@article{BrosgeLorenzHeltenetal.2019, author = {Brosge, Felix and Lorenz, Thomas and Helten, Holger and Bolm, Carsten}, title = {BN- and BO-Doped Inorganic-Organic Hybrid Polymers with Sulfoximine Core Units}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {55}, doi = {10.1002/chem.201903289}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206194}, pages = {12708-12711}, year = {2019}, abstract = {While polysulfones constitute a class of well-established, highly valuable applied materials, knowledge about polymers based on the related sulfoximine group is very limited. We have employed functionalized diaryl sulfoximines and a p -phenylene bisborane as building blocks for unprecedented BN- and BO-doped alternating inorganic-organic hybrid copolymers. While the former were accessed by a facile silicon/boron exchange protocol, the synthesis of polymers with main-chain B-O linkages was achieved by salt elimination.}, 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{BudimanFriedrichRadiusetal.2019, author = {Budiman, Yudha P. and Friedrich, Alexandra and Radius, Udo and Marder, Todd B.}, title = {Copper-catalysed Suzuki-Miyaura cross-coupling of highly fluorinated aryl boronate esters with aryl iodides and bromides and fluoroarene-arene π-stacking interactions in the products}, series = {ChemCatChem}, volume = {11}, journal = {ChemCatChem}, number = {21}, doi = {10.1002/cctc.201901220}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204839}, pages = {5387-5396}, year = {2019}, abstract = {A combination of copper iodide and phenanthroline as the ligand is an efficient catalyst for Suzuki-Miyaura cross-coupling of highly fluorinated boronate esters (aryl-Bpin) with aryl iodides and bromides to generate fluorinated biaryls in good to excellent yields. This method represents a nice alternative to traditional cross-coupling methods which require palladium catalysts and stoichiometric amounts of silver oxide. We note that π⋅⋅⋅π stacking interactions dominate the molecular packing in the partly fluorinated biaryl crystals investigated herein. They are present either between the arene and perfluoroarene, or solely between arenes or perfluoroarenes, respectively.}, language = {en} } @article{LiuMingZhangetal.2019, author = {Liu, Xiaocui and Ming, Wenbo and Zhang, Yixiao and Friedrich, Alexandra and Marder, Todd B.}, title = {Copper-Catalyzed Triboration: Straightforward, Atom-Economical Synthesis of 1,1,1-Triborylalkanes from Terminal Alkynes and HBpin}, series = {Angewandte Chemie International Edition}, volume = {58}, journal = {Angewandte Chemie International Edition}, number = {52}, doi = {10.1002/anie.201909376}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206185}, pages = {18923-18927}, year = {2019}, abstract = {A convenient and efficient one-step synthesis of 1,1,1-triborylalkanes was achieved via sequential dehydrogenative borylation and double hydroborations of terminal alkynes with HBpin (HBpin=pinacolborane) catalyzed by inexpensive and readily available Cu(OAc)\(_2\). This process proceeds under mild conditions, furnishing 1,1,1-tris(boronates) with wide substrate scope, excellent selectivity, and good functional-group tolerance, and is applicable to gram-scale synthesis without loss of yield. The 1,1,1-triborylalkanes can be used in the preparation of α-vinylboronates and borylated cyclic compounds, which are valuable but previously rare compounds. Different alkyl groups can be introduced stepwise via base-mediated deborylative alkylation to produce racemic tertiary alkyl boronates, which can be readily transformed into useful tertiary alcohols.}, language = {en} } @article{Belanger‐ChabotBraunschweig2019, author = {B{\´e}langer-Chabot, Guillaume and Braunschweig, Holger}, title = {Hexahalodiborate Dianions: A New Family of Binary Boron Halides}, series = {Angewandte Chemie International Edition}, volume = {58}, journal = {Angewandte Chemie International Edition}, number = {40}, doi = {10.1002/anie.201906666}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-219688}, pages = {14270-14274}, year = {2019}, abstract = {The electron-precise binary boron subhalide species [B\(_2\)X\(_6\)]\(^{2-}\) X=F, Br, I) were synthesized and their structures confirmed by X-ray crystallography. The existence of the previously claimed [B\(_2\)Cl\(_6\)]\(^{2-}\), which had been questioned, was also confirmed by X-ray crystallography. The dianions are isoelectronic to hexahaloethanes, are subhalide analogues of the well-known tetrahaloborate anions (BX\(_4\)\(^-\)), and are rare examples of molecular electron-precise binary boron species beyond B\(_2\)X\(_4\), BX\(_3\), and [BX\(_4\)]\(^-\).