf2023, author = {Zapf, Ludwig}, title = {Novel Borane- and Phosphorane- Functionalized Anionic Carbene Ligands}, doi = {10.25972/OPUS-32078}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-320781}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {N-heterocyclic carbenes (NHC) are utilized for the stabilization of reactive compounds, for the activation of strong bonds, and as ligands in transition metal chemistry. In contrast to neutral NHCs, few examples of anionic or even dianionic NHCs are known. One approach for the synthesis of anionic carbenes is the deprotonation of neutral or anionic precursors, bearing Lewis acids instead of alkyl or aryl substituents. Following this strategy, novel anionic and dianionic NHCs, featuring weakly coordinating fluorinated borane and phosphorane substituents or coordinating tricyanoborane substituents were synthesized within the scope of this thesis. These carbenes possess unprecedented stabilities compared to related species. Furthermore, their electronic and steric properties can be directly adjusted by the type of Lewis acid attached. Their potential as ligands with highly shielding weakly coordinating substituents next to the carbene coordination center was demonstrated by the syntheses of the respective NHC selenium adducts and NHC gold(I) complexes. In contrast anionic NHCs with coordinating tricyanoborane moieties have an outstanding potential as ditopic ligands with coordination being possible at the carbene center and via the cyano groups. Their beneficial ligand properties were demonstrated by the syntheses of the respective NHC selenium adducts and NHC nickeltricarbonyl complexes. The combination of electronic properties, the large buried volume, the negative charge, the possibility to act as ditopic or ligands with weakly coordinating groups, and the ease of accessibility render borane- and phosphorane functionalized NHCs unique novel ligands. A further project of this PhD thesis deals with the steric properties of Lewis acids. Therefore, an easy-to-apply model was designed to quantify the steric demand of Lewis acids. Using the results of this evaluation, a second model was developed which judges the steric repulsion in Lewis acid/base adduct formation for arbitrary sets of acids and bases.}, subject = {Komplexe}, language = {en} } @phdthesis{Ye2012, author = {Ye, Qing}, title = {Synthesis and Investigation of Borylene Complexes: from Borylene Transfer to Borylene Catenation}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-71443}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2012}, abstract = {Im Rahmen dieser Arbeit wurde das Spektrum des Borylentransfers ausgeweitet, indem {\"U}bergangsmetall Alkinylkomplexe und Metall-Kohlenstoff-Doppelbindungen als Borylen-Akzeptoren eingeschlossen wurden. Neben der Salzeliminierung, Halogenidabstraktion und Dehydrierung, wurde eine neuartige Syntheseroute zu terminalen Borylenkomplexen durch Salz- und Silylhalogenideliminierung etabliert. Mithilfe dieser Strategie gelang die Darstellung von [(OC)3(Me3P)Fe=BDur], ein seltenes Beispiel f{\"u}r einen neutralen Arylborylenkomplex. Im Speziellen hat diese Verbindung ein großes Anwendungspotenzial f{\"u}r Metathesereaktionen und die Funktionalisierung von polycyclischen aromatischen Kohlenwasserstoffen, wie z. B. Naphthalin, gezeigt. Außerdem konnte ein Eisen-Bis(borylen)-Komplex [(OC)3Fe(BDur){BN(SiMe3)2}] durch einen Phosphan-Borylen-Austausch dargestellt werden. Ausgehend von diesem Komplex gelang die Darstellung von 1,4-Diboracyclohexadien bzw. des ersten 1,4-Dibora-1,3-Butadien-Komplexes, wodurch eine neue Art von Borylentransfer etabliert werden konnte. H{\"o}chst interessant ist es, dass der Transfer von weiteren Borylen-Einheiten in die Koordinationssph{\"a}re des Eisenatoms zu einer kontrollierten Borylen-Verkettung gef{\"u}hrt hat.}, subject = {Borylene}, language = {en} } @phdthesis{WuertembergerPietsch2017, author = {W{\"u}rtemberger-Pietsch, Sabrina}, title = {Anionic and Neutral Lewis-Base Adducts of Diboron(4) Compounds}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-136321}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2017}, abstract = {Anionic Adducts Sp2-sp3 tetraalkoxy diboron compounds have gained attention due to the development of new, synthetically useful catalytic reactions either with or without transition-metals. Lewis-base adducts of the diboron(4) compounds were suggested as possible intermediates in Cu catalyzed borylation reactions some time ago. However, intermolecular adducts of tetraalkoxy diboron compounds have not been studied yet in great detail. In preliminary studies, we have synthesized a series of anionic sp2-sp3 adducts of B2pin2 with alkoxy-groups (L = [OMe]-, [OtBu]-), a phenoxy-group (L = [4-tBuC6H4O]-) and fluoride (L = [F]-, with [nBu4N]+ as the counter ion) as Lewis-bases. Neutral Adducts Since their isolation and characterization, applications of N-heterocyclic carbenes (NHCs) and related molecules, e.g., cyclic alkylaminocarbenes (CAACs) and acyclic diaminocarbenes (aDCs), have grown rapidly. Their use as ligands in homogeneous catalysis and directly in organocatalysis, including recently developed borylation reactions, is now well established. Recently, several examples of ring expansion reactions (RER) involving NHCs were reported to take place at elevated temperatures, involving Be, B, and Si. Furthermore, preliminary studies in the group of Marder et al. showed the presence of neutral sp2-sp3 diboron compounds with B2pin2 and the NHC Cy2Im. In this work, we focused on the synthesis and characterization of further neutral sp2-sp3 as well as sp3-sp3 diboron adducts with B2cat2 and B2neop2 and different NHCs. Whereas the mono-NHC adduct is stable for several hours at temperatures up to 60 °C, the bis-NHC adducts undergo thermally induced rearrangement to form the ring expanded products compound 26 and 27. B2neop2 is much more reactive than B2cat2 giving ring expanded product 29 at room temperature in quantitative yields, demonstrating that NHC ring expansion and B-B bond cleavage can be very facile processes. Whereas the mono-NHC adduct is stable for several hours at temperatures up to 60 °C, the bis-NHC adducts undergo thermally induced rearrangement to form the ring expanded products compound 26 and 27. B2neop2 is much more reactive than B2cat2 giving ring expanded product 29 at room temperature in quantitative yields, demonstrating that NHC ring expansion and B-B bond cleavage can be very facile processes.}, subject = {Addukt}, language = {en} } @article{WuRoldaoRauchetal.2022, author = {Wu, Zhu and Roldao, Juan Carlos and Rauch, Florian and Friedrich, Alexandra and Ferger, Matthias and W{\"u}rthner, Frank and Gierschner, Johannes and Marder, Todd B.}, title = {Pure Boric Acid Does Not Show Room-Temperature Phosphorescence (RTP)}, series = {Angewandte Chemie}, volume = {61}, journal = {Angewandte Chemie}, number = {15}, doi = {10.1002/anie.202200599}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318308}, year = {2022}, abstract = {Boric acid (BA) has been used as a transparent glass matrix for optical materials for over 100 years. However, recently, apparent room-temperature phosphorescence (RTP) from BA (crystalline and powder states) was reported (Zheng et al., Angew. Chem. Int. Ed. 2021, 60, 9500) when irradiated at 280 nm under ambient conditions. We suspected that RTP from their BA sample was induced by an unidentified impurity. Our experimental results show that pure BA synthesized from B(OMe)\(_{3}\) does not luminesce in the solid state when irradiated at 250-400 nm, while commercial BA indeed (faintly) luminesces. Our theoretical calculations show that neither individual BA molecules nor aggregates would absorb light at >175 nm, and we observe no absorption of solid pure BA experimentally at >200 nm. Therefore, it is not possible for pure BA to be excited at >250 nm even in the solid state. Thus, pure BA does not display RTP, whereas trace impurities can induce RTP.}, language = {en} } @article{WuNitschMarder2021, author = {Wu, Zhu and Nitsch, J{\"o}rn and Marder, Todd B.}, title = {Persistent room-temperature phosphorence from purely organic molecules and multi-component systems}, series = {Advanced Optical Materials}, volume = {9}, journal = {Advanced Optical Materials}, number = {20}, doi = {doi.org/10.1002/adom.202100411}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256415}, year = {2021}, abstract = {Recently, luminophores showing efficient room-temperature phosphorescence (RTP) have gained tremendous interest due to their numerous applications. However, most phosphors are derived from transition metal complexes because of their intrinsic fast intersystem crossing (ISC) induced by strong spin-orbit coupling (SOC) constants of the heavy metal. Metal-free RTP materials are rare and have become a promising field because they are inexpensive and environmentally friendly. This review summarizes organic molecular materials with long triplet lifetimes at room temperature from the perspective of whether they stem from a molecular or multi-component system. Among purely organic phosphors, heteroatoms are usually introduced into the backbone in order to boost the singlet-triplet ISC rate constant. In multi-component systems, useful strategies such as host-guest, polymer matrix, copolymerization, and supramolecular assembly provide a rigid matrix to restrict nonradiative pathways thus realizing ultralong RTP.