@phdthesis{Arnold2013, author = {Arnold, Thomas}, title = {Reaktivit{\"a}t von Disilamolybd{\"a}nocenophanen}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-83865}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2013}, abstract = {Es wird die Reaktivit{\"a}t eines hochgespannten und reaktiven [1],[1]-Disilamolybd{\"a}nocenophanes gegen{\"u}ber unges{\"a}ttigten Substraten, E-H Funktionen und E-E-Bindungen untersucht. Die Produkte wurden mittels spektroskopischer Methoden in L{\"o}sung sowie im Festk{\"o}rper identifiziert und charakterisiert. Weiterhin wird die Reaktivit{\"a}t eines [2]-Disilamolybd{\"a}nocenophanes ebenfalls gegen{\"u}ber unges{\"a}ttigten Substraten und E-E-Bindungen sowie gegen{\"u}ber Pt(0)-Verbindungen erforscht. Die erhaltenen Komplexe wurden sowohl im Festk{\"o}rper, als auch in L{\"o}sung spektroskopisch untersucht und charakterisiert.}, subject = {Metallocene}, language = {de} } @phdthesis{Bissinger2013, author = {Bissinger, Philipp}, title = {Synthese, Struktur und Reaktivit{\"a}t Basen-stabilisierter Borane und Diborene}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-79144}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2013}, abstract = {Umsetzungen N-heterocyclischer Carbene mit Boranen f{\"u}hren zur Bildung von „Lewis-S{\"a}ure-Base-Addukten". In Abh{\"a}ngigkeit des Substitutionsmusters der eingesetzten Borane bzw. Carbene eignen sich die erhaltenen Addukte als Ausgangsverbindungen zur Realisierung verschiedener Strukturmotive. Mit geeigneten {\"U}bergangsmetallfragmenten gelingt die Darstellung von sigma-Boran-Komplexen bzw. Basen-stabilisierter Boryl-Komplexe, welche mittels spektroskopischer Methoden sowohl im Festk{\"o}rper, als auch in L{\"o}sung untersucht wurden. Ebenfalls gelingt die Synthese Basen-stabilisierter Borirane und einer tetraedrischen Borid-Spezies. Zudem wird ein selektiver Zugang zu Basen-stabilisierten Diborenen entwickelt, wobei deren Bindungssituation und Reaktivit{\"a}t im Detail diskutiert wird. So kann das B=B-Fragment in polymere Spezies eingebunden werden oder als Ligand an {\"U}bergangsmetalle koordinieren.}, subject = {Borane}, language = {de} } @article{BruecknerFantuzziStennettetal.2021, author = {Br{\"u}ckner, Tobias and Fantuzzi, Felipe and Stennett, Tom E. and Krummenacher, Ivo and Dewhurst, Rian D. and Engels, Bernd and Braunschweig, Holger}, title = {Isolation of neutral, mono-, and dicationic B\(_2\)P\(_2\) rings by diphosphorus addition to a boron-boron triple bond}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {24}, doi = {10.1002/anie.202102218}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256451}, pages = {13661-13665}, year = {2021}, abstract = {The NHC-stabilised diboryne (B\(_2\)(SIDep)\(_2\); SIDep=1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene) undergoes a high-yielding P-P bond activation with tetraethyldiphosphine at room temperature to form a B\(_2\)P\(_2\) heterocycle via a diphosphoryldiborene by 1,2-diphosphination. The heterocycle can be oxidised to a radical cation and a dication, respectively, depending on the oxidant used and its counterion. Starting from the planar, neutral 1,3-bis(alkylidene)-1,3-diborata-2,4-diphosphoniocyclobutane, each oxidation step leads to decreased B-B distances and loss of planarity by cationisation. X-ray analyses in conjunction with DFT and CASSCF/NEVPT2 calculations reveal closed-shell singlet, butterfly-shaped structures for the NHC-stabilised dicationic B\(_2\)P\(_2\) rings, with their diradicaloid, planar-ring isomers lying close in energy.