}, language = {en} } @article{BelaidiRauchZhangetal.2019, author = {Belaidi, Houmam and Rauch, Florian and Zhang, Zuolun and Latouche, Camille and Boucekkine, Abdou and Marder, Todd B. and Halet, Jean-Francois}, title = {Insights into the optical properties of triarylboranes with strongly electron-accepting bis(fluoromesityl)boryl groups: when theory meets experiment}, series = {ChemPhotoChem}, volume = {4}, journal = {ChemPhotoChem}, number = {3}, doi = {10.1002/cptc.201900256}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-205600}, pages = {173-180}, year = {2019}, abstract = {The photophysical properties (absorption, fluorescence and phosphorescence) of a series of triarylboranes of the form 4-D-C\(_6\)H\(_4\)-B(Ar)\(_2\) (D=\(^t\)Bu or NPh\(_2\); Ar=mesityl (Mes) or 2,4,6-tris(trifluoromethylphenyl (Fmes)) were analyzed theoretically using state-of-the-art DFT and TD-DFT methods. Simulated emission spectra and computed decay rate constants are in very good agreement with the experimental data. Unrestricted electronic computations including vibronic contributions explain the unusual optical behavior of 4-\(^t\)Bu-C\(_6\)H\(_4\)-B(Fmes)\(_2\) 2, which shows both fluorescence and phosphorescence at nearly identical energies (at 77 K in a frozen glass). Analysis of the main normal modes responsible for the phosphorescence vibrational fine structure indicates that the bulky tert-butyl group tethered to the phenyl ring is strongly involved. Interestingly, in THF solvent, the computed energies of the singlet and triplet excited states are very similar for compound 2 only, which may explain why 2 shows phosphorescence in contrast to the other members of the series.}, language = {en} } @article{LorkowskiKrahfussKubickietal.2019, author = {Lorkowski, Jan and Krahfuss, Mirjam and Kubicki, Maciej and Radius, Udo and Pietraszuk, Cezary}, title = {Intramolecular ring expansion reaction (RER) and intermolecular coordination of in situ generated Cyclic (Amino)(Aryl)Carbenes (cAArCs)}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, number = {48}, doi = {10.1002/chem.201902630}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204847}, pages = {11365-11374}, year = {2019}, abstract = {Cyclic (amino)(aryl)carbenes (cAArCs) based on the isoindoline core were successfully generated in situ by α-elimination of 3-alkoxyisoindolines at high temperatures or by deprotonation of isoindol-2-ium chlorides with sodium or copper(I) acetates at low temperatures. 3-Alkoxy-isoindolines 2 a ,b-OR (R=Me, Et, i Pr) have been prepared in high yields by the addition of a solution of 2-aryl-1,1-diphenylisoindol-2-ium triflate (1 a ,b-OTf ; a : aryl=Dipp=2,6-diisopropylphenyl; b : Mesityl-, Mes=2,4,6-trimethylphenyl) to the corresponding alcohol (ROH) with NEt3 at room temperature. Furthermore, the reaction of 2 a ,b-OMe in diethyl ether with a tenfold excess of hydrochloric acid led to the isolation of the isoindol-2-ium chlorides 1 a ,b-Cl in high yields. The thermally generated cAArC reacts with sulfur to form the thioamide 3 a . Without any additional trapping reagent, in situ generation of 1,1-diphenylisoidolin-3-ylidenes does not lead to the isolation of these compounds, but to the reaction products of the insertion of the carbene carbon atom into an ortho C-H bond of a phenyl substituent, followed by ring-expansion reaction; namely, anthracene derivatives 9-N(H)aryl-10-Ph-C14H8 4 a ,b (a : Dipp; b : Mes). These compounds are conveniently synthesized by deprotonation of the isoindol-2-ium chlorides with sodium acetate in high yields. Deprotonation of 1 a-Cl with copper(I) acetate at low temperatures afforded a mixture of 4 a and the corresponding cAArC copper(I) chloride 5 a , and allowed the isolation and structural characterization of the first example of a cAArC copper complex of general formula [(cAArC)CuCl].