}, language = {en} } @article{WuDinkelbachKerneretal.2022, author = {Wu, Zhu and Dinkelbach, Fabian and Kerner, Florian and Friedrich, Alexandra and Ji, Lei and Stepanenko, Vladimir and W{\"u}rthner, Frank and Marian, Christel M. and Marder, Todd B.}, title = {Aggregation-Induced Dual Phosphorescence from (o-Bromophenyl)-Bis(2,6-Dimethylphenyl)Borane at Room Temperature}, series = {Chemistry—A European Journal}, volume = {28}, journal = {Chemistry—A European Journal}, number = {30}, doi = {10.1002/chem.202200525}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318297}, year = {2022}, abstract = {Designing highly efficient purely organic phosphors at room temperature remains a challenge because of fast non-radiative processes and slow intersystem crossing (ISC) rates. The majority of them emit only single component phosphorescence. Herein, we have prepared 3 isomers (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. Based on theoretical calculations and crystal structure analysis of o-BrTAB, the short lifetime component is ascribed to the T\(^M_1\) state of the monomer which emits the higher energy phosphorescence. The long-lived, lower energy phosphorescence emission is attributed to the T\(^A_1\) state of an aggregate, with multiple intermolecular interactions existing in crystalline o-BrTAB inhibiting nonradiative decay and stabilizing the triplet states efficiently.}, language = {en} } @phdthesis{Wu2022, author = {Wu, Zhu}, title = {Room Temperature Phosphorescence (RTP): Experimental And Theoretical Studies on Boron-Containing Materials}, doi = {10.25972/OPUS-26084}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260844}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2022}, abstract = {Persistent room temperature phosphorescent (RTP) luminophores have gained remarkable interest recently for a number of applications in security printing, OLEDs, optical storage, time-gated biological imaging and oxygen sensors. We report the first persistent RTP with lifetimes up to 0.5 s from simple triarylboranes which have no lone pairs. We also have prepared 3 isomeric (o, m, p-bromophenyl)-bis(2,6-dimethylphenyl)boranes. Among the 3 isomers (o-, m- and p-BrTAB) synthesized, the ortho-one is the only one which shows dual phosphorescence, with a short lifetime of 0.8 ms and a long lifetime of 234 ms in the crystalline state at room temperature. At last, we checked the RTP properties from the boric acid. We found that the pure boric acid does not show RTP in the solid state.}, language = {en} } @article{WitteArrowsmithLamprechtetal.2023, author = {Witte, Robert and Arrowsmith, Merle and Lamprecht, Anna and Schorr, Fabian and Krummenacher, Ivo and Braunschweig, Holger}, title = {C-C and C-N Bond Activation, Lewis-Base Coordination and One- and Two-Electron Oxidation at a Linear Aminoborylene}, series = {Chemistry - A European Journal}, volume = {29}, journal = {Chemistry - A European Journal}, number = {16}, doi = {10.1002/chem.202203663}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312491}, year = {2023}, abstract = {A cyclic alkyl(amino)carbene (CAAC)-stabilized dicoordinate aminoborylene is synthesized by the twofold reduction of a [(CAAC)BCl\(_{2}\)(TMP)] (TMP=2,6-tetramethylpiperidyl) precursor. NMR-spectroscopic, X-ray crystallographic and computational analyses confirm the cumulenic nature of the central C=B=N moiety. Irradiation of [(CAAC)B(TMP)] (2) resulted in an intramolecular C-C bond activation, leading to a doubly-fused C\(_{10}\)BN heterocycle, while the reaction with acetonitrile resulted in an aryl migration from the CAAC to the acetonitrile nitrogen atom, concomitant with tautomerization of the latter to a boron-bound allylamino ligand. One-electron oxidation of 2 with CuX (X=Cl, Br) afforded the corresponding amino(halo)boryl radicals, which were characterized by EPR spectroscopy and DFT calculations. Placing 2 under an atmosphere of CO afforded the tricoordinate (CAAC,CO)-stabilized aminoborylene. Finally, the twofold oxidation of 2 with chalcogens led, in the case of N\(_{2}\)O and sulfur, to the splitting of the B-C\(_{CAAC}\) bond and formation of the 2,4-diamino-1,3,2,4-dichalcogenadiboretanes and CAAC-chalcogen adducts, whereas with selenium a monomeric boraselenone was isolated, which showed some degree of B-Se multiple bonding.}, language = {en} } @article{WirthensohnFinze2020, author = {Wirthensohn, Raphael and Finze, Maik}, title = {The crystal structure of trimethylsulfonium tris(trifluoromethylsulfonyl)methanide, C\(_7\)H\(_9\)F\(_9\)O\(_6\)S\(_4\)}, series = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures}, volume = {236}, journal = {Zeitschrift f{\"u}r Kristallographie - New Crystal Structures}, number = {2}, doi = {10.1515/ncrs-2020-0612}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-231358}, pages = {417-419}, year = {2020}, abstract = {C\(_7\)H\(_9\)F\(_9\)O\(_6\)S\(_4\), orthorhombic, P2\(_1\)2\(_1\)2\(_1\) (no. 19), a = 8.80180(10) {\AA}, b= 10.96580(10) {\AA}, c = 16.91360(10) {\AA},V= 1632.48(3) {\AA}\(^3\), Z= 4, R\(_{gt}\)(F) = 0.0222, wR\(_{ref}\)(F\(^2\)) = 0.0604, T = 100 K.}, language = {en} } @article{WildervanckHechtNowakKrol2022, author = {Wildervanck, Martijn J. and Hecht, Reinhard and Nowak-Kr{\´o}l, Agnieszka}, title = {Synthesis and strong solvatochromism of push-pull thienylthiazole boron complexes}, series = {Molecules}, volume = {27}, journal = {Molecules}, number = {17}, issn = {1420-3049}, doi = {10.3390/molecules27175510}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-286186}, year = {2022}, abstract = {The solvatochromic behavior of two donor-π bridge-acceptor (D-π-A) compounds based on the 2-(3-boryl-2-thienyl)thiazole π-linker and indandione acceptor moiety are investigated. DFT/TD-DFT calculations were performed in combination with steady-state absorption and emission measurements, along with electrochemical studies, to elucidate the effect of two different strongly electron-donating hydrazonyl units on the solvatochromic and fluorescence behavior of these compounds. The Lippert-Mataga equation was used to estimate the change in dipole moments (Δµ) between ground and excited states based on the measured spectroscopic properties in solvents of varying polarity with the data being supported by theoretical studies. The two asymmetrical D-π-A molecules feature strong solvatochromic shifts in fluorescence of up to ~4300 cm\(^{-1}\) and a concomitant change of the emission color from yellow to red. These changes were accompanied by an increase in Stokes shift to reach values as large as ~5700-5800 cm\(^{-1}\). Quantum yields of ca. 0.75 could be observed for the N,N-dimethylhydrazonyl derivative in nonpolar solvents, which gradually decreased along with increasing solvent polarity, as opposed to the consistently reduced values obtained for the N,N-diphenylhydrazonyl derivative of up to ca. 0.20 in nonpolar solvents. These two push-pull molecules are contrasted with a structurally similar acceptor-π bridge-acceptor (A-π-A) compound.}, language = {en} } @article{WeiserCuiDewhurstetal.2023, author = {Weiser, Jonas and Cui, Jingjing and Dewhurst, Rian D. and Braunschweig, Holger and Engels, Bernd and Fantuzzi, Felipe}, title = {Structure and bonding of proximity-enforced main-group dimers stabilized by a rigid naphthyridine diimine ligand}, series = {Journal of Computational Chemistry}, volume = {44}, journal = {Journal of Computational Chemistry}, number = {3}, doi = {10.1002/jcc.26994}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312586}, pages = {456 -- 467}, year = {2023}, abstract = {The development of ligands capable of effectively stabilizing highly reactive main-group species has led to the experimental realization of a variety of systems with fascinating properties. In this work, we computationally investigate the electronic, structural, energetic, and bonding features of proximity-enforced group 13-15 homodimers stabilized by a rigid expanded pincer ligand based on the 1,8-naphthyridine (napy) core. We show that the redox-active naphthyridine diimine (NDI) ligand enables a wide variety of structural motifs and element-element interaction modes, the latter ranging from isolated, element-centered lone pairs (e.g., E = Si, Ge) to cases where through-space π bonds (E = Pb), element-element multiple bonds (E = P, As) and biradical ground states (E = N) are observed. Our results hint at the feasibility of NDI-E2 species as viable synthetic targets, highlighting the versatility and potential applications of napy-based ligands in main-group chemistry.