}, language = {en} } @article{CzernetzkiArrowsmithFantuzzietal.2021, author = {Czernetzki, Corinna and Arrowsmith, Merle and Fantuzzi, Felipe and G{\"a}rtner, Annalena and Tr{\"o}ster, Tobias and Krummenacher, Ivo and Schorr, Fabian and Braunschweig, Holger}, title = {A neutral beryllium(I) radical}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {38}, doi = {10.1002/anie.202108405}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256529}, pages = {20776-20780}, year = {2021}, abstract = {The reduction of a cyclic alkyl(amino)carbene (CAAC)-stabilized organoberyllium chloride yields the first neutral beryllium radical, which was characterized by EPR, IR, UV/Vis spectroscopy and X-ray crystallography. DFT calculations show significant spin density at beryllium and confirm donor-acceptor bonding between an alkylberyllium radical fragment and a neutral CAAC ligand.}, language = {en} } @article{FoehrenbacherKrahfussZapfetal.2021, author = {F{\"o}hrenbacher, Steffen A. and Krahfuss, Mirjam J. and Zapf, Ludwig and Friedrich, Alexandra and Ignat'ev, Nikolai V. and Finze, Maik and Radius, Udo}, title = {Tris(pentafluoroethyl)difluorophosphorane: a versatile fluoride acceptor for transition metal chemistry}, series = {Chemistry Europe}, volume = {27}, journal = {Chemistry Europe}, number = {10}, doi = {10.1002/chem.202004885}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256665}, pages = {3504-3516}, year = {2021}, abstract = {Fluoride abstraction from different types of transition metal fluoride complexes [L\(_n\)MF] (M=Ti, Ni, Cu) by the Lewis acid tris(pentafluoroethyl)difluorophosphorane (C\(_2\)F\(_5\))\(_3\)PF\(_2\) to yield cationic transition metal complexes with the tris(pentafluoroethyl)trifluorophosphate counterion (FAP anion, [(C\(_2\)F\(_5\))\(_3\)PF\(_3\)]\(^-\)) is reported. (C\(_2\)F\(_5\))\(_3\)PF\(_2\) reacted with trans-[Ni(iPr\(_2\)Im)\(_2\)(Ar\(^F\))F] (iPr2Im=1,3-diisopropylimidazolin-2-ylidene; Ar\(^F\)=C\(_6\)F\(_5\), 1 a; 4-CF\(_3\)-C\(_6\)F\(_4\), 1 b; 4-C\(_6\)F\(_5\)-C\(_6\)F\(_4\), 1 c) through fluoride transfer to form the complex salts trans-[Ni(iPr\(_2\)Im)\(_2\)(solv)(Ar\(^F\))]FAP (2 a-c[solv]; solv=Et\(_2\)O, CH\(_2\)Cl\(_2\), THF) depending on the reaction medium. In the presence of stronger Lewis bases such as carbenes or PPh\(_3\), solvent coordination was suppressed and the complexes trans-[Ni(iPr\(_2\)Im)\(_2\)(PPh\(_3\))(C\(_6\)F\(_5\))]FAP (trans-2 a[PPh\(_3\)]) and cis-[Ni(iPr\(_2\)Im)\(_2\)(Dipp\(_2\)Im)(C\(_6\)F\(_5\))]FAP (cis-2 a[Dipp\(_2\)Im]) (Dipp\(_2\)Im=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were isolated. Fluoride abstraction from [(Dipp\(_2\)Im)CuF] (3) in CH\(_2\)Cl\(_2\) or 1,2-difluorobenzene led to the isolation of [{(Dipp\(_2\)Im)Cu}\(_2\)]\(^2\)\(^+\)2 FAP\(^-\) (4). Subsequent reaction of 4 with PPh\(_3\) and different carbenes resulted in the complexes [(Dipp\(_2\)Im)Cu(LB)]FAP (5 a-e, LB=Lewis base). In the presence of C6Me6, fluoride transfer afforded [(Dipp\(_2\)Im)Cu(C\(_6\)Me\(_6\))]FAP (5 f), which serves as a source of [(Dipp\(_2\)Im)Cu)]\(^+\). Fluoride abstraction of [Cp\(_2\)TiF\(_2\)] (7) resulted in the formation of dinuclear [FCp\(_2\)Ti(μ-F)TiCp\(_2\)F]FAP (8) (Cp=η\(^5\)-C\(_5\)H\(_5\)) with one terminal fluoride ligand at each titanium atom and an additional bridging fluoride ligand.}, language = {en} } @article{HagspielArrowsmithFantuzzietal.2021, author = {Hagspiel, Stephan and Arrowsmith, Merle and Fantuzzi, Felipe and Vargas, Alfredo and Rempel, Anna and Hermann, Alexander and Br{\"u}ckner, Tobias and Braunschweig, Holger}, title = {Highly colored boron-doped thiazolothiazoles from the reductive dimerization of boron isothiocyanates}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {12}, doi = {10.1002/anie.202015508}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256432}, pages = {6446-6450}, year = {2021}, abstract = {Reduction of (CAAC)BBr\(_2\)(NCS) (CAAC=cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E/Z-isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)-stabilized, boron-doped, aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates.