@article{BachmannHelbigCrumbachetal.2022, author = {Bachmann, Jonas and Helbig, Andreas and Crumbach, Merian and Krummenacher, Ivo and Braunschweig, Holger and Helten, Holger}, title = {Fusion of Aza- and Oxadiborepins with Furans in a Reversible Ring-Opening Process Furnishes Versatile Building Blocks for Extended π-Conjugated Materials}, series = {Chemistry - A European Journal}, volume = {28}, journal = {Chemistry - A European Journal}, number = {63}, doi = {10.1002/chem.202202455}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293926}, year = {2022}, abstract = {A modular synthesis of both difurooxa- and difuroazadiborepins from a common precursor is demonstrated. Starting from 2,2′-bifuran, after protection of the positions 5 and 5' with bulky silyl groups, formation of the novel polycycles proceeds through opening of the furan rings to a dialkyne and subsequent re-cyclization in the borylation step. The resulting bifuran-fused diborepins show pronounced stability, highly planar tricyclic structures, and intense blue light emission. Deprotection and transformation into dibrominated building blocks that can be incorporated into π-extended materials can be performed in one step. Detailed DFT calculations provide information about the aromaticity of the constituent rings of this polycycle.}, language = {en} } @article{CrumbachBachmannFritzeetal.2021, author = {Crumbach, Merian and Bachmann, Jonas and Fritze, Lars and Helbig, Andreas and Krummenacher, Ivo and Braunschweig, Holger and Helten, Holger}, title = {Dithiophene-Fused Oxadiborepins and Azadiborepins: A New Class of Highly Fluorescent Heteroaromatics}, series = {Angewandte Chemie International Edition}, volume = {60}, journal = {Angewandte Chemie International Edition}, number = {17}, doi = {10.1002/anie.202100295}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-238996}, pages = {9290 -- 9295}, year = {2021}, abstract = {Access to dithiophene-fused oxadiborepins and the first azadiborepins attained via a modular synthesis route are presented. The new compounds emit intense blue light, some of which demonstrate fluorescence quantum yields close to unity. Cyclic voltammetry (CV) revealed electrochemically reversible one-electron reduction processes. The weak aromatic character of the novel 1,2,7-azadiborepin ring is demonstrated with in-depth theoretical investigations using nucleus-independent chemical shift (NICS) scans and anisotropy of the induced current density (ACID) calculations.}, language = {en} } @article{SchorrSchopperRienschetal.2021, author = {Schorr, Fabian and Schopper, Nils and Riensch, Nicolas and Fantuzzi, Felipe and Neder, Marco and Dewhurst, Rian D. and Thiess, Thorsten and Br{\"u}ckner, Tobias and Hammond, Kai and Helten, Holger and Finze, Maik and Braunschweig, Holger}, title = {Controlled Synthesis of Oligomers Containing Main-Chain B(sp\(^{2}\))-B(sp\(^{2}\)) Bonds}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {64}, doi = {10.1002/chem.202103366}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257274}, pages = {16043-16048}, year = {2021}, abstract = {A number of novel alkynyl-functionalized diarylbis(dimethylamino)diboranes(4) are prepared by salt metathesis, and the appended alkynyl groups are subjected to hydroboration. Their reactions with monohydroboranes lead to discrete boryl-appended diborane(4) species, while dihydroboranes induce their catenation to oligomeric species, the first known examples of well-characterized macromolecular species with B-B bonds. The oligomeric species were found to comprise up to ten repeat units and are soluble in common organic solvents. Some of the oligomeric species have good air stability and all were characterized by NMR and vibrational spectroscopy and size-exclusion chromatography techniques.