}, language = {en} } @article{WeiWangYangetal.2023, author = {Wei, Yuxiang and Wang, Junyi and Yang, Weiguang and Lin, Zhenyang and Ye, Qing}, title = {Boosting Ring Strain and Lewis Acidity of Borirane: Synthesis, Reactivity and Density Functional Theory Studies of an Uncoordinated Arylborirane Fused to o-Carborane}, series = {Chemistry - A European Journal}, volume = {29}, journal = {Chemistry - A European Journal}, number = {5}, doi = {10.1002/chem.202203265}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-312089}, year = {2023}, abstract = {Among the parent borirane, benzoborirene and ortho-dicarbadodecaborane-fused borirane, the latter possesses the highest ring strain and the highest Lewis acidity according to our density functional theory (DFT) studies. The synthesis of this class of compounds is thus considerably challenging. The existing examples require either a strong π-donating group or an extra ligand for B-coordination, which nevertheless suppresses or completely turns off the Lewis acidity. The title compound, which possesses both features, not only allows the 1,2-insertion of P=O, C=O or C≡N to proceed under milder conditions, but also enables the heretofore unknown dearomative 1,4-insertion of Ar-(C=O)- into a B-C bond. The fusion of strained molecular systems to an o-carborane cage shows great promise for boosting both the ring strain and acidity.}, language = {en} } @unpublished{WangArrowsmithBraunschweigetal.2017, author = {Wang, Sunewang Rixin and Arrowsmith, Merle and Braunschweig, Holger and Dewhurst, Rian and Paprocki, Valerie and Winner, Lena}, title = {CuOTf-mediated intramolecular diborene hydroarylation}, series = {Chemical Communications}, journal = {Chemical Communications}, doi = {10.1039/C7CC07371B}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-154055}, year = {2017}, abstract = {Upon complexation to CuOTf, a PMe\(_3\)-stabilized bis(9-anthryl) diborene slowly undergoes an intramolecular hydroarylation reaction at room temperature. Subsequent triflation of the B-H bond with CuOTf, followed by a PMe\(_3\) transfer, finally yields a cyclic sp\(^2\)-sp\(^3\) boryl-substituted boronium triflate salt.}, language = {en} } @unpublished{WangArrowsmithBraunschweigetal.2017, author = {Wang, Sunewang Rixin and Arrowsmith, Merle and Braunschweig, Holger and Dewhurst, Rian and D{\"o}mling, Michael and Mattock, James and Pranckevicius, Conor and Vargas, Alfredo}, title = {Monomeric 16-Electron π-Diborene Complexes of Zn(II) and Cd(II)}, series = {Journal of the American Chemical Society}, journal = {Journal of the American Chemical Society}, doi = {10.1021/jacs.7b06644}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-153058}, year = {2017}, abstract = {Despite the prevalence of stable π-complexes of most d\(^{10}\) metals, such as Cu(I) and Ni(0), with ethylene and other olefins, complexation of d\(^{10}\) Zn(II) to simple olefins is too weak to form isolable complexes due to the metal ion's limited capacity for π-backdonation. By employing more strongly donating π- ligands, namely neutral diborenes with a high-lying π(B=B) or- bital, monomeric 16-electron M(II)-diborene (M = Zn, Cd) π- complexes were synthesized in good yields. Metal-B2 π- interactions in both the solid and solution state were confirmed by single-crystal X-ray analyses and their solution NMR and UV-vis absorption spectroscopy, respectively. The M(II) centers adopt a trigonal planar geometry and interact almost symmetrically with both boron atoms. The MB2 planes significantly twist out of the MX\(_2\) planes about the M-centroid(B-B) vector, with angles rang- ing from 47.0° to 85.5°, depending on the steric interactions be- tween the diborene ligand and the MX\(_2\) fragment.}, language = {en} } @unpublished{WangArrowsmithBoehnkeetal.2017, author = {Wang, Sunewang R. and Arrowsmith, Merle and B{\"o}hnke, Julian and Braunschweig, Holger and Dellermann, Theresa and Dewhurst, Rian D. and Kelch, Hauke and Krummenacher, Ivo and Mattock, James D. and M{\"u}ssig, Jonas H. and Thiess, Torsten and Vargas, Alfredo and Zhang, Jiji}, title = {Engineering a Small HOMO-LUMO Gap and Intramolecular B-B Hydroarylation by Diborene/Anthracene Orbital Intercalation}, series = {Angewandte Chemie, International Edition}, volume = {56}, journal = {Angewandte Chemie, International Edition}, number = {27}, doi = {10.1002/anie.201704063}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148126}, pages = {8009-8013}, year = {2017}, abstract = {The diborene 1 was synthesized by reduction of a mixture of 1,2-di-9-anthryl-1,2-dibromodiborane(4) (6) and trimethylphosphine with potassium graphite. The X-ray structure of 1 shows the two anthryl rings to be parallel and their π(C\(_{14}\)) systems perpendicular to the diborene π(B=B) system. This twisted conformation allows for intercalation of the relatively high-lying π(B=B) orbital and the low-lying π* orbital of the anthryl moiety with no significant conjugation, resulting in a small HOMO-LUMO gap (HLG) and ultimately an unprecedented anthryl B-B bond hydroarylation. The HLG of 1 was estimated to be 1.57 eV from the onset of the long wavelength band in its UV-vis absorption spectrum (THF, λ\(_{onset}\) = 788 nm). The oxidation of 1 with elemental selenium afforded diboraselenirane 8 in quantitative yield. By oxidative abstraction of one phosphine ligand by another equivalent of elemental selenium, the B-B and C\(^1\)-H bonds of 8 were cleaved to give the cyclic 1,9-diboraanthracene 9.}, language = {en} } @phdthesis{Walfort2001, author = {Walfort, Bernhard}, title = {Novel dianionic sulfur ylides and related compounds}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-1181274}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2001}, abstract = {Priority task of the thesis was to replace oxygen atoms in sulfur oxoanions SOnm- or imido groups in sulfur polyimido anions S(NR)nm- isoelectronically by R2C-methylene groups. This would open a wide avenue to new target molecules containing a formally double bonded carbon next to formally double bonded nitrogen atoms in highly charged sulfur-centred anions like S(CR2)x(NR)ym-. They clearly are reminiscent to sulfur ylides. Both, alkylendiimidosulfites and alkylentriimidosulfates are accessible via deprotonaton of the corresponding alkyldiimidosulfinates and alkyltriimidosulfonates with methyllithium. The reactivity of the novel compounds is dominated by the carbanionic centre. Addition reactions to another SN formal doubble bond are feasible and are leading to the yet unknown imidoanalogues compounds alkyl-bis-(diimidosulfinates) and alkyl-bis-(triimidosulfonates).}, subject = {Schwefelylide}, language = {en} } @article{WaelbroeckTastenoyCamusetal.1989, author = {Waelbroeck, M. and Tastenoy, M. and Camus, J. and Christophe, J. and Strohmann, C. and Linoh, H. and Zilch, H. and Tacke, Reinhold and Mutschler, E. and Lambrecht, G.}, title = {Binding and functional properties of antimuscarinics of the hexocyclium/sila-hexocyclium and hexahydro-diphenidol/hexahydro-sila-diphenidol type to muscarinic receptor subtypes}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-63944}, year = {1989}, abstract = {l In an attempt to assess the structural requirements for the musearlnie receptor selectivity of hexahydro-diphenidol (hexahydro-difenidol) and hexahydro-sila-diphenidol (hexahydro-sila-difenidol), a serles of structurally related C/Si pairs were investigated, along with atropine, pirenzepine and methoctramine, for their binding affinities in NB-OK 1 cells as well as in rat heart and pancreas. 2 The action of these antagonists at musearlnie receptors mediating negative inotropic responses in guinea-pig atrla and ileal contractions has also been assessed. 3 Antagonist binding data indicated that NB-OK 1 cells (M\(_1\) type) as weil as rat heart (cardiac type) and pancreas (glandularjsmooth muscle type) possess different muscarinic receptor subtypes. 4 A highly significant correlation was found between the binding affinities of the antagonists to muscarinic receptors in rat heart and pancreas, respectively, and the affinities to muscarinic receptors in guinea-pig atria and ileum. This implies that the musearlnie binding sites in rat heart and the receptors in guinea-pig atrla are essentially similar, but different from those in pancreas and ileum. 5 The antimuscarinic potency of hexahydro-diphenidol and hexahydro-sila-diphenidol at the three subtypes was inftuenced differently by structural modifications (e.g. quaternization). Different selectivity profiles for the antagonists were obtained, which makes these compounds useful tools to investigate further muscarinic receptor heterogeneity. lndeed, the tertiary analogues hexahydrodiphenidol (HHD) and hexahydro-sila-diphenidol (HHSiD) bad an M\(_1\) = glandularjsmooth muscle > cardiac selectivity profile, whereas the quaternary analogues HHD methiodide and HHSiD methiodide were M\(_1\) preferring (M\(_1\) > glandularjsmooth muscle, cardiac).}, subject = {Anorganische Chemie}, language = {en} } @article{WaelbroeckCamusTastenoyetal.1992, author = {Waelbroeck, M. and Camus, J. and Tastenoy, M. and Mutschler, E. and Strohmann, C. and Tacke, Reinhold and Schjelderup, L. and Aasen, A. and Lambrecht, G. and Christophe, J.