@unpublished{StennettMattockVollertetal.2018,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@unpublished{StennettMattockPentecostetal.2018,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}