}, language = {en} } @unpublished{AuerhammerArrowsmithBoehnkeetal.2018, author = {Auerhammer, Dominic and Arrowsmith, Merle and B{\"o}hnke, Julian and Braunschweig, Holger and Dewhurst, Rian D. and Kupfer, Thomas}, title = {Brothers from Another Mother: a Borylene and its Dimer are Non-Interconvertible but Connected through Reactivity}, series = {Chemical Science}, journal = {Chemical Science}, doi = {10.1039/C7SC04789D}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-157125}, year = {2018}, abstract = {The self-stabilizing, tetrameric cyanoborylene [(cAAC)B(CN)]4 (I, cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) and its diborene relative, [(cAAC)(CN)B=B(CN)(cAAC)] (II), both react with disulfides and diselenides to yield the corresponding cAAC-supported cyanoboron bis(chalcogenides). Furthermore, reactions of I or II with elemental sulfur and selenium in various stoichiometries provided access to a variety of cAAC- stabilized cyanoboron-chalcogen heterocycles, including a unique dithiaborirane, a diboraselenirane, 1,3-dichalcogena-2,4-diboretanes, 1,3,4-trichalcogena- 2,5-diborolanes and a rare six-membered 1,2,4,5-tetrathia-3,6-diborinane. Stepwise addition reactions and solution stability studies provided insights into the mechanism of these reactions and the subtle differences in reactivity observed between I and II.}, language = {en} } @unpublished{BoehnkeBraunschweigJimenezHallaetal.2018, author = {B{\"o}hnke, Julian and Braunschweig, Holger and Jim{\´e}nez-Halla, Oscar and Krummenacher, Ivo and Stennett, Tom E.}, title = {Half-Sandwich Complexes of an Extremely Electron-Donating, Re-dox-Active η\(^6\)-Diborabenzene Ligand}, series = {Journal of the American Chemical Society}, journal = {Journal of the American Chemical Society}, doi = {10.1021/jacs.7b12394}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-156766}, year = {2018}, abstract = {The heteroarene 1,4-bis(CAAC)-1,4-diborabenzene (1; CAAC = cyclic (alkyl)(amino)carbene) reacts with [(MeCN)\(_3\)M(CO)\(_3\)] (M = Cr, Mo, W) to yield half-sandwich complexes of the form [(η\(^6\)-diborabenzene)M(CO)\(_3\)] (M = Cr (2), Mo (3), W (4)). Investigation of the new complexes with a combination of X-ray diffraction, spectroscopic methods and DFT calculations shows that ligand 1 is a remarkably strong electron donor. In particular, [(η\(^6\)-arene)M(CO)\(_3\)] complexes of this ligand display the lowest CO stretching frequencies yet observed for this class of complex. Cyclic voltammetry on complexes 2-4 revealed one reversi- ble oxidation and two reversible reduction events in each case, with no evidence of ring-slippage of the arene to the η\(^4\) binding mode. Treatment of 4 with lithium metal in THF led to identification of the paramagnetic complex [(1)W(CO)\(_3\)]Li·2THF (5). Compound 1 can also be reduced in the absence of a transition metal to its dianion 1\(^{2-}\), which possesses a quinoid-type structure.}, language = {en} } @unpublished{StoyBoehnkeJiménezHallaetal.2018, author = {Stoy, Andreas and B{\"o}hnke, Julian and Jiménez-Halla, J. Oscar C. and Dewhurst, Rian D. and Thiess, Torsten and Braunschweig, Holger}, title = {CO\(_2\) Binding and Splitting by Boron-Boron Multiple Bonds}, series = {Angewandte Chemie, International Edition}, journal = {Angewandte Chemie, International Edition}, doi = {10.1002/anie.201802117}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-164265}, year = {2018}, abstract = {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.}, language = {en} } @unpublished{ArrowsmithMattockBoehnkeetal.2018, author = {Arrowsmith, Merle and Mattock, James D. and B{\"o}hnke, Julian and Krummenacher, Ivo and Vargas, Alfredo and Braunschweig, Holger}, title = {Direct access to a cAAC-supported dihydrodiborene and its dianion}, series = {Chemical Communications}, journal = {Chemical Communications}, doi = {10.1039/C8CC01580E}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-164276}, year = {2018}, abstract = {The two-fold reduction of (cAAC)BHX\(_2\) (cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene; X = Cl, Br) provides a facile, high-yielding route to the dihydrodiborene (cAAC)\(_2\)B\(_2\)H\(_2\). The (chloro)hydroboryl anion reduction intermediate was successfully isolated using a crown ether. Overreduction of the diborene to its dianion [(cAAC)\(_2\)B\(_2\)H\(_2\)]\(^{2-}\) causes a decrease in the B-B bond order whereas the B-C bond orders increase.