}, title = {Stereoselective interaction of procyclidine, hexahydro-difenidol, hexbutinol and oxyphencyclimine, and of related antagonists, with four muscarinic receptors}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64237}, year = {1992}, abstract = {Wc invcstigatcd thc binding properlies of thc (R)- and (Sl-cnantiomcrs of thc muscarinic antagonists trihcxyphcnidyl, procyclidinc, hcxahydro-difcnidol. p-fluoro-hcxahydro-difcnidol. hcxbutinol, p-fluoro-hcxbutinnl. and thcir corrcsponding methiodidcs at muscarinic M\(_1\), M\(_2\)• M\(_3\) and M\(_4\) receptor subtypes. In addition. binding properlies of thc (R)- and (S)-cnantiomcrs of oxyphcncycliminc wcrc studicd. The {R)- cnantiomcrs (cutomcrs} of all the compounds had a grcatcr affinity than the (S)-isomcrs for thc four muscarinic rcccptor subtypcs. Thc binding pattcrns of thc (R)- and (S)-enantiomers wcrc gcncrally different. We did not obscrvc any gcncral corrclation hctwccn thc potcncy of thc high-affinity enantiomer and Lhc affinity ratio (cudismic ratio) of the two cnantiomcrs. Thc rcsuhs arc discusscd in tcrms of a 'four suhsitcs' binding modcl.}, subject = {Anorganische Chemie}, language = {en} } @article{WaelbroeckCamusTastenoyetal.1991, author = {Waelbroeck, M. and Camus, J. and Tastenoy, M. and Mutschler, E. and Strohmann, C. and Tacke, Reinhold and Lambrecht, G. and Christophe, J.}, title = {Binding affinities of hexahydro-difenidol and hexahydro-sila-difenidol analogues at four muscarinic receptor subtypes: constitutional and stereochemical aspects}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64128}, year = {1991}, abstract = {Hexahydro-sila-difenidoJ and eight analogues behaved as simple cumpetitive inhibitors of eHJN·methyl·scopoJamine binding to homogenates frorn human neuroblastoma NB-OK 1 cells (M\(_1\) sites), rat heart (M\(_2\) sites), rat pancreas (M\(_3\) sites), and rat striatum 'B' sites (M\(_4\) sites). Pyrrolidino- and hexamethyleneimino analogues showed the same sekctivity profile as the parent compound. Hexahydro-sila-difenidol methiodide and the methiodide of p-fluoro-hexahydro·sila-difenidol had a f{\"u}gher affinity but a lower selectivity than the tertiary amines. Compounds containing a p·methoxy, p-chJoro or p-fluoro substituent in the phenyl ring of hexahydro-sila-difenidol showed a qualitative)y similar selectivity profile as the parent compound (i.e., M\(_1\)= M\(_3\) = M\(_4\) >M\(_2\) ), but up to 16-fold lower affinities. o-Methoxy-hexahydro-sila-difenidol has a lower affinity than hexahydro-sila-difeni.:!o! at the four binding sites. lts selectivity profile (M\(_4\) > M\(_1\), M\(_3\) > M\(_2\) ) was different from hexahydro-sila-difenidol. Replacement of the centrat silicon atom of hexahydro-sila-difenidol, p-fluoro-hexahydro-sila-difenidol and thdr quatemary (N-methylated) analogues by a carbon atom did not change their binding affinities significantly. The iour muscarinic receptors showed a higher affinity for the (R)- than for the (S)-enantiomers of hexahydro-difenidol, p-fluorohexahydro-difenidol and their methiodides. The stereoselectivity varied depending on the receptor subtype and drug considered.}, subject = {Anorganische Chemie}, language = {en} } @article{WaelbroeckCamusTastenoyetal.1991, author = {Waelbroeck, M. and Camus, J. and Tastenoy, M. and Mutschler, E. and Strohmann, C. and Tacke, Reinhold and Lambrecht, G. and Christophe, J.}, title = {Stereoselectivity of (R)- and (S)-hexahydro-difenidol binding to neuroblastoma M\(_1\), cardiac M\(_2\), pancreatic M\(_3\), and striatum M\(_4\) muscarinic receptors}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64135}, year = {1991}, abstract = {(R)-Hexahydro-difenidol has a higher affinity for M\(_1\) receptors in NB-OK 1 cells, pancreas M\(_3\) and striatum M\(_4\) receptors (pKi 7.9 to 8.3) than for cardiac M2 receptors (pKi 7 .0). (8)-Hexahydro-difenidol, by contrast, is nonselective (pKi 5.8 to 6.1). Our goal in the present study was to evaluate the importance ofthe hydrophobic phenyl, and cyclohexyl rings of hexahydro-difenidol for the stereoselectivity and reeeptor selectivity of hexahydro-difenidol binding to the four muscarinic receptors. Our results indieated that replacement of the phenyl ring of hexahydro-difenidol by a cyclohexyl group <~ dicyclidol) and ofthe cyclohexyl ring by a phenyl moiety <~ difenidol) indueed a !arge (4- to 80-fold) decrease in binding affinity for all musearlnie receptors. Difenidol had a signifieant preference for M\(_1\) , M\(_3\) , and M\(_4\) over M\(_2\) receptors; dicyclidol, by eontrast, had a greater affinity for M\(_1\) and M\(_4\) than for M\(_2\) and M\(_3\) receptors. The binding free energy deerease due to replacement ofthe phenyl and the cyelohexyl groups of(R)-hexahydro-difenidol by, respectively, a eyclohexyl and a phenyl moiety was almostadditive in the ease of M\(_4\) (striatum) binding sites. In the ease ofthe cardiac M\(_2\), pancreatic M\(_3\) , or NB-OK 1 M\(_1\) receptors the respective binding free energies were not eompletely additive. These results suggest that the four (R)-hexahydro-difenidol ''binding moieties" (phenyl, cyclohexyl, hydroxy, and protonated amino group) cannot simultaneously form optimal interaetions with the M\(_1\), M\(_2\), and M\(_3\) muscarinic receptors. When eaeh of the hydrophobic groups is modified, the position of the whole molecule, relative to the four subsites, was changed to allow an optimal overall interaction with the musearlnie receptor.}, subject = {Anorganische Chemie}, language = {en} } @article{WaelbroeckCamusTastenoyetal.1990, author = {Waelbroeck, M. and Camus, J. and Tastenoy, M. and Lambrecht, G. and Mutschler, E. and Tacke, Reinhold and Christophe, J.}, title = {Stereoselectivity of procyclidine binding to muscarinic receptor subtypes M\(_1\), M\(_2\) and M\(_4\)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64034}, year = {1990}, abstract = {The goals of the present study were: (1) to investigate thc binding properlies oi (R)- and (S)-procyclidine and two aehiral derivatives of muscarinic M\(_1\)• M\(_2\) and M\(_4\) receptor subtypes and (2) to identify the interaetions which allow these receptors to diseriminate between the two stereoisomers. (R)-Procyclidine showed a higher affinity for human neuroblastoma NB-OK 1 muscarinie M\(_1\) and rat striatum musearinie M\(_4\) receptors. a~ compared to rat cardiac M\(_2\) receptors. (S)-Procyclidine had a 130-iold lower affinity than (R)-procyclidine for M\(_1\) and M\(_4\) receptors. and a 40-fold lower affinity for M\(_2\) receptors. Pyrrinol. the aehiral diphenyl derivative with the eyclohexyl g.roup of (S}-procyclidine replaeed by a phenyl group, has an eight-fold lower affinity for M\(_1\) and M\(_4\) receptors. as eompared to (R)-procyclidine, and a three-fold lower affinity for M\(_2\) receptors. Hexahydro-procyclidine. the eorresponding achiral dicyclohexyl compound, had a 10- to 20-fold lower affinity than (R)-procyclidine for the three reeeptors. The inerease in binding free energy, which is observed when the phenyl and eyclohexyl groups of procyelidine are separately replaeed by cyclohexyJ and phenyl groups, respectively. was additive in the ease of M\(_1\)• M\(_2\) and M\(_4\) receptcrs. This indicates that the musearinic reeeptor s!ereoseleetivity was based on the eoexistence of two binding sites, one preferring a phenylrather than eyclohexyl group and the seeond preferring a cyclohexyl rather than a phenyl group. In addition. there were aiso binding sites for the hydroxy moiety and the protonated amino group of the ligands. The greater affinity and stereoselectivity of M\(_1\) and M\(_4\) muscarinic receptors for (R)-procyelidine reflected the better fit of the eyclohexyl group of (R)-procyclidine to the subsite of M\(_1\) and M\(_4\) as compared to M\(_2\) receptors.}, subject = {Anorganische Chemie}, language = {en} } @article{WaelbroeckCamusTastenoyetal.1993, author = {Waelbroeck, M. and Camus, J. and Tastenoy, M. and Lambrecht, G. and Mutschler, E. and Kropfgans, M. and Sperlich, J. and Wiesenberger, F. and Tacke, R. and Christophe, J.}, title = {Thermodynamics of antagonist binding to rat muscarinic \(M_2\) receptors: antimuscarinics of the pridinol, sila-pridinol, diphenidol and sila-diphenidol type}, series = {British Journal of Pharmacology}, volume = {109}, journal = {British Journal of Pharmacology}, number = {2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128439}, pages = {360-370}, year = {1993}, abstract = {1 We studied the effect of temperature on the binding to rat heart \(M_2\) muscarinic receptors of antagonists related to the carbon/silicon pairs pridinol/sila-pridinol and diphenidol/sila-diphenidol (including three germanium compounds) and six structurally related pairs of enantiomers [(R)- and (S)-procyclidine, (R)- and (S)-trihexyphenidyl, (R)- and (S)-tricyclamol, (R)- and (S)-trihexyphenidyl methiodide, (R)- and (S)-hexahydro-diphenidol and (R)- and (S)-hexbutinol]. Binding affinities were determined in competition experiments using \([^3H]\)-N-methyl-scopolamine chloride as radioligand. The reference drugs were scopolamine and N-methyl-scopolamine bromide. 2 The affinity of the antagonists either increased or decreased with temperature, van 't Hoff plots were linear in the 278-310°K temperature range. Binding of all antagonists was entropy driven. Enthalpy changes varied from large negative values (down to \(-29 kJ mol^{-1}\)) to large positive values (up to \(+ 30 kJ mol^{-1}\)). 3 (R)-configurated drugs had a 10 to 100 fold greater affinity for \(M_2\) receptors than the corresponding (S)-enantiomers. Enthalpy and entropy changes of the respective enantiomers were different but no consistent pattern was observed. 