TY - JOUR A1 - Lindl, Felix A1 - Lamprecht, Anna A1 - Arrowsmith, Merle A1 - Khitro, Eugen A1 - Rempel, Anna A1 - Dietz, Maximilian A1 - Wellnitz, Tim A1 - Bélanger‐Chabot, Guillaume A1 - Stoy, Andreas A1 - Paprocki, Valerie A1 - Prieschl, Dominik A1 - Lenczyk, Carsten A1 - Ramler, Jacqueline A1 - Lichtenberg, Crispin A1 - Braunschweig, Holger T1 - Aromatic 1,2‐Azaborinin‐1‐yls as Electron‐Withdrawing Anionic Nitrogen Ligands for Main Group Elements JF - Chemistry – A European Journal N2 - The 2‐aryl‐3,4,5,6‐tetraphenyl‐1,2‐azaborinines 1‐EMe\(_{3}\) and 2‐EMe\(_{3}\) (E=Si, Sn; aryl=Ph (1), Mes (=2,4,6‐trimethylphenyl, 2)) were synthesized by ring‐expansion of borole precursors with N\(_{3}\)EMe\(_{3}\)‐derived nitrenes. Desilylative hydrolysis of 1‐ and 2‐SiMe\(_{3}\) yielded the corresponding N‐protonated azaborinines, which were deprotonated with nBuLi or MN(SiMe\(_{3}\))\(_{2}\) (M=Na, K) to the corresponding group 1 salts, 1‐M and 2‐M. While the lithium salts crystallized as monomeric Lewis base adducts, the potassium salts formed coordination polymers or oligomers via intramolecular K⋅⋅⋅aryl π interactions. The reaction of 1‐M or 2‐M with CO\(_{2}\) yielded N‐carboxylate salts, which were derivatized by salt metathesis to methyl and silyl esters. Salt metathesis of 1‐M or 2‐M with methyl triflate, [Cp*BeCl] (Cp*=C\(_{5}\)Me\(_{5}\)), BBr\(_{2}\)Ar (Ar=Ph, Mes, 2‐thienyl), ECl\(_{3}\) (E=B, Al, Ga) and PX\(_{3}\) (X=Cl, Br) afforded the respective group 2, 13 and 15 1,2‐azaborinin‐2‐yl complexes. Salt metathesis of 1‐K with BBr\(_{3}\) resulted not only in N‐borylation but also Ph‐Br exchange between the endocyclic and exocyclic boron atoms. Solution \(^{11}\)B NMR data suggest that the 1,2‐azaborinin‐2‐yl ligand is similarly electron‐withdrawing to a bromide. In the solid state the endocyclic bond length alternation and the twisting of the C\(_{4}\)BN ring increase with the sterics of the substituents at the boron and nitrogen atoms, respectively. Regression analyses revealed that the downfield shift of the endocyclic \(^{11}\)B NMR resonances is linearly correlated to both the degree of twisting of the C\(_{4}\)BN ring and the tilt angle of the N‐substituent. Calculations indicate that the 1,2‐azaborinin‐1‐yl ligand has no sizeable π‐donor ability and that the aromaticity of the ring can be subtly tuned by the electronics of the N‐substituent. KW - 1,2-azaborinine KW - aromaticity KW - crystallographic analyses KW - N-functionalization KW - salt metathesis Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312222 VL - 29 IS - 11 ER - TY - JOUR A1 - Härterich, Marcel A1 - Matler, Alexander A1 - Dewhurst, Rian D. A1 - Sachs, Andreas A1 - Oppel, Kai A1 - Stoy, Andreas A1 - Braunschweig, Holger T1 - A step-for-step main-group replica of the Fischer carbene synthesis at a borylene carbonyl JF - Nature Communications N2 - The Fischer carbene synthesis, involving the conversion of a transition metal (TM)-bound CO ligand to a carbene ligand of the form [=C(OR’)R] (R, R’ = organyl groups), is one of the seminal reactions in the history of organometallic chemistry. Carbonyl complexes of p-block elements, of the form [E(CO)n] (E = main-group fragment), are much less abundant than their TM cousins; this scarcity and the general instability of low-valent p-block species means that replicating the historical reactions of TM carbonyls is often very difficult. Here we present a step-for-step replica of the Fischer carbene synthesis at a borylene carbonyl involving nucleophilic attack at the carbonyl carbon followed by electrophilic quenching at the resultant acylate oxygen atom. These reactions provide borylene acylates and alkoxy-/silyloxy-substituted alkylideneboranes, main-group analogues of the archetypal transition metal acylate and Fischer