}, language = {en} } @article{BoehnkeBruecknerHermannetal.2018, author = {B{\"o}hnke, Julian and Br{\"u}ckner, Tobias and Hermann, Alexander and Gonz{\´a}lez-Belman, Oscar F. and Arrowsmith, Merle and Jim{\´e}nez-Halla, J. Oscar C. and Braunschweig, Holger}, title = {Single and double activation of acetone by isolobal B≡N and B≡B triple bonds}, series = {Chemical Science}, volume = {9}, journal = {Chemical Science}, doi = {10.1039/c8sc01249k}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-164286}, pages = {5354-5359}, year = {2018}, abstract = {B≡N and B≡B triple bonds induce C-H activation of acetone to yield a (2-propenyloxy)aminoborane and an unsymmetrical 1-(2- propenyloxy)-2-hydrodiborene, respectively. DFT calculations showed that, despite their stark electronic differences, both the B≡N and B≡B triple bonds activate acetone via a similar coordination-deprotonation mechansim. In contrast, the reaction of acetone with a cAAC-supported diboracumulene yielded a unique 1,2,3-oxadiborole, which according to DFT calculations also proceeds via an unsymmetrical diborene, followed by intramolecular hydride migration and a second C-H activation of the enolate ligand.}, language = {en} } @unpublished{CidHermannRadcliffeetal.2018, author = {Cid, Jessica and Hermann, Alexander and Radcliffe, James E. and Curless, Liam D. and Braunschweig, Holger and Ingleson, Michael J.}, title = {Synthesis of Unsymmetrical Diboron(5) Compounds and Their Conversion to Diboron(5) Cations}, series = {Organometallics}, journal = {Organometallics}, doi = {10.1021/acs.organomet.8b00288}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-164299}, year = {2018}, abstract = {Reaction of bis-catecholatodiboron-NHC adducts, B\(_2\)Cat\(_2\)(NHC), (NHC = IMe (tetramethylimidazol-2-ylidene), IMes (1,3-dimesitylimidazol-2-ylidene) or IDIPP (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene)) with BCl3 results in the replacement of the catecholato group bound to the four coordinate boron with two chlorides to yield diboron(5) Lewis acid-base adducts of formula CatB-BCl\(_2\)(NHC). These compounds are precursors to diboron(5) monocations, accessed by adding AlCl\(_3\) or K[B(C\(_6\)F\(_5\))\(_4\)] as halide abstraction agents in the presence of a Lewis base. The substitution of the chlorides of CatB-BCl\(_2\)(NHC) for hydrides is achieved using Bu\(_3\)SnH and a halide abstracting agent to form 1,1-dihydrodiboron(5) compounds, CatB-BH\(_2\)(NHC). Attempts to generate diboron(4) monocations of formula [CatB-B(Y)(NHC)]\(^+\) (Y = Cl or H) led to the rapid formation of CatBY.}, 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{BraunschweigBruecknerDeissenbergeretal.2017, author = {Braunschweig, Holger and Br{\"u}ckner, Tobias and Deißenberger, Andrea and Dewhurst, Rian and Gackstatter, Annika and G{\"a}rtner, Annalena and Hofmann, Alexander and Kupfer, Thomas and Prieschl, Dominic and Thiess, Torsten and Wang, Sunewang Rixin}, title = {Reaction of Dihalodiboranes(4) with N-Heterocyclic Silylenes: Facile Construction of 1-Aryl-2-Silyl-1,2-Diboraindanes}, series = {Chemistry, A European Journal}, journal = {Chemistry, A European Journal}, doi = {10.1002/chem.201702377}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-153068}, year = {2017}, abstract = {Dihalodiboranes(4) react with an N-heterocyclic silylene (NHSi) to generate NHSi-adducts of 1-aryl-2-silyl-1,2-diboraindanes as confirmed by X-ray crystallography, featuring the functionalization of both B-X (X = halogen) bonds and a C-H bond under mild conditions. Coordination of a third NHSi to the proposed 1,1-diaryl- 2,2-disilyldiborane(4) intermediates, generated by a two-fold B-X insertion, may be crucial for the C-H borylation that leads to the final products. Notably, our results demonstrate the first C-H borylation with a strong B-F bond activated by silylene insertion.