}, language = {en} } @unpublished{LegarePranckeviciusBraunschweig2019, author = {L{\´e}gar{\´e}, Marc-Andr{\´e} and Pranckevicius, Conor and Braunschweig, Holger}, title = {Metallomimetic Chemistry of Boron}, series = {Chemical Reviews}, journal = {Chemical Reviews}, doi = {10.1021/acs.chemrev.8b00561}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-186317}, year = {2019}, abstract = {The study of main-group molecules that behave and react similarly to transition-metal (TM) complexes has attracted significant interest in recent decades. Most notably, the attractive idea of replacing the all-too-often rare and costly metals from catalysis has motivated efforts to develop main-group-element-mediated reactions. Main-group elements, however, lack the electronic flexibility of TM complexes that arises from combinations of empty and filled d orbitals and that seem ideally suited to bind and activate many substrates. In this review, we look at boron, an element that despite its nonmetal nature, low atomic weight, and relative redox staticity has achieved great milestones in terms of TM-like reactivity. We show how in interelement cooperative systems, diboron molecules, and hypovalent complexes the fifth element can acquire a truly metallomimetic character. As we discuss, this character is powerfully demonstrated by the reactivity of boron-based molecules with H2, CO, alkynes, alkenes and even with N2.}, language = {en} } @article{BruecknerDewhurstDellermannetal.2019, author = {Br{\"u}ckner, Tobias and Dewhurst, Rian D. and Dellermann, Theresa and M{\"u}ller, Marcel and Braunschweig, Holger}, title = {Mild synthesis of diboryldiborenes by diboration of B-B triple bonds}, series = {Chemical Science}, volume = {10}, journal = {Chemical Science}, doi = {10.1039/C9SC02544H}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-186306}, pages = {7375-7378}, year = {2019}, abstract = {A set of diboryldiborenes are prepared by the mild, catalyst-free, room-temperature diboration of the B-B triple bonds of doubly base-stabilized diborynes. Two of the product diboryldiborenes are found to be air- and water-stable in the solid state, an effect that is attributed to their high crystallinity and extreme insolubility in a wide range of solvents.}, language = {en} } @article{HeRauchFriedrichetal.2019, author = {He, Jiang and Rauch, Florian and Friedrich, Alexandra and Sieh, Daniel and Ribbeck, Tatjana and Krummenacher, Ivo and Braunschweig, Holger and Finze, Maik and Marder, Todd B.}, title = {N-Heterocyclic Olefins as Electron Donors in Combination with Triarylborane Acceptors: Synthesis, Optical and Electronic Properties of D-π-A Compounds}, series = {Chemistry - A European Journal}, volume = {25}, journal = {Chemistry - A European Journal}, doi = {10.1002/chem.201903118}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204690}, pages = {13777-13784}, year = {2019}, abstract = {N-heterocyclic olefins (NHOs), relatives of N-heterocyclic carbenes (NHCs), exhibit high nucleophilicity and soft Lewis basic character. To investigate their π-electron donating ability, NHOs were attached to triarylborane π-acceptors (A) giving donor (D)-π-A compounds 1-3. In addition, an enamine π-donor analogue (4) was synthesized for comparison. UV-visible absorption studies show a larger red shift for the NHO-containing boranes than for the enamine analogue, a relative of cyclic (alkyl)(amino) carbenes (CAACs). Solvent-dependent emission studies indicate that 1-4 have moderate intramolecular charge-transfer (ICT) behavior. Electrochemical investigations reveal that the NHO-containing boranes have extremely low reversible oxidation potentials (e.g., for 3, \(E^{ox}_{1/2}\) =-0.40 V vs. ferrocene/ferrocenium, Fc/Fc\(^+\), in THF). Time-dependent (TD) DFT calculations show that the HOMOs of 1-3 are much more destabilized than that of the enamine-containing 4, which confirms the stronger donating ability of NHOs.}, language = {en} }