}, language = {en} } @article{HagspielFantuzziDewhurstetal.2021, author = {Hagspiel, Stephan and Fantuzzi, Felipe and Dewhurst, Rian D. and G{\"a}rtner, Annalena and Lindl, Felix and Lamprecht, Anna and Braunschweig, Holger}, title = {Adducts of the parent boraphosphaketene H\(_2\)BPCO and their decarbonylative insertion chemistry}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {24}, doi = {10.1002/anie.202103521}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256470}, pages = {13666-13670}, year = {2021}, abstract = {The first examples of Lewis base adducts of the parent boraphosphaketene (H\(_2\)B-PCO) and their cyclodimers are prepared. One of these adducts is shown to undergo mild decarbonylation and phosphinidene insertion into a B-C bond of a borole, forming very rare examples of 1,2-phosphaborinines, B/P isosteres of benzene. The strong donor properties of these 1,2-phosphaborinines are confirmed by the synthesis of their π complexes with the Group 6 metals.}, language = {en} } @article{HeRauchFriedrichetal.2021, author = {He, Jiang and Rauch, Florian and Friedrich, Alexandra and Krebs, Johannes and Krummenacher, Ivo and Bertermann, R{\"u}diger and Nitsch, J{\"o}rn and Braunschweig, Holger and Finze, Maik and Marder, Todd B.}, title = {Phenylpyridyl-fused boroles: a unique coordination mode and weak B-N coordination-induced dual fluorescence}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {9}, doi = {10.1002/anie.202013692}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256423}, pages = {4833-4840}, year = {2021}, abstract = {Phenylpyridyl-fused boroles [TipPBB1]\(_4\) and TipPBB2 were synthesized and their properties investigated. [TipPBB1]\(_4\) forms a tetramer in both the solid state and solution. TipPBB2 contains a 4-coordinate boron atom in the solid state but dissociates to give a 3-coordinate boron species in solution. TipPBB2 shows interesting temperature-dependent dual fluorescence in solution because of the equilibrium between 3- and 4-coordinate boron species due to weak N⋅⋅⋅B intermolecular coordination.}, language = {en} } @article{KoleMerzAmaretal.2021, author = {Kole, Goutam Kumar and Merz, Julia and Amar, Anissa and Fontaine, Bruno and Boucekkine, Abdou and Nitsch, J{\"o}rn and Lorenzen, Sabine and Friedrich, Alexandra and Krummenacher, Ivo and Košćak, Marta and Braunschweig, Holger and Piantanida, Ivo and Halet, Jean-Fran{\c{c}}ois and M{\"u}ller-Buschbaum, Klaus and Marder, Todd B.}, title = {2- and 2,7-substituted para-N-methylpyridinium pyrenes: syntheses, molecular and electronic structures, photophysical, electrochemical, and spectroelectrochemical properties and binding to double-stranded (ds) DNA}, series = {Chemistry - A European Journal}, volume = {27}, journal = {Chemistry - A European Journal}, number = {8}, doi = {10.1002/chem.202004748}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256642}, pages = {2837-2853}, year = {2021}, abstract = {Two N-methylpyridinium compounds and analogous N-protonated salts of 2- and 2,7-substituted 4-pyridyl-pyrene compounds were synthesised and their crystal structures, photophysical properties both in solution and in the solid state, electrochemical and spectroelectrochemical properties were studied. Upon methylation or protonation, the emission maxima are significantly bathochromically shifted compared to the neutral compounds, although the absorption maxima remain almost unchanged. As a result, the cationic compounds show very large apparent Stokes shifts of up to 7200 cm\(^{-1}\). The N-methylpyridinium compounds have a single reduction at ca. -1.5 V vs. Fc/Fc\(^+\) in MeCN. While the reduction process was reversible for the 2,7-disubstituted compound, it was irreversible for the mono-substituted one. Experimental findings are complemented by DFT and TD-DFT calculations. Furthermore, the N-methylpyridinium compounds show strong interactions with calf thymus (ct)-DNA, presumably by intercalation, which paves the way for further applications of these multi-functional compounds as potential DNA-bioactive agents.