carbene families, respectively. When either the incoming electrophile or the boron center has a modest steric profile, the electrophile instead attacks at the boron atom, leading to carbene-stabilized acylboranes – boron analogues of the well-known transition metal acyl complexes. These results constitute faithful main-group replicas of a number of historical organometallic processes and pave the way to further advances in the field of main-group metallomimetics. KW - chemical bonding KW - ligands Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-357270 VL - 14 ER - TY - JOUR A1 - Ramler, Jacqueline A1 - Schwarzmann, Johannes A1 - Stoy, Andreas A1 - Lichtenberg, Crispin T1 - Two Faces of the Bi−O Bond: Photochemically and Thermally Induced Dehydrocoupling for Si−O Bond Formation JF - European Journal of Inorganic Chemistry N2 - The diorgano(bismuth)alcoholate [Bi((C\(_{6}\)H\(_{4}\)CH\(_{2}\))\(_{2}\)S)OPh] (1-OPh) has been synthesized and fully characterized. Stoichiometric reactions, UV/Vis spectroscopy, and (TD-)DFT calculations suggest its susceptibility to homolytic and heterolytic Bi−O bond cleavage under given reaction conditions. Using the dehydrocoupling of silanes with either TEMPO or phenol as model reactions, the catalytic competency of 1-OPh has been investigated (TEMPO=(tetramethyl-piperidin-1-yl)-oxyl). Different reaction pathways can deliberately be addressed by applying photochemical or thermal reaction conditions and by choosing radical or closed-shell substrates (TEMPO vs. phenol). Applied analytical techniques include NMR, UV/Vis, and EPR spectroscopy, mass spectrometry, single-crystal X-ray diffraction analysis, and (TD)-DFT calculations. KW - Bismuth KW - dehydrocoupling KW - radical reactions KW - chalcogens KW - catalysis Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257428 VL - 2022 IS - 7 ER - TY - THES A1 - Stoy, Andreas T1 - Darstellung, Charakterisierung und Reaktivität von NHC-stabilisierten 1,2-Dihalogendiborenen T1 - Preparation, characterization and reactivity of NHC-stabilized 1,2-dihalodiborenes N2 - Im Rahmen der vorliegenden Arbeit konnte eine Reihe symmetrischer und asymmetrischer Tetrahalogendiboran(4)-Addukte realisiert werden. Die symmetrischen Brom-substituierten Vertreter 19 und 102–107 waren durch quantitativen Ligandenaustausch der schwach gebundenen Lewis-Base SMe2 von 101 zugänglich. Im Falle der IDip-stabilisierten Addukte 108 bzw. 109a/b gelang die Darstellung in sehr guten Ausbeuten durch direkte Umsetzung von freiem Carben mit den Tetrahalogendiboran(4)-Vorstufen 1 (X = Cl) bzw. 2 (X = I). Die asymme¬trischen Vertreter 113a–116b konnten durch sukzessive Adduktbildung ausgehend von 1 bzw. 6 mit cAAC und dem jeweiligen NHC bei tiefen Temperaturen (−78 °C) in moderaten bis guten Ausbeuten dargestellt werden. Nachfolgende Reduktionsversuche der asymmetrischen Addukte 113a/b und 114b–116b waren von mäßigem Erfolg geprägt. Als Reduktionsmittel wurden Alkali- bzw. Erdalkalimetalle, Interkallationsverbindungen und Übergangsmetallkomplexe eingesetzt. Zwar war in allen Fällen eine deutliche Farbänderung beobachtbar, die, zusammen mit den beobachteten Resonanzen in den 11B-NMR-Spektren, die Synthese von asymmetrischen Diborenen nahelegten, jedoch gelang die Isolierung der Diborene nicht. Hierbei gestaltete sich die Abtrennung der gebildeten Nebenprodukte als problematisch. Deutlich selektiver verliefen hingegen die Reduktionen der symmetrischen Tetrahalogen-diboran(4)-Bis(Addukte) mit NaNaph bei tiefen Temperaturen (−78 °C). Hierbei gelang es, das Portfolio der bereits bekannten Vertreter dieser Substanzklasse zu erweitern. So konnten die Brom-substituierten Diborene 126–128 erstmals vollständig charakterisiert werden. Der Einfluss der Halogenatome auf die chemischen und physikalischen Eigenschaften