4 When silanols \((R_3SiOH)\) were compared to carbinols \((R_3COH)\), the affinity increase caused by C/Si exchange varied between 3 and 10 fold for achiral drugs but was negligible in the case of chiral drugs. Silanols induced more favourable enthalpy and less favourable entropy changes than the corresponding carbinols when binding. Organogermanium compounds \((R_4Ge)\) when compared to their silicon counterparts (R4Si) showed no significant difference in affinity as well as in enthalpy and entropy changes. 5 Exchange of a cyclohexyl by a phenyl moiety was associated with an increase or a decrease in drug affinity (depending on the absolute configuration in the case of chiral drugs) and generally also with a more favourable enthalpy change and a less favourable entropy change of drug binding. 6 Replacement of a pyrrolidino by a piperidino group and increasing the length of the alkylene chain bridging the amino group and the central carbon or silicon atom were associated with either an increase or a decrease of entropy and enthalpy changes of drug binding. However, there was no clear correlation between these structural variations and the thermodynamic effects. 7 Taken together, these results suggest that hydrogen bond-forming OH groups and, to a lesser extent, polarizable phenyl groups contribute significantly to the thermodynamics of interactions between these classes of muscarinic antagonists and \(M_2\) muscarinic receptors.}, language = {en} } @article{WaelbroeckCamusTastenoyetal.1994, author = {Waelbroeck, M. and Camus, J. and Tastenoy, M. and Feifel, R. and Mutschler, E. and Tacke, R. and Strohmann, C. and Rafeiner, K. and Rodrigues de Miranda, J. F. and Lambrecht, G.}, title = {Binding and functional properties of hexocyclium and sila-hexocyclium derivatives to muscarinic receptor suhtypes}, series = {British Journal of Pharmacology}, volume = {112}, journal = {British Journal of Pharmacology}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-128265}, pages = {505-514}, year = {1994}, abstract = {1 We have compared the binding properties of several hexocyclium and sila-hexocyclium derivatives to muscarinic Ml receptors (in rat brain, human neuroblastoma (NB-OK I) cells and calf superior cervical ganglia), rat heart M2 receptors, rat pancreas M3 receptors and M4 receptors in rat striatum, with their functional antimuscarinic properties in rabbit vas deferens (Ml/M4-like), guinea-pig atria (M2), and guinea-pig ileum (M3) muscarinic receptors. 2 Si la-substitution (C/Si exchange) of hexocyclium (~ sila-hexocyclium) and demethyl-hexocyclium (~demethyl-sila-hexocyclium) did not significantly affect their affinities for muscarinic receptors. By contrast, sila-substitution of demethoxy-hexocyclium increased its affinity 2 to 3 fold for all the muscarinic receptor subtypes studied. 3 The p-fluoro- and p-chloro-derivatives of sila-hexocyclium had lower affinities than the parent compound at the four receptor subtypes, in binding and pharmacological studies. 4 In binding studies, o-methoxy-sila-hexocyclium (Ml = M4 ~ M3 ~ M2) had a much lower affinity than sila-hexocyclium for the four receptor subtypes, and discriminated the receptor subtypes more poorly than sila-hexocyclium (Ml = M3> M4> M2)' This is in marked contrast with the very clear selectivity of demethoxy-sila-hexocyclium for the prejunctional MtlM4-like heteroreceptors in rabbit vas deferens. 5 The tertiary amines demethyl-hexocyclium, demethyl-sila-hexocyclium and demethyl-o-methoxy-silahexocyclium had 10 to 30 fold lower affinities than the corresponding quaternary ammonium derivatives.}, language = {en} } @article{VerspohlTackeMutschleretal.1990, author = {Verspohl, E. J. and Tacke, Reinhold and Mutschler, E. and Lambrecht, G.}, title = {Muscarinic receptor subtypes in rat pancreatic islets: binding and functional studies}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-63993}, year = {1990}, abstract = {Cholinergie agents arepotent modulators of insulin release that aet via musearinie reeeptors. We now investigated the muscarinic receptor subtype present in rat panereatic islets in binding and funetional studies. Binding of 5 nM [ \(^3\)H]N-methylscopolamine ([\(^3\)H]NMS) was half maximal at 30 min. At 60 min, the maximal total bindingwas 1.29\% and the non-specifie binding (presence of 100 ,uM atropine) was 0.18\% of the total radioaetivity per 10 f.'g islet protein. Unlabelled atropine inhibited [\(^3\)H]NMS binding with an IC50 of ca. 30 nM. The rank order of antagonist high-affinity binding was atropine > sila-hexocyelium methyl sulfate (SiHC; M\(_1\) > M\(_3\) > M\(_2\) ) > pirenzepine (M\(_1\)> M\(_2\) = M\(_3\) ) = methoctramine (M\(_2\) > M\(_1\) > M\(_3\) ). The high-affinity K\(_d\)s were 8.5, 56, 1300 and 1300 nM, respectively. The high affinity Kd of the muscarinie receptor agonist, arecaidine propargyl ester (APE), was 8.1 nM. The EC\(_{50}\) for the biologieal effects of APE on insulin and glucagon secretion was 3.2 and 2.3 nM. The rank order for the high-affinity biological effects of antagonists (inhibition of APE-mediated insulin/ glucagon release) was almost the same as for binding. The data indicate that rat pancreatie islets contain neither an M\(_1\) subtype (high-affinity for pirenzepine) nor an M\(_2\) subtype (high-affinity for methoctramine) receptor. However, the data evidence an M\(_3\) receptor subtype, since SiHC in the absence of the M\(_1\) receptor subtype shows a relatively high affinity to the receptors in rat panereatic islets.}, subject = {Anorganische Chemie}, language = {en} } @article{TumirPavlovićSaftićCrnolatacetal.2023, author = {Tumir, Lidija-Marija and Pavlović Saftić, Dijana and Crnolatac, Ivo and Ban, Željka and Maslać, Matea and Griesbeck, Stefanie and Marder, Todd B. and Piantanida, Ivo}, title = {The nature of the (oligo/hetero)arene linker connecting two triarylborane cations controls fluorimetric and circular dichroism sensing of various ds-DNAs and ds-RNAs}, series = {Molecules}, volume = {28}, journal = {Molecules}, number = {11}, issn = {1420-3049}, doi = {10.3390/molecules28114348}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-319322}, year = {2023}, abstract = {A series of tetracationic bis-triarylborane dyes, differing in the aromatic linker connecting two dicationic triarylborane moieties, showed very high submicromolar affinities toward ds-DNA and ds-RNA. The linker strongly influenced the emissive properties of triarylborane cations and controlled the fluorimetric response of dyes. The fluorene-analog shows the most selective fluorescence response between AT-DNA, GC-DNA, and AU-RNA, the pyrene-analog's emission is non-selectively enhanced by all DNA/RNA, and the dithienyl-diketopyrrolopyrrole analog's emission is strongly quenched upon DNA/RNA binding. The emission properties of the biphenyl-analog were not applicable, but the compound showed specific induced circular dichroism (ICD) signals only for AT-sequence-containing ds-DNAs, whereas the pyrene-analog ICD signals were specific for AT-DNA with respect to GC-DNA, and also recognized AU-RNA by giving a different ICD pattern from that observed upon interaction with AT-DNA. The fluorene- and dithienyl-diketopyrrolopyrrole analogs were ICD-signal silent. Thus, fine-tuning of the aromatic linker properties connecting two triarylborane dications can be used for the dual sensing (fluorimetric and CD) of various ds-DNA/RNA secondary structures, depending on the steric properties of the DNA/RNA grooves.}, language = {en} } @article{TinajeroTrejoRanaNageletal.2016, author = {Tinajero-Trejo, Mariana and Rana, Namrata and Nagel, Christoph and Jesse, Helen E. and Smith, Thomas W. and Wareham, Lauren K. and Hippler, Michael and Schatzschneider, Ulrich and Poole, Robert K.}, title = {Antimicrobial Activity of the Manganese Photoactivated Carbon Monoxide-Releasing Molecule [Mn(CO)\(_3\)(tpa-kappa\(^3\)N)]\(^+\) Against a Pathogenic Escherichia coli that Causes Urinary Infections}, series = {Antioxidants \& Redox Signaling}, volume = {24}, journal = {Antioxidants \& Redox Signaling}, number = {14}, doi = {10.1089/ars.2015.6484}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188910}, pages = {765-780}, year = {2016}, abstract = {Aims: We set out to investigate the antibacterial activity of a new Mn-based photoactivated carbon monoxide-releasing molecule (PhotoCORM, [Mn(CO)\(_3\)(tpa-kappa\(^3\)N)]\(^+\)) against an antibiotic-resistant uropathogenic strain (EC958) of Escherichia coli. Results: Activated PhotoCORM inhibits growth and decreases viability of E. coli EC958, but non-illuminated carbon monoxide-releasing molecule (CORM) is without effect. NADH-supported respiration rates are significantly decreased by activated PhotoCORM, mimicking the effect of dissolved CO gas. CO from the PhotoCORM binds to intracellular targets, namely respiratory oxidases in strain EC958 and a bacterial globin heterologously expressed in strain K-12. However, unlike previously characterized CORMs, the PhotoCORM is not significantly accumulated in cells, as deduced from the cellular manganese content. Activated PhotoCORM reacts avidly with hydrogen peroxide producing hydroxyl radicals; the observed peroxide-enhanced toxicity of the PhotoCORM is ameliorated by thiourea. The PhotoCORM also potentiates the effect of the antibiotic, doxycycline. Innovation: The present work investigates for the first time the antimicrobial activity of a light-activated PhotoCORM against an antibiotic-resistant pathogen. A comprehensive study of the effects of the PhotoCORM and its derivative molecules upon illumination is performed and mechanisms of toxicity of the activated PhotoCORM are investigated. Conclusion: The PhotoCORM allows a site-specific and time-controlled release of CO in bacterial cultures and has the potential to provide much needed information on the generality of CORM activities in biology. Understanding the mechanism(s) of activated PhotoCORM toxicity will be key in exploring the potential of this and similar compounds as antimicrobial agents, perhaps in combinatorial therapies with other agents.