}, language = {en} } @article{LiuKoleBudimanetal.2021, author = {Liu, Zhiqiang and Kole, Goutam Kumar and Budiman, Yudha P. and Tian, Ya-Ming and Friedrich, Alexandra and Luo, Xiaoling and Westcott, Stephen A. and Radius, Udo and Marder, Todd B.}, title = {Transition metal catalyst-free, base-promoted 1,2-additions of polyfluorophenylboronates to aldehydes and ketones}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {30}, doi = {10.1002/anie.202103686}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256487}, pages = {16529-16538}, year = {2021}, abstract = {A novel protocol for the transition metal-free 1,2-addition of polyfluoroaryl boronate esters to aldehydes and ketones is reported, which provides secondary alcohols, tertiary alcohols, and ketones. Control experiments and DFT calculations indicate that both the ortho-F substituents on the polyfluorophenyl boronates and the counterion K\(^+\) in the carbonate base are critical. The distinguishing features of this procedure include the employment of commercially available starting materials and the broad scope of the reaction with a wide variety of carbonyl compounds giving moderate to excellent yields. Intriguing structural features involving O-H⋅⋅⋅O and O-H⋅⋅⋅N hydrogen bonding, as well as arene-perfluoroarene interactions, in this series of racemic polyfluoroaryl carbinols have also been addressed.}, language = {en} } @article{LuJayaramanFantuzzietal.2022, author = {Lu, Wei and Jayaraman, Arumugam and Fantuzzi, Felipe and Dewhurst, Rian D. and H{\"a}rterich, Marcel and Dietz, Maximilian and Hagspiel, Stephan and Krummenbacher, Ivo and Hammond, Kai and Cui, Jingjing and Braunschweig, Holger}, title = {An unsymmetrical, cyclic diborene based on a chelating CAAC ligand and its small-molecule activation and rearrangement chemistry}, series = {Angewandte Chemie International Edition}, volume = {61}, journal = {Angewandte Chemie International Edition}, number = {3}, doi = {10.1002/anie.202113947}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256576}, year = {2022}, abstract = {A one-pot synthesis of a CAAC-stabilized, unsymmetrical, cyclic diborene was achieved via consecutive two-electron reduction steps from an adduct of CAAC and B\(_2\)Br\(_4\)(SMe\(_2\))\(_2\). Theoretical studies revealed that this diborene has a considerably smaller HOMO-LUMO gap than those of reported NHC- and phosphine-supported diborenes. Complexation of the diborene with [AuCl(PCy\(_3\))] afforded two diborene-Au\(^I\) π complexes, while reaction with DurBH\(_2\), P\(_4\) and a terminal acetylene led to the cleavage of B-H, P-P, and C-C π bonds, respectively. Thermal rearrangement of the diborene gave an electron-rich cyclic alkylideneborane, which readily coordinated to Ag\(^I\) via its B=C double bond.}, language = {en} } @article{RamlerFantuzziGeistetal.2021, author = {Ramler, Jaqueline and Fantuzzi, Felipe and Geist, Felix and Hanft, Anna and Braunschweig, Holger and Engels, Bernd and Lichtenberg, Crispin}, title = {The dimethylbismuth cation: entry into dative Bi-Bi bonding and unconventional methyl exchange}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, doi = {10.1002/anie.202109545}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256543}, pages = {24388-24394}, year = {2021}, abstract = {The dimethyl bismuth cation, [BiMe\(_2\)(SbF\(_6\))], has been isolated and characterized. Reaction with BiMe\(_3\) allows access to the first compound featuring Bi→Bi donor-acceptor bonding. In solution, dynamic behavior with methyl exchange via an unusual S\(_E\)2 mechanism is observed, underlining the unique properties of bismuth species as soft Lewis acids with the ability to undergo reversible Bi-C bond cleavage.}, 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{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} }