der Diborene wurde ferner an zwei Beispielen der IDip-stabilisierten Diborene 129 und 130 untersucht. Bei identischem NHC, aber unterschiedlichen Halogenen, konnten die Eigenschaften der Diborene 21, 129 und 130 näher untersucht und miteinander verglichen werden. Besonders deutlich werden die Redoxeigenschaften der Diborene von der Art des gebundenen Halogens beeinflusst, wie cyclovoltammetrische Untersuchungen belegen. Alle NHC-stabilisierten 1,2 Dihal¬ogen¬diborene konnten ferner anhand ihrer physikalischen Eigenschaften eingeordnet und miteinander verglichen werden. Neben der Synthese und Charakterisierung neuartiger Diborene wurden auch verschiedene Reaktivitätsstudien durchgeführt. So konnten die Diborene 21, 123, 126 und 129 mit CO2 unter milden Bedingungen umgesetzt werden, wobei verschiedene Reaktionsprodukte nachgewiesen wurden. Der initiale Schritt umfasste in allen Fällen eine [2+2]-Cycloaddition die zu den Dibora-β-Lactonen 131a–134a führte, von denen 131a und 132a vollständig charakterisiert werden konnten. Im weiteren Reaktionsverlauf wurden jedoch Isomerisierungsreaktionen von 132a–134a bei Raum¬temperatur beobachtet, wobei die 2,4 Diboraoxetan 3 one 132b–134b isoliert wurden. Bedingt durch die verhältnismäßig langsame Umsetzung von 21 zu 132a konnte die [2+2] Cyclo¬addition mittels 1H-VT-NMR-Spektroskopie verfolgt werden, wobei die Rückgrat¬protonen der NHCs als selektive Sonde dienten. Eine bemerkenswert hohe Stabilität konnte für 131a bei Raumtemperatur beobachtet werden, bei der keine Anzeichen einer Umlagerung nachweisbar waren. Die angefertigten quantenchemischen Untersuchungen zum Reaktions¬mechanismus legen eine höhere Energiebarriere des Schlüsselschrittes der Umlagerungs¬reaktion für 131a als für 132a nahe, womit die Stabilität von 131a erklärbar ist. Ferner konnten beim Erhitzen von 131a für 16 Stunden auf 60 °C kurzlebige Intermediate in Form eines Oxoborans und Borylens, die im Laufe der Isomerisierungsreaktion der Dibora-β-Lactonen zu den 2,4 Diboraoxetan 3 onen auftreten, 11B NMR-spektroskopisch nachgewiesen werden. Hierdurch wurde ein weiteres Indiz gewonnen, dass die Richtigkeit des postulierten Reaktionsmechanimus verdeutlicht. Die reduzierende Wirkung der Diborene konnte mit der Darstellung von Radikalkationen demonstriert werden. Hierbei erfolgte die Umsetzung der Diborene 21, 123–126 und 128 mit [C7H7][BArF4] zu 138–143 in guten bis sehr guten Ausbeuten. Die gebildeten Radikale konnten vollständig charakterisiert werden und sind wegen ihrer Eigen¬schaften gut mit bereits literaturbekannten Vertretern dieser Substanzklasse vergleichbar. Versuche die Radikalkationen durch Umsetzung der Diborene mit [C7H7][BF4] darzustellen scheiterten an der Zersetzung während der Aufarbeitung, wodurch die Wichtigkeit des schwach koordinierenden Anions verdeutlich wird. Entgegen der Erwartungen wurden beim Vergleich der ESR-Spektren der dargestellten Radikalkationen mit bekannten Analoga deutlich unterschiedliche giso-Werte ermittelt, die auf den starken Einfluss der Bromatome zurückzuführen sind. Des Weiteren war es möglich, eine Korrelation zwischen den Strukturparametern in der Festphase und den UV/Vis-Absorptionsmaxima in Lösung nachzuweisen, wonach für diejenigen Radikale die stärkste Blauverschiebung beobachtet wurde, die den größten Diederwinkel α, zwischen den B2Br2-Ebenen und den CN2C2-Carben-ebenen, aufwiesen. In weiteren Studien wurden die Redoxeigenschaften der Diborene durch Umsetzung von 21 und 123–125 mit elementaren Chalkogenen unter milden Reaktionsbedingungen untersucht. So konnten durch Umsetzung der Diborene mit elementarem Schwefel die Diborathiirane 144–147 in moderaten bis guten Ausbeuten erhalten werden. Trotz eines großen Überschusses an Schwefel wurde aber keine vollständige BB-Bindungsspaltung