}, language = {en} } @unpublished{BoehnkeDellermannCeliketal.2018, author = {B{\"o}hnke, Julian and Dellermann, Theresa and Celik, Mehmet Ali and Krummenacher, Ivo and Dewhurst, Rian D. and Demeshko, Serhiy and Ewing, William C. and Hammond, Kai and Heß, Merlin and Bill, Eckhard and Welz, Eileen and R{\"o}hr, Merle I. S. and Mitric, Roland and Engels, Bernd and Meyer, Franc and Braunschweig, Holger}, title = {Isolation of diradical products of twisted double bonds}, series = {Nature Communications}, journal = {Nature Communications}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-160248}, year = {2018}, abstract = {Molecules containing multiple bonds between atoms—most often in the form of olefins—are ubiquitous in nature, commerce, and science, and as such have a huge impact on everyday life. Given their prominence, over the last few decades, frequent attempts have been made to perturb the structure and reactivity of multiply-bound species through bending and twisting. However, only modest success has been achieved in the quest to completely twist double bonds in order to homolytically cleave the associated π bond. Here, we present the isolation of double-bond-containing species based on boron, as well as their fully twisted diradical congeners, by the incorporation of attached groups with different electronic properties. The compounds comprise a structurally authenticated set of diamagnetic multiply-bound and diradical singly-bound congeners of the same class of compound.}, language = {en} } @unpublished{StennettMattockVollertetal.2018, author = {Stennett, Tom and Mattock, James and Vollert, Ivonne and Vargas, Alfredo and Braunschweig, Holger}, title = {Unsymmetrical, Cyclic Diborenes and Thermal Rearrangement to a Borylborylene}, series = {Angewandte Chemie, International Edition}, volume = {57}, journal = {Angewandte Chemie, International Edition}, doi = {10.1002/anie.201800671}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-160258}, pages = {4098-4102}, year = {2018}, abstract = {Cyclic diboranes(4) based on a chelating monoanionic, benzylphosphine linker were prepared by boron-silicon exchange between arylsilanes and B\(_2\)Br\(_4\). Coordination of Lewis bases to the remaining sp\(^2\) boron atom yielded unsymmetrical sp\(^3\)-sp\(^3\) diboranes, which were reduced with KC\(_8\) to their corresponding trans-diborenes. These compounds were studied by a combination of spectroscopic methods, X-ray diffraction and DFT calculations. PMe\(_3\)-stabilized diborene 6 was found to undergo thermal rearrangement to gem- diborene 8. DFT calculations on 8 reveal a polar boron-boron bond, and indicate that the compound is best described as a borylborylene.}, 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} } @unpublished{BoehnkeArrowsmithBraunschweig2018, author = {B{\"o}hnke, Julian and Arrowsmith, Merle and Braunschweig, Holger}, title = {Activation of a Zerovalent Diboron Compound by Desymmetrization}, series = {Journal of the American Chemical Society}, journal = {Journal of the American Chemical Society}, doi = {10.1021/jacs.8b06930}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-167983}, year = {2018}, abstract = {The desymmetrization of the cyclic (alkyl)(amino)carbene-supported diboracumulene, B\(_2\)(cAAC\(^{Me}\))\(_2\) (cAAC\(^{Me}\) = 1- (2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) by mono-adduct formation with IMe\(^{Me}\) (1,3-dimethylimidazol-2-ylidene) yields