}, language = {en} } @phdthesis{Tian2021, author = {Tian, Yaming}, title = {Selective C-X and C-H Borylation by N-Heterocyclic Carbene Nickel(0) Complex}, doi = {10.25972/OPUS-21300}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-213004}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2021}, abstract = {Organoboron compounds are important building blocks in organic synthesis, materials science, and drug discovery. The development of practical and convenient ways to synthesize boronate esters attracted significant interest. Photoinduced borylations originated with stoichiometric reactions of arenes and alkanes with well-defined metal-boryl complexes. Now photoredox-initiated borylations, catalyzed either by transition-metal or organic photocatalysts, and photochemical borylations with high efficiency have become a burgeoning area of research. In this chapter, we summarize research in the field of photocatalytic C-X borylation, especially emphasizing recent developments and trends, based on transition-metal catalysis, metal-free organocatalysis and direct photochemical activation. We focus on reaction mechanisms involving single electron transfer (SET), triplet energy transfer (TET), and other radical processes. We developed a highly selective photocatalytic C-F borylation method that employs a rhodium biphenyl complex as a triplet sensitizer and the nickel catalyst [Ni(IMes)2] (IMes = 1,3-dimesitylimidazolin-2-ylidene) for the C-F bond activation and defluoroborylation process. This tandem catalyst system operates with visible (400 nm) light and achieves borylation of a wide range of fluoroarenes with B2pin2 at room temperature in excellent yields and with high selectivity. Direct irradiation of the intermediary C-F bond oxidative addition product trans-[NiF(ArF)(IMes)2] leads to fast decomposition when B2pin2 is present. This destructive pathway can be bypassed by indirect excitation of the triplet states of the nickel(II) complex via the photoexcited rhodium biphenyl complex. Mechanistic studies suggest that the exceptionally long-lived triplet excited state of the Rh biphenyl complex used as the photosensitizer allows for efficient triplet energy transfer to trans-[NiF(ArF)(IMes)2], which leads to dissociation of one of the NHC ligands. This contrasts with the majority of current photocatalytic transformations, which employ transition metals as excited state single electron transfer agents. We have previously reported that C(arene)-F bond activation with [Ni(IMes)2] is facile at room temperature, but that the transmetalation step with B2pin2 is associated with a high energy barrier. Thus, this triplet energy transfer ultimately leads to a greatly enhanced rate constant for the transmetalation step and thus for the whole borylation process. While addition of a fluoride source such as CsF enhances the yield, it is not absolutely required. We attribute this yield-enhancing effect to (i) formation of an anionic adduct of B2pin2, i.e. FB2pin2-, as an efficient, much more nucleophilic {Bpin-} transfer reagent for the borylation/transmetalation process, and/or (ii) trapping of the Lewis acidic side product FBpin by formation of [F2Bpin]- to avoid the formation of a significant amount of NHC-FBpin and consequently of decomposition of {Ni(NHC)2} species in the reaction mixture. We reported a highly selective and general photo-induced C-Cl borylation protocol that employs [Ni(IMes)2] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the radical borylation of chloroarenes. This photo-induced system operates with visible light (400 nm) and achieves borylation of a wide range of chloroarenes with B2pin2 at room temperature in excellent yields and with high selectivity, thereby demonstrating its broad utility and functional group tolerance. Mechanistic investigations suggest that the borylation reactions proceed via a radical process. EPR studies demonstrate that [Ni(IMes)2] undergoes very fast chlorine atom abstraction from aryl chlorides to give [NiI(IMes)2Cl] and aryl radicals. Control experiments indicate that light promotes the reaction of [NiI(IMes)2Cl] with aryl chlorides generating additional aryl radicals and [NiII(IMes)2Cl2]. The aryl radicals react with an anionic sp2-sp3 diborane [B2pin2(OMe)]- formed from B2pin2 and KOMe to yield the corresponding borylation product and the [Bpin(OMe)]•- radical anion, which reduces [NiII(IMes)2Cl2] under irradiation to regenerate [NiI(IMes)2Cl] and [Ni(IMes)2] for the next catalytic cycle. A highly efficient and general protocol for traceless, directed C3-selective C-H borylation of indoles with [Ni(IMes)2] as the catalyst was achieved. Activation and borylation of N-H bonds by [Ni(IMes)2] is essential to install a Bpin moiety at the N-position as a traceless directing group, which enables the C3-selective borylation of C-H bonds. The N-Bpin group which is formed is easily converted in situ back to an N-H group by the oxidiative addition product of [Ni(IMes)2] and in situ-generated HBpin. The catalytic reactions are operationally simple, allowing borylation of of a variety of substituted indoles with B2pin2 in excellent yields and with high selectivity. The C-H borylation can be followed by Suzuki-Miyaura cross-coupling of the C-borylated indoles in an overall two-step, one-pot process providing an efficient method for synthesizing C3-functionalized heteroarenes.}, subject = {Borylierung}, language = {en} } @article{ThiessMellerupBraunschweig2019, author = {Thiess, Torsten and Mellerup, Soren K. and Braunschweig, Holger}, title = {B-B Cleavage and Ring-Expansion of a 1,4,2,3-Diazadiborinine with N-Heterocyclic Carbenes}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {59}, doi = {10.1002/chem.201903259}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206173}, pages = {13572-13578}, year = {2019}, abstract = {A 1,4,2,3-diazadiborinine derivative was found to form Lewis adducts with strong two-electron donors such as N-heterocyclic and cyclic (alkyl)(amino)carbenes. Depending on the donor, some of these Lewis pairs are thermally unstable, converting to sole B,N-embedded products upon gentle heating. The products of these reactions, which have been fully characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction, were identified as B,N-heterocycles with fused 1,5,2,4-diazadiborepine and 1,4,2-diazaborinine rings. Computational modelling of the reaction mechanism provides insight into the formation of these unique structures, suggesting that a series of B-H, C-N, and B-B bond activation steps are responsible for these "intercalation" reactions between the 1,4,2,3-diazadiborinine and NHCs.}, language = {en} } @article{ThiessErnstKupferetal.2020, author = {Thiess, Torsten and Ernst, Moritz and Kupfer, Thomas and Braunschweig, Holger}, title = {Facile Access to Substituted 1,4-Diaza-2,3-Diborinines}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {13}, doi = {10.1002/chem.201905356}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-214650}, pages = {2967 -- 2972}, year = {2020}, abstract = {Several bis(dimethylamino)-substituted 1,4-diaza-2,3-diborinines (DADBs) were synthesized with variable substituents at the backbone nitrogen atoms. By reaction with HCl or BX\(_{3}\) (X=Br, I), these species were successfully converted into their synthetically more useful halide congeners. The high versatility of the generated B-X bonds in further functionalization reactions at the boron centers was demonstrated by means of salt elimination (MeLi) and commutation (NMe\(_{2}\) DADBs) reactions, thus making the DADB system a general structural motif in diborane(4) chemistry. A total of 18 DADB derivatives were characterized in the solid state by X-ray diffraction, revealing a strong dependence of the heterocyclic bonding parameters from the exocyclic substitution pattern at boron. According to our experiments towards the realization of a Dipp-substituted, sterically encumbered DADB, the mechanism of DADB formation proceeds via a transient four-membered azadiboretidine intermediate that subsequently undergoes ring expansion to afford the six-membered DADB heterocycle.