beobachtet. Auf analoge Weise wurden die Diboraselenirane 148, 150 und 151 durch Umsetzung mit rotem Selen in moderaten bis guten Ausbeuten synthetisiert. Deutliche Unterschiede zeigten sich aber beim IDep-stabilisierten Diboren 123, das ein radikalisches Seleniran ausbildete. Überschüs¬siges Selen begünstigt vermutlich eine Folgeoxidation des in situ gebildeten Diboraselenirans, die jedoch für die anderen Verbindungen dieser Substanzklasse nicht beobachtbar war. Interessanterweise wurde bei allen Dipp-substituierten Verbindungen (Diborathiirane 144 und 146 sowie Dibora¬selenirane 148 und 151) das Fehlen einer Dipp-Gruppe der stabilisierten NHC-Basen im 1H NMR-Spektrum nachgewiesen. Dieser Umstand konnte durch eine eingeschränkte Rotation um die BC-Bindungsachse mittels 1H-VT-NMR-Spektrum aufgeklärt werden, wobei die Rotationsbarriere exemplarisch für 144 13.9 ± 1 kcal/mol beträgt. Eine bemerkenswerte Reaktivität der 1,2-Dibromdiborene 21 und 123–126 wurde gegenüber hetero¬aroma¬tischer Stickstoffbasen beobachtet. Mit einem großen Überschuss an Pyridin konnte ein Bromidanion aus den Diborenen verdrängt werden, wodurch die Diborenkationen 154–158 in moderaten bis guten Ausbeuten erhalten wurden. Die Abtrennung der dabei unvermeidlich gebildeten NHC-Salze gestaltete sich als schwierig, allerdings gelang es, nach einer in situ Deprotonierung mit NaHMDS die freien NHCs zu entfernen. Versuche der Deri-vatisierung mit anderen aromatischen Basen wie 2- bzw. 4-Picolin, Chinolin oder 2,2’-und 4,4’-Bipyridin scheiterten. Erfolgreich konnte DMAP eingesetzt werden, wodurch es möglich war, die Diborenkationen 160–162 in guten bis sehr guten Ausbeuten zu erhalten. Interessanterweise zeigen 154–158 teils deutliche solvatochrome Absorptions¬eigenschaften in den UV/Vis-Spektren. Im Laufe der Umsetzung von 125 mit Pyridin konnte durch angepasste Reaktions¬bedingungen das Dikation 159 in moderaten Ausbeuten isoliert werden. Dessen bemerkenswerte Stabilität zeigte sich durch eine ausgeprägte Widerstands¬fähigkeit gegenüber Sauerstoff und Luftfeuchtigkeit über mehrere Wochen. Weiterführende Unter¬suchungen der Festkörperstruktur von 159 zeigen Bindungsparameter, die trotz der ionischen Natur der Verbindung, nur geringfügig von denen des neutralen Diborens 125 abweichen. Mittels Raman-Spektroskopie konnten des Weiteren die BB-Bindungsstärke in 159 näher bestimmt werden, die mit einer Kraftkonstante von 470 N/m nahezu identisch zu der des neutralen Dibores (465 N/m) ist, was Rückschlüsse auf die Lokalisierung der positiven Ladungen auf den Pyridinringen zulässt. Aus diesem Grund kann Verbindung 159 als bis dato einziges Beispiel eines luft- und feuchtigkeitsstabilen Diborens bezeichnet werden. N2 - Within the scope of this work, a series of symmetrical and unsymmetrical tetrahalodiborane(4) adducts were synthesized. The symmetrical, bromine-substituted compounds 19 and 102–107 were accessible by quantitative ligand exchange of the weakly-bound Lewis base SMe2 in 101. The IDip-stabilized adducts 108 and 109a/b, were prepared in excellent yields by direct addition of free carbene to the tetrahalodiborane(4) precursors 1 (X = Cl), and 2 (X = I), and respectively, the unsymmetrical adducts 113a–116b could be prepared in moderate to good yields by stepwise addition of cAAC and the corresponding NHC to 1 or 6 at low temperatures (−78 °C). Subsequent attempts to reduce the asymmetric adducts 113a/b and 114b–116b with reagents such as alkali, or alkaline earth metals, intercalation compounds, and transition metal complexes were moderately successful. Although a change in colour was observed in all cases, which, together with the observed resonances in the 11B-NMR spectra, suggested the synthesis of unsymmetrical diborenes, their isolation was unsuccessful. Here, the separation