the zerovalent sp-sp\(^2\) diboron compound B\(_2\)(cAAC\(^{Me}\))\(_2\)(IMe\(^{Me}\)), which provides a versatile platform for the synthesis of novel symmetrical and unsymmetrical zerovalent sp\(^2\)-sp\(^2\) diboron compounds by adduct formation with IMe\(^{Me}\) and CO, respectively. Furthermore, B\(_2\)(cAAC\(^{Me}\))\(_2\)(IMe\(^{Me}\)) displays enhanced reactivity compared to its symmetrical precursor, undergoing spontaneous intramolecular C-H activation and facile twofold hydrogenation, the latter resulting in B-B bond cleavage and the formation of the mixed-base parent borylene, (cAAC\(^{Me}\))(IMe\(^{Me}\))BH.}, 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} } @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} } @unpublished{BruecknerStennettHessetal.2019, author = {Br{\"u}ckner, Tobias and Stennett, Tom E. and Heß, Merlin and Braunschweig, Holger}, title = {Single and Double Hydroboration of B-B Triple Bonds and Conver- gent Routes to a Cationic Tetraborane}, series = {Journal of the American Chemical Society}, journal = {Journal of the American Chemical Society}, doi = {10.1021/jacs.9b07991}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-188632}, year = {2019}, abstract = {A compound with a boron-boron triple bond is shown to undergo stepwise hydroboration reactions with catecholborane to yield an unsymmetrical hydro(boryl)diborene and a 2,3-dihydrotetraborane. Abstraction of H- from the latter compound produces an unusual cationic, planar tetraborane with a hydrogen atom bridging the central B2 moiety. Spectroscopic and crystallographic data and DFT calculations support a 'protonated diborene' structure for this compound, which can also be accessed via direct protonation of the corresponding diborene.}, language = {en} } @unpublished{MuessigThalerDewhurstetal.2019, author = {Muessig, Jonas H. and Thaler, Melanie and Dewhurst, Rian D. and Paprocki, Valerie and Seufert, Jens and Mattock, James D. and Vargas, Alfredo and Braunschweig, Holger}, title = {Phosphine-Stabilized Diiododiborenes: Isolable Diborenes with Six Labile Bonds}, series = {Angewandte Chemie, International Edition}, journal = {Angewandte Chemie, International Edition}, doi = {10.1002/anie.201814230}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-178608}, year = {2019}, abstract = {The lability of B=B, B-P and B-halide bonds is combined in the syntheses of the first diiododiborenes. In a series of reactivity tests, these diiododiborenes demonstrate cleavage of all six of their central bonds in different ways, leading to products of B=B hydrogenation and dihalogenation as well as halide exchange.}, language = {en} } @unpublished{StennettMattockPentecostetal.2018, author = {Stennett, Tom and Mattock, James and Pentecost, Leanne and Vargas, Alfredo and Braunschweig, Holger}, title = {Chelated Diborenes and their Inverse-Electron-Demand Diels- Alder Reactions with Dienes}, series = {Angewandte Chemie, International Edition}, journal = {Angewandte Chemie, International Edition}, doi = {10.1002/anie.201809217}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-178268}, year = {2018}, abstract = {A doubly base-stabilized diborane based on a benzylphosphine linker was prepared by a salt elimination reaction between 2-LiC\(_6\)H\(_4\)CH\(_2\)PCy\(_2\).Et\(_2\)O and B\(_2\)Br\(_4\). This compound was reduced with KC8 to its corresponding diborene, with the benzylphosphine forming a five-membered chelate. The diborene reacts with butadiene, 2-trimethylsiloxy-1,3-butadiene and isoprene to form 4,5-diboracyclohexenes, which interconvert between their 1,1- (geminal) and 1,2- (vicinal) chelated isomers. The 1,1-chelated diborene undergoes a halide-catalysed isomerisation into its thermodynamically favoured 1,2-isomer, which undergoes Diels-Alder reactions more slowly than the kinetic product.}, language = {en} }