}, language = {en} } @article{TenderaSchaubKrahfussetal.2020, author = {Tendera, Lukas and Schaub, Thomas and Krahfuss, Mirjam J. and Kuntze-Fechner, Maximilian W. and Radius, Udo}, title = {Large vs. Small NHC Ligands in Nickel(0) Complexes: The Coordination of Olefins, Ketones and Aldehydes at [Ni(NHC)\(_{2}\)]}, series = {European Journal of Inorganic Chemistry}, volume = {2020}, journal = {European Journal of Inorganic Chemistry}, number = {33}, doi = {10.1002/ejic.202000493}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-216058}, pages = {3194 -- 3207}, year = {2020}, abstract = {Investigations concerning the reactivity of Ni(0) complexes [Ni(NHC)\(_{2}\)] of NHCs (N-heterocyclic carbene) of different steric demand, Mes\(_{2}\)Im (= 1,3-dimesitylimidazoline-2-ylidene) and iPr\(_{2}\)Im (= 1,3-diisopropyl-imidazoline-2-ylidene), with olefins, ketones and aldehydes are reported. The reaction of [Ni(Mes\(_{2}\)Im)\(_{2}\)] 1 with ethylene or methyl acrylate afforded the complexes [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-C\(_{2}\)H\(_{4}\))] 3 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-(C,C)-H\(_{2}\)C=CHCOOMe)] 4, as it was previously reported for [Ni\(_{2}\)(iPr\(_{2}\)Im)\(_{4}\)(µ-(η\(^{2}\):η\(^{2}\))-COD)] 2 as a source for [Ni(iPr\(_{2}\)Im)\(_{2}\)]. In contrast to 2, complex 1 does not react with sterically more demanding olefins such as tetramethylethylene, 1,1-diphenylethylene and cyclohexene. The reaction of [Ni(NHC)\(_{2}\)] with more π-acidic ketones or aldehydes led to formation of complexes with side-on η\(^{2}\)-(C,O)-coordinating ligands: [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH\(^{t}\)Bu)] 5, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CHPh)] 6, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CMePh)] 7, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CPh\(_{2}\))] 8, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(4-F-C\(_{6}\)H\(_{4}\))\(_{2}\))] 9, [Ni(iPr\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(OMe)(CF\(_{3}\)))] 10 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CHPh)] 11, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(CH(CH\(_{3}\))\(_{2}\)))] 12, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(4-NMe\(_{2}\)-C\(_{6}\)H\(_{4}\)))] 13, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CH(4-OMe-C\(_{6}\)H\(_{4}\)))] 14, [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=CPh\(_{2}\))] 15 and [Ni(Mes\(_{2}\)Im)\(_{2}\)(η\(^{2}\)-O=C(4-F-C\(_{6}\)H\(_{4}\))\(_{2}\))] 16. The reaction of 1 and 2 with these simple aldehydes and ketones does not lead to a significantly different outcome, but NHC ligand rotation is hindered for the Mes\(_{2}\)Im complexes 3, 4 and 11-16 according to NMR spectroscopy. The solid-state structures of 3, 4, 11 and 12 reveal significantly larger C\(_{NHC}\)-Ni-C\(_{NHC}\) angles in the Mes\(_{2}\)Im complexes compared to the iPr\(_{2}\)Im complexes. As electron transfer in d\(^{8}\)- (or d\(^{10}\)-) ML\(_{2}\) complexes to π-acidic ligands depends on the L-M-L bite angle, the different NHCs lead thus to a different degree of electron transfer and activation of the olefin, aldehyde or ketone ligand, i.e., [Ni(iPr\(_{2}\)Im)\(_{2}\)] is the better donor to these π-acidic ligands. Furthermore, we identified two different side products from the reaction of 1 with benzaldehyde, trans-[Ni(Mes\(_{2}\)Im)\(_{2}\)H(OOCPh)] 17 and [Ni\(_{2}\)(Mes\(_{2}\)Im)\(_{2}\)(µ\(_{2}\)-CO)(µ\(_{2}\)-η\(^{2}\)-C,O-PhCOCOPh)] 18, which indicate that radical intermediates and electron transfer processes might be of importance in the reaction of 1 with aldehydes and ketones.}, language = {en} } @article{TenderaLuffKrummenacheretal.2022, author = {Tendera, Lukas and Luff, Martin S. and Krummenacher, Ivo and Radius, Udo}, title = {Cationic Nickel d\(^{9}\)-Metalloradicals [Ni(NHC)\(_{2}\)]\(^{+}\)}, series = {European Journal of Inorganic Chemistry}, volume = {2022}, journal = {European Journal of Inorganic Chemistry}, number = {31}, doi = {10.1002/ejic.202200416}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293702}, year = {2022}, abstract = {A series of five new homoleptic, linear nickel d\(^{9}\)-complexes of the type [Ni\(^{I}\)(NHC)\(_{2}\)]\(^{+}\) is reported. Starting from the literature known Ni(0) complexes [Ni(Mes\(_{2}\)Im)\(_{2}\)] 1, [Ni(Mes\(_{2}\)Im\(^{H2}\))2] 2, [Ni(Dipp\(_{2}\)Im)\(_{2}\)] 3, [Ni(Dipp\(_{2}\)Im\(^{H2}\))\(_{2}\)] 4 and [Ni(cAAC\(^{Me}\))\(_{2}\)] 5 (Mes\(_{2}\)Im=1,3-bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene, Mes\(_{2}\)Im\(^{H2}\)=1,3-bis(2,4,6-trimethylphenyl)-imidazolidin-2-ylidene, Dipp\(_{2}\)Im=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene, Dipp\(_{2}\)Im\(^{H2}\)=1,3-bis(2,6-diisopropylphenyl)-imidazolidin-2-ylidene, cAAC\(^{Me}\)=1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-yliden), their oxidized Ni(I) analogues [Ni\(^{I}\)(Mes\(_{2}\)Im)\(_{2}\)][BPh\(_{4}\)] 1\(^{+}\), [Ni\(^{I}\)(Mes\(_{2}\)Im\(^{H2}\))\(_{2}\)][BPh\(_{4}\)] 2\(^{+}\), [Ni\(^{I}\)(Dipp\(_{2}\)Im)\(_{2}\)][BPh\(_{4}\)] 3\(^{+}\), [Ni\(^{I}\)(Dipp\(_{2}\)Im\(^{H2}\))\(_{2}\)][BPh\(_{4}\)] 4\(^{+}\) and [Ni\(^{I}\)(cAAC\(^{Me}\))\(_{2}\)][BPh\(_{4}\)] 5\(^{+}\) were synthesized by one-electron oxidation with ferrocenium tetraphenyl-borate. The complexes 1\(^{+}\)-5\(^{+}\) were fully characterized including X-ray structure analysis. The complex cations reveal linear geometries in the solid state and NMR spectra with extremely broad, paramagnetically shifted resonances. DFT calculations predicted an orbitally degenerate ground state leading to large magnetic anisotropy, which was verified by EPR measurements in solution and on solid samples. The magnetic anisotropy of the complexes is highly dependent from the steric protection of the metal atom, which results in a noticeable decrease of the g-tensor anisotropy for the N-Mes substituted complexes 1\(^{+}\) and 2\(^{+}\) in solution due to the formation of T-shaped THF adducts.}, language = {en} } @article{TenderaHelmKrahfussetal.2021, author = {Tendera, Lukas and Helm, Moritz and Krahfuss, Mirjam and Kuntze-Fechner, Maximilian W. and Radius, Udo}, title = {Case Study of N-\(^{i}\)Pr versus N-Mes Substituted NHC Ligands in Nickel Chemistry: The Coordination and Cyclotrimerization of Alkynes at [Ni(NHC)\(_{2}\)]}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {71}, doi = {10.1002/chem.202103093}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257137}, pages = {17849-17861}, year = {2021}, abstract = {A case study on the effect of the employment of two different NHC ligands in complexes [Ni(NHC)\(_{2}\)] (NHC=\(^{i}\)Pr\(_{2}\)Im\(^{Me}\) 1\(^{Me}\), Mes\(_{2}\)Im 2) and their behavior towards alkynes is reported. The reaction of a mixture of [Ni\(_{2}\)(\(^{i}\)Pr\(_{2}\)Im\(^{Me}\))\(_{4}\)(μ-(η\(^{2}\) : η\(^{2}\))-COD)] B/ [Ni(\(^{i}\)Pr\(_{2}\)Im\(^{Me}\))\(_{2}\)(η\(^{4}\)-COD)] B' or [Ni(Mes\(_{2}\)Im)\(_{2}\)] 2, respectively, with alkynes afforded complexes [Ni(NHC)\(_{2}\)(η\(^{2}\)-alkyne)] (NHC=\(^{i}\)Pr\(_{2}\)Im\(^{Me}\): alkyne=MeC≡CMe 3, H\(_{7}\)C\(_{3}\)C≡CC\(_{3}\)H\(_{7}\) 4, PhC≡CPh 5, MeOOCC≡CCOOMe 6, Me\(_{3}\)SiC≡CSiMe\(_{3}\) 7, PhC≡CMe 8, HC≡CC\(_{3}\)H\(_{7}\) 9, HC≡CPh 10, HC≡C(p-Tol) 11, HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)) 12, HC≡CCOOMe 13; NHC=Mes\(_{2}\)Im: alkyne=MeC≡CMe 14, MeOOCC≡CCOOMe 15, PhC≡CMe 16, HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)) 17, HC≡CCOOMe 18). Unusual rearrangement products 11 a and 12 a were identified for the complexes of the terminal alkynes HC≡C(p-Tol) and HC≡C(4-\(^{t}\)Bu-C\(_{6}\)H\(_{4}\)), 11 and 12, which were formed by addition of a C-H bond of one of the NHC N-\(^{i}\)Pr methyl groups to the C≡C triple bond of the coordinated alkyne. Complex 2 catalyzes the cyclotrimerization of 2-butyne, 4-octyne, diphenylacetylene, dimethyl acetylendicarboxylate, 1-pentyne, phenylacetylene and methyl propiolate at ambient conditions, whereas 1\(^{Me}\) is not a good catalyst. The reaction of 2 with 2-butyne was monitored in some detail, which led to a mechanistic proposal for the cyclotrimerization at [Ni(NHC)\(_{2}\)]. DFT calculations reveal that the differences between 1\(^{Me}\) and 2 for alkyne cyclotrimerization lie in the energy profile of the initiation steps, which is very shallow for 2, and each step is associated with only a moderate energy change. The higher stability of 3 compared to 14 is attributed to a better electron transfer from the NHC to the metal to the alkyne ligand for the N-alkyl substituted NHC, to enhanced Ni-alkyne backbonding due to a smaller C\(_{NHC}\)-Ni-C\(_{NHC}\) bite angle, and to less steric repulsion of the smaller NHC \(^{i}\)Pr\(_{2}\)Im\(^{Me}\).}, language = {en} } @phdthesis{Tendera2023, author = {Tendera, Lukas}, title = {NHC-ligated Nickel(0)-Complexes: Bond Activation, Redox Behavior and Catalysis}, doi = {10.25972/OPUS-29065}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-290654}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {This thesis describes the synthesis and reactivity of bis-NHC ligated nickel(0)-complexes and their application in catalytic cyclization and borylation reactions of alkynes. The focus of the presented work lies on the investigation of the electronic and steric impact of different NHC ligands on the reactivity and catalytic activity of [Ni(NHC)2] complexes. Since d10 ML2 complexes play a decisive role for numerous catalytic reactions, such as the Suzuki-Miyaura cross-coupling, the first chapter provides an overview about the general properties of NHCs and the chemistry of NHC-ligated nickel complexes, their synthesis, characterization, reactivity, and application in catalysis.