of the byproducts proved to be problematic. In contrast, the reductions of the symmetrical tetrahalodiborane(4) bis(adducts) with NaNaph at low temperatures (−78 °C) were much more selective. Here, we succeeded in expanding the scope of known representatives of this substance class. Thus, the bromine-substituted diborenes 126–128 could be fully characterized for the first time. The influence of the halides on the chemical and physical properties of the diborenes were further investigated using two examples of IDip-stabilized diborenes 129 and 130. The properties of 21, 129 and 130, which represent diborenes with identical NHCs but different halides, were studied in more detail and compared with each other. The redox properties of the diborenes are particularly influenced by the nature of the halide, as emphasized by cyclo¬voltammetric studies. All NHC-stabilized 1,2-dihalodiborenes were also classified and compared with each other based on their physical properties. In addition to the synthesis and characterization of novel diborenes, a range of reactivity studies were also performed. For example, when diborenes 21, 123, 126, and 129 were reacted with CO2 under mild conditions, a variety of products were obtained. In all cases the initial step involved a [2+2] cycloaddition leading to the dibora-β-lactones 131a–134a, of which 131a and 132a were fully characterized. However, in the further course of the reaction, isomerization of 132a–134a took place, leading to the formation of the 2,4-diboraoxetane-3-ones 132b–134b. Thanks to the relatively slow conversion of 21 to 132a, the [2+2] cycloaddition could be monitored by variable-temperature 1H-NMR spectroscopy, with the backbone protons of the NHCs serving as viable probes. A remarkably high stability at room temperature was observed for 131a with no evidence of rearrangement. Quantum chemical studies of the reaction mechanism suggested a higher energy barrier for the key step of the rearrangement reaction for 131a relative to that of 132a. Furthermore, heating of 131a to 60 °C for 16 h led to the formation of short-lived intermediates in the form of an oxoborane and borylene, which occur in the course of the isomerization reaction of the dibora-β-lactones to the 2,4-diboraoxetane-3-one, and were detected by 11B-NMR spectroscopy. This provided a further indication that the postulated reaction mechanism is correct. The reducing properties of the diborenes were demonstrated by the preparation of the radical cations. Here, diborenes 21, 123–126, and 128 reacted with [C7H7][BArF4] to form 138–143 in good to excellent yields. The isolated radicals were fully characterized, and their properties are readily comparable with previously-reported representatives of this substance class. Attempts to prepare the radical cations by reacting diborenes with [C7H7][BF4] were accompanied by decomposition during workup, thus highlighting the importance of the weakly coordinating anion. Contrary to expectations, significantly different giso values were obtained when comparing the EPR spectra of the presented radical cations with known analogues, which could be attributed to the strong influence of the bromide atoms. Furthermore, it was possible to find a correlation between the structural parameters in the solid state and the UV/Vis absorption maxima in solution. The strongest blue shift was observed for those radicals that exhibited the largest dihedral angle α between the B2Br2 plane and the CN2C2-carbene planes. In further studies, the redox properties of diborenes were investigated by reacting 21 and 123–125 with elemental chalcogens under mild reaction conditions. This way, reaction of diborenes with elemental sulphur led to the formation of diborathiiranes 144–147 in moderate to good yields. Despite a