@unpublished{EnglertStoyArrowsmithetal.2019, author = {Englert, Lukas and Stoy, Andreas and Arrowsmith, Merle and M{\"u}ssig, Jonas H. and Thaler, Melanie and Deißenberger, Andrea and H{\"a}fner, Alena and B{\"o}hnke, Julian and Hupp, Florian and Seufert, Jens and Mies, Jan and Damme, Alexander and Dellermann, Theresa and Hammond, Kai and Kupfer, Thomas and Radacki, Krzysztof and Thiess, Torsten and Braunschweig, Holger}, title = {Stable Lewis Base Adducts of Tetrahalodiboranes: Synthetic Methods and Structural Diversity}, series = {Chemistry - A European Journal}, journal = {Chemistry - A European Journal}, doi = {10.1002/chem.201901437}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-184888}, year = {2019}, abstract = {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.}, language = {en} } @article{DietzArrowsmithReichletal.2022, author = {Dietz, Maximilian and Arrowsmith, Merle and Reichl, Stephan and Lugo-Fuentes, Leonardo I. and Jim{\´e}nez-Halla, J. Oscar C. and Scheer, Manfred and Braunschweig, Holger}, title = {Stable Two-Legged Parent Piano-Stool and Mixed Diborabenzene-E\(_{4}\) (E=P, As) Sandwich Complexes of Group 8}, series = {Angewandte Chemie International Edition}, volume = {61}, journal = {Angewandte Chemie International Edition}, number = {36}, doi = {10.1002/anie.202206840}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-293880}, year = {2022}, abstract = {A cyclic alkyl(amino)carbene-stabilized 1,4-diborabenzene (DBB) ligand enables the isolation of 18-electron two-legged parent piano-stool Fe\(^{0}\) and Ru\(^{0}\) complexes, [(η\(^{6}\)-DBB)M(CO)\(_{2}\)], the ruthenium complex being the first of its kind to be structurally characterized. [(η\(^{6}\)-DBB)Fe(CO)\(_{2}\)] reacts with E\(_{4}\) (E=P, As) to yield mixed DBB-cyclo-E\(_{4}\) sandwich complexes with planar E\(_{4}\)\(^{2-}\) ligands. Computational analyses confirm the strong electron-donating capacity of the DBB ligand and show that the E\(_{4}\) ligand is bound by four equivalent Fe-P σ bonds.}, 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{CuiDietzHaerterichetal.2021, author = {Cui, Jingjing and Dietz, Maximilian and H{\"a}rterich, Marcel and Fantuzzi, Felipe and Lu, Wei and Dewhurst, Rian D. and Braunschweig, Holger}, title = {Diphosphino-Functionalized 1,8-Naphthyridines: a Multifaceted Ligand Platform for Boranes and Diboranes}, series = {Chemistry—A European Journal}, volume = {27}, journal = {Chemistry—A European Journal}, number = {63}, doi = {10.1002/chem.202102721}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256994}, pages = {15751-15756}, year = {2021}, abstract = {A 1,8-naphthyridine diphosphine (NDP) reacts with boron-containing Lewis acids to generate complexes featuring a number of different naphthyridine bonding modes. When exposed to diborane B\(_{2}\)Br\(_{4}\), NDP underwent self-deprotonation to afford [NDP-B\(_{2}\)Br\(_{3}\)]Br, an unsymmetrical diborane comprised of four fused rings. The reaction of two equivalents of monoborane BBr\(_{3}\) and NDP in a non-polar solvent provided the simple phosphine-borane adduct [NDP(BBr\(_{3}\))\(_{2}\)], which then underwent intramolecular halide abstraction to furnish the salt [NDP-BBr\(_{2}\)][BBr\(_{4}\)], featuring a different coordination mode from that of [NDP-B\(_{2}\)Br\(_{3}\)]Br. Direct deprotonation of NDP by KHMDS or PhCH2K generates mono- and dipotassium reagents, respectively. The monopotassium reagent reacts with one or half an equivalent of B\(_{2}\)(NMe\(_{2}\))\(_{2}\)Cl\(_{2}\) to afford NDP-based diboranes with three or four amino substituents.}, 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} } @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{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} } @article{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 diborenes and their 90°-twisted diradical congeners}, series = {Nature Communications}, volume = {9}, journal = {Nature Communications}, number = {Article number: 1197}, doi = {10.1038/s41467-018-02998-3}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-160431}, 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} } @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{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} }