}, subject = {{\"U}bergangsmetallkomplexe}, language = {en} } @article{TaniniPecchiIgnat’evetal.2022, author = {Tanini, Damiano and Pecchi, Tommaso and Ignat'ev, Nikolai V. and Capperucci, Antonella}, title = {Ionic liquids-assisted ring opening of three-membered heterocycles with thio- and seleno-silanes}, series = {Catalysts}, volume = {12}, journal = {Catalysts}, number = {10}, issn = {2073-4344}, doi = {10.3390/catal12101259}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-290350}, year = {2022}, abstract = {Ring opening reactions of strained heterocycles (epoxides, aziridines, thiiranes) by silyl chalcogenides, such as thiosilanes and selenosilanes, can be efficiently performed in a variety of ionic liquids, which can behave as reaction media and in some cases also as catalysts. This protocol enables an alternative access to β-functionalized sulfides and selenides under mild conditions.}, language = {en} } @article{TackeWuttkeHenke1992, author = {Tacke, Reinhold and Wuttke, F. and Henke, H.}, title = {Zur Stereochemie der mikrobiellen Reduktion von rac-Acetyl( t-butyl)methylphenylsilan mit Trigonopsis variabilis (DSM 70714) und Corynebacterium dioxydans (ATCC 21766): Aufkl{\"a}rung der absoluten Konfiguration der Biotransformationsprodukte (SiR,CR)- und ( SiS ,CR)-t-Butyl( 1-hydroxyethyl)methylphenylsilan}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64176}, year = {1992}, abstract = {No abstract available}, subject = {Anorganische Chemie}, language = {en} } @article{TackeWagnerBrakmannetal.1993, author = {Tacke, Reinhold and Wagner, S. A. and Brakmann, S. and Wuttke, F. and Eilert, U. and Fischer, L. and Syldatk, C.}, title = {Synthesis of acetyldimethyl(phenyl)silane and its enantioselective conversion into (R)-(1-hydroxyethyl)dimethyl(phenyl)silane by plant cell suspension culytures of Symphytum officinale L. and Ruta graveolens L.}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64299}, year = {1993}, abstract = {Starting from chlorodimethyl(phenyl)silane (3), acetyldimethyl(phenyl)silane (l) was prepared by a two-step synthesis in a total yield of 90\% [PhMe\(_2\)SiCl (3)-> PhMe\(_2\)SiCCOMe)=CH\(_2\) (4)-> PhMe\(_2\)SiC(O)Me (1)]. The prochiral acetylsilane 1 was transfonned enantioselectively into (R)-(1-hydroxyethyl)dimethyl(phenyl)silane [(R)-2] using plant cell Suspension cultures of Symphytum officinale L. or Ruta graveolens L. Under preparative conditions (300-mg scale, not optimized), (R)-2 was isolated in 15\% (Symphytum) and 9\% yield (Ruta), respectively. The enantiomeric purities of the products were 81\% ee (Syrnphytum) and 60\% ee (Ruta), respectively.}, subject = {Anorganische Chemie}, language = {en} } @article{TackeStrohmannSargeetal.1989, author = {Tacke, Reinhold and Strohmann, C. and Sarge, S. and Cammenga, H. K. and Schomburg, D. and Mutschler, E. and Lambrecht, G.}, title = {Darstellung und Eigenschaften der Enantiomere des selektiven Antimuscarinikums 1-Cyclohexyl-1-phenyl-4-piperidino-1-butanol (Hexahydro-Difenidol)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-63950}, year = {1989}, abstract = {No abstract available}, subject = {Anorganische Chemie}, language = {en} } @article{TackeSperlichBecker1994, author = {Tacke, Reinhold and Sperlich, J. and Becker, B.}, title = {Bis[2,3-naphthalenediolato(2-)](pyrrolidinio-methyl)germanate-tetartoacetonitrile, the first zwitterionic \(\lambda_5\)-germanate: synthesis and crystal structure analysis}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64329}, year = {1994}, abstract = {The zwitterionic spirocyclic \(\lambda_5\)-germanate bis(2,3-naphthalenediolato( 2-)](pyrrolidiniomethyl)germanate (8) was synthesized and the crystal structure of its tetartoacetonitrile solvate 8 · 1/4 CH\(_3\)CN studied by single-crystal X-ray diffraction. Compound 8 was prepared by reaction of (MeO)\(_3\)GeCH\(_2\)NC\(_4\)H\(_8\) (11; NC\(_4\)H\(_8\) = pyrrolidino) with two equivalents of 2,3-naphthalenediol (isolated as 8 · 1/4 CH\(_3\)CN; yield 92\%). The coordination polyhedron around the pentacoordi- naphthalenediolatonate germanium atom of 8 · 1/4 CH\(_3\)CN can be described as a strongly distorted trigonal bipyramid (the structure is displaced by 38.9\% from the ideal trigonal bipyrarnid towards the ideal square pyramid), the carbon atom occupying an equatorial position. In the crystal lattice of 8 · 1/4 CH\(_3\)CN, the zwitterions form intermolecular N-H ... o hydrogen bonds leading to the formation of dimers. 1H- and \(^{13}\C-NMR studies revealed that 8 also exists in solution ([D\(_6\)]DMSO).}, subject = {Anorganische Chemie}, language = {en} } @article{TackeSaad1977, author = {Tacke, Reinhold and Saad, S. M.}, title = {Silylation of cellulose}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-78368}, year = {1977}, abstract = {Ethane-l:2-diol and propane-l:3-diol reaet with 1: 1:3:3-tetramethyl-l:3-dichlorodisiloxane forming the corresponding rings. However, no ring compounds could be traced tbrough the reaction between butane-l :4-diol, glycerol and the dichlorodisiloxane respectively, where only polymeric compounds are formed. The silylation products of the di- and trihydroxy alcohols, as model compounds, has confirmed that the ring formation during silylation of cellulose with dichlorodisiloxane is uncertain.}, subject = {Anorganische Chemie}, language = {en} } @article{TackeRafeinerStrohmannetal.1989, author = {Tacke, Reinhold and Rafeiner, K. and Strohmann, C. and Mutschler, E. and Lambrecht, G.}, title = {Synthesis of the selective antimuscarinic agent 4-{[cyclohexylhydroxy(2-methoxyphenyl)silyl]methyl}-1,1-dimethylpiperazinium methyl sulfate (o-methoxy-sila-hexocyclium methyl sulfate)}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-63930}, year = {1989}, abstract = {The synthesis of the potent and highly selective silicon-containing antimuscarinic agent o-methoxysila- hexocyclium methyl sulfate and its corresponding tertiary amine (isolated as the dihydrochloride) is described. The quarternary compound is an omethoxy derivative of sila-hexocyclium methyl sulfate, which represents one of the tools currently used in experimental pharmacology for the subclassification of muscarinic receptors. The omethoxy derivative, the pharmacological profile of which differs substantially from tbat of the nonmethoxy compound, is also recommended as a tool for the investigation of muscarinic receptor heterogeneity.}, subject = {Anorganische Chemie}, language = {en} } @article{TackePikiesWiesenbergeretal.1994, author = {Tacke, Reinhold and Pikies, J. and Wiesenberger, F. and Ernst, L. and Schomburg, D. and Waelbroeck, M. and Christophe, J. and Lambrecht, G. and Gross, J. and Mutschler, E.}, title = {Sila-biperiden und endo-Sila-biperiden: Synthesen, Kristallstrukturen und antimuscarinische Eigenschaften}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64303}, year = {1994}, abstract = {Starting from trichloro(vinyl)silane (Cl\(_3\)SiCH=CH\(_2\)), the musearinic antagonists sila-biperiden [rac-(SiRS,C2SR>-ao-2] and endosila- biperiden [rac-(SiRS,C2SR)-endo-2] were prepared by a seven-step synthesis. Both silanols are configurationally stableininert organic solvents but undergo slow epimerization in aqueous solution (pH 7.4, 32°C) by inversion of the configuration at the silicon atom. The relative configurations of sila-biperiden and endo-sila-biperiden were detennined by single-crystal X-ray diffraction. Both compounds form intennolecular 0-H · · · N hydrogen bonds in the crystal leading to the fonnation of centrosymmetric dimers (sila-biperiden) and infinite chains (endo-sila-biperiden), respectively. Sila-biperiden is a silicon analogue (C/Si exchange) of the antiparkinsonian drug biperiden [rac-(CRS/C2SR}-exo-1]. In functional phannacological experiments, as well as in radioligand competition studies, biperiden, sila-biperiden and endo-sila-biperiden behaved as simple competitive antagonists at muscarinic Ml-, M2-, M3- and M4-receptors. The three compounds displayed the highest affinity for Ml-receptors (pA\(_2\) values: 8.72-8.80; pK\(_i\) values: 8.8-9.1), intermediate affinity for M4- and M3-receptors, and lowest affinity for M2-receptors (pA\(_2\) values: 7.57-7.79; pK\(_i\) values: 7.7-7.8). The affinity profile (Ml >. M4 > M3 > M2) of biperiden, sila-biperiden and endo-sila-biperiden is qualitatively similar to that of the M1-selective muscarinic antagonist pirenzepine. The antimuscarinic properlies of the C/Si analogues biperiden and sila-biperiden are almost identical.}, subject = {Anorganische Chemie}, language = {en} } @article{TackeMuehleisenJones1994, author = {Tacke, Reinhold and M{\"u}hleisen, M. and Jones, P. G.}, title = {The first zwitterionic, optically active disilicate with pentacoordinate silicon}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64358}, year = {1994}, abstract = {No abstract available}, subject = {Anorganische Chemie}, language = {en} } @article{TackeMuehleisen1994, author = {Tacke, Reinhold and M{\"u}hleisen, M.}, title = {Bis[benzilato(2-)-O\(^1\),O\(^2\)][2-(dimethylammonio)ethoxy]silicate: synthesis and structural characterization of a zwitterionic \(\lambda^5\)Si-silicate with a SiO\(_5\) framework}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64400}, year = {1994}, abstract = {No abstract available}, subject = {Anorganische Chemie}, language = {en} }