large excess of sulphur, complete BB bond cleavage was not observed for any of these products. Analogously, diboraseleniranes 148, 150, and 151 were synthesized by reaction with red selenium in moderate to good yields. However, apparent differences were seen for the IDep-stabilized diborene 123, which in contrast to 21, 124 and 125 formed a radical diboraselenirane. Excess selenium presumably favors a subsequent oxidation of the in-situ-formed diboraselenirane, which however, was not observed for the other compounds of this substance class. Interestingly, one Dipp-group of the stabilizing NHC bases was not detected in the proton NMR spectrum for all Dipp-substituted compounds (diborathiiranes 144 and 146, and also diboraseleniranes 148 and 151). This circumstance could be explained by an inhibited rotation around the BC axis as verified by means of variable-temperature 1H-NMR spectroscopy, the rotation barrier exemplified by that of 144, which was found to be 13.9 ± 1 kcal/mol. A remarkable reactivity of 1,2-dibromodiborenes 21 and 123–126 was observed towards hetero¬aromatic nitrogen bases. With a large excess of pyridine, a bromide anion could be displaced, giving the diborene cations 154–158 in moderate to good yields. Separation of the NHC salts inevitably formed during this process proved to be difficult, but after in situ deprotonation with NaHMDS, it was possible to remove the free NHCs due to their substantially different solubilities. Attempts at derivatization with other aromatic bases such as 2- or 4-picoline, quinolone, or 2,2'-and 4,4'-bipyridine failed. However, addition of DMAP le to a successful halide substitution, making it possible to obtain the diborene cations 160–162 in good to excellent yields. Interestingly, 154–158 furthermore show partly distinct solvatochromic absorption properties in their UV/Vis spectra. In the course of the reaction of 125 with pyridine, the dication 159 was isolated in moderate yields by employing adjusted reaction conditions. Its remarkable stability was demonstrated by a pronounced resistance to oxygen and atmospheric humidity over a period of several weeks. Further studies of the solid-state structure of 159 show binding parameters that deviate only slightly from those of the neutral diborene 125, despite the ionic nature of the compound. Furthermore, by use of Raman spectroscopy, it was possible to determine the BB bond strength in 159 in more detail, which, with a force constant of 470 N/m, is almost identical to that of the neutral diborene (465 N/m). This result allows us to draw conclusions about the localization of the positive charges on the pyridine rings. For this reason, compound 159 represents a rare example of an air- and moisture-stable diborene. KW - Bor KW - Mehrfachbindung KW - Synthese KW - Eigenschaften KW - Reaktivität KW - Diboren KW - Carben Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-237818 ER - TY - JOUR A1 - Liu, Siyuan A1 - Légaré, Marc-André A1 - Seufert, Jens A1 - Prieschl, Dominic A1 - Rempel, Anna A1 - Englert, Lukas A1 - Dellermann, Theresa A1 - Paprocki, Valerie A1 - Stoy, Andreas A1 - Braunschweig, Holger T1 - 2,2′-Bipyridyl as a Redox-Active Borylene Abstraction Agent JF - Inorganic Chemistry N2 - 2,2′-Bipyridyl is shown to spontaneously abstract a borylene fragment (R–B:) from various hypovalent boron compounds. This process is a redox reaction in which the bipyridine is reduced and becomes a dianionic substituent bound to boron through its two nitrogen atoms. Various transition metal–borylene complexes and diboranes, as a well as a diborene, take part in this reaction. In the latter case, our results show an intriguing example of the homolytic cleavage of a B═B double bond. KW - Borylene KW - Heterocycles KW - Boron KW - Main-group chemistry Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-215595 N1 - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Inorganic Chemistry, copyright © American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acs.inorgchem.0c01383. VL - 59 IS - 15 ER - TY - JOUR A1 - Brunecker, Carina A1 - Müssig, Jonas H. A1 - Arrowsmith, Merle A1 - Fantuzzi, Felipe A1 - Stoy, Andreas A1 - Böhnke, Julian A1 - Hofmann, Alexander A1 - Bertermann, Rüdiger A1 - Engels, Bernd A1 - Braunschweig, Holger T1 - Boranediyl‐ and Diborane(4)‐1,2‐diyl‐Bridged Platinum A‐Frame Complexes JF - Chemistry – A European Journal N2 - Diplatinum A‐frame complexes with a bridging (di)boron unit in the apex position were synthesized in a single step by the double oxidative addition of dihalo(di)borane precursors at a bis(diphosphine)‐bridged Pt\(^{0}\)\(_{2}\) complex. While structurally analogous to well‐known μ‐borylene complexes, in which delocalized dative three‐center‐two‐electron M‐B‐M bonding prevails, theoretical investigations into the nature of Pt−B bonding in these A‐frame complexes show them to be rare dimetalla(di)boranes displaying two electron‐sharing Pt−B σ‐bonds. This is experimentally reflected in the low kinetic stability of these compounds, which are prone to loss of the (di)boron bridgehead unit. KW - boron KW - bonding KW - EDA-NOCV KW - oxidative addition KW - platinum Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214707 VL - 26 IS - 39 SP - 8518 EP - 8523 ER - TY - INPR A1 - Englert, Lukas A1 - Stoy, Andreas A1 - Arrowsmith, Merle A1 - Müssig, Jonas H. A1 - Thaler, Melanie A1 - Deißenberger, Andrea A1 - Häfner, Alena A1 - Böhnke, Julian A1 - Hupp, Florian A1 - Seufert, Jens A1 - Mies, Jan A1 - Damme, Alexander A1 - Dellermann, Theresa A1 - Hammond, Kai A1 - Kupfer, Thomas A1 - Radacki, Krzysztof A1 - Thiess, Torsten A1 - Braunschweig, Holger T1 - Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity T2 - Chemistry - A European Journal N2 - A series of 22 new bis(phosphine), bis(carbene) and bis(isonitrile) tetrahalodiborane adducts has been synthesized, either by direct adduct formation with highly sensitive B2X4 precursors (X = Cl, Br, I) or by ligand exchange at stable B2X4(SMe2)2 precursors (X = Cl, Br) with labile dimethylsulfide ligands. The isolated compounds have been fully characterized using NMR spectroscopic, (C,H,N)- elemental and, for 20 of these compounds, X-ray crystallographic analysis, revealing an unexpected variation in the bonding motifs. Besides the classical B2X4L2 diborane(6) adducts, some of the more sterically demanding carbene ligands induce a halide displacement leading to the first halide-bridged monocationic diboron species, [B2X3L2]A (A = BCl4, Br, I). Furthermore, low-temperature 1:1 reactions of B2Cl4 with sterically demanding N-heterocyclic carbenes led to the formation of kinetically unstable mono-adducts, one of which was structurally characterized. A comparison of the NMR and structural data of new and literature-known bis-adducts shows several trends pertaining to the nature of the halides and the stereoelectronic properties of the Lewis bases employed. KW - diborane(6) KW - Lewis-base adducts KW - ligand exchange KW - crystallography KW - NMR spectroscopy Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-184888 N1 - This is the pre-peer reviewed version of the following article: L. Englert, A. Stoy, M. Arrowsmith, J. H. Muessig, M. Thaler, A. Deißenberger, A. Häfner, J. Böhnke, F. Hupp, J. Seufert, J. Mies, A. Damme, T. Dellermann, K. Hammond, T. Kupfer, K. Radacki, T. Thiess, H. Braunschweig, Chem. Eur. J. 2019, 25, 8612. https://doi.org/10.1002/chem.201901437, which has been published in final form at https://doi.org/10.1002/chem.201901437. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. ER - TY - INPR A1 - Stoy, Andreas A1 - Böhnke, Julian A1 - Jiménez-Halla, J. Oscar C. A1 - Dewhurst, Rian D. A1 - Thiess, Torsten A1 - Braunschweig, Holger T1 - CO\(_2\) Binding and Splitting by Boron–Boron Multiple Bonds T2 - Angewandte Chemie, International Edition N2 - CO\(_2\) is found to undergo room-temperature, ambient- pressure reactions with two species containing boron-boron multiple bonds, leading to incorporation of either one or two CO\(_2\) molecules. In one case, a thermally-unstable intermediate was structurally characterized, indicating the operation of an initial 2+2 cycloaddition mechanism in the reaction. KW - carbon dioxide KW - CO2 fixation KW - diborenes KW - diborynes KW - boron Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-164265 N1 - This is the pre-peer reviewed version of the following article: A. Stoy, J. Böhnke, J. O. C. Jiménez‐Halla, R. D. Dewhurst, T. Thiess, H. Braunschweig, Angew. Chem. Int.Ed. 2018, 57,5947 –5951, which has been published in final form at DOI: 10.1002/anie.201802117. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. ER - TY - JOUR A1 - Ceyman, Harald A1 - Rosspeintner, Arnulf A1 - Schreck, Maximilian H. A1 - Mützel, Carina A1 - Stoy, Andreas A1 - Vauthey, Eric A1 - Lambert, Christoph T1 - Cooperative enhancement versus additivity of two-photon-absorption cross sections in linear and branched squaraine superchromophores JF - Physical Chemistry Chemical Physics N2 - The linear and nonlinear optical properties of a series of oligomeric squaraine dyes were investigated by one-photon absorption spectroscopy (1PA) and two-photon absorption (2PA) induced fluorescence spectroscopy. The superchromophores are based on two indolenine squaraine dyes with transoid (SQA) and cisoid configuration (SQB). Using these monomers, linear dimers and trimers as well as star-shaped trimers and hexamers with benzene or triphenylamine cores were synthesised and investigated. The red-shifted and intensified 1PA spectra of all superchromophores could well be explained by exciton coupling theory. In the linear chromophore arrangements we also found superradiance of fluorescence but not in the branched systems. Furthermore, the 2PA showed enhanced cross sections for the linear oligomers but only additivity for the branched systems. This emphasizes that the enhancement of the 2PA cross section in the linear arrangements is probably caused by orbital interactions of higher excited configurations. KW - 2-photon absorption KW - Vibronic contributions KW - One-photon KW - Molecules KW - Intensity KW - Multibranched structures KW - Optical properties KW - Dyes KW - Chromophores KW - Design Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188299 VL - 18 IS - 24 ER - TY - JOUR A1 - Harkin, David J. A1 - Broch, Katharina A1 - Schreck, Maximilian A1 - Ceyman, Harald A1 - Stoy, Andreas A1 - Yong, Chaw-Keong A1 - Nikolka, Mark A1 - McCulloch, Ian A1 - Stingelin, Natalie A1 - Lambert, Christoph A1 - Sirringhaus, Henning T1 - Decoupling charge transport and electroluminescence in a high mobility polymer semiconductor JF - Advanced Materials N2 - Fluorescence enhancement of a high-mobility polymer semiconductor is achieved via energy transfer to a higher fluorescence quantum yield squaraine dye molecule on 50 ps timescales. In organic light-emitting diodes, an order of magnitude enhancement of the external quantum efficiency is observed without reduction in the charge-carrier mobility resulting in radiances of up to 5 W str\(^{-1}\) m\(^{-2}\) at 800 nm. KW - Light-emitting diodes KW - Fiels-effect transistors KW - Energy transfer KW - Conjugated polymers KW - High performance KW - High efficiency KW - Perovskite KW - Amplification KW - Fluorescence KW - Emission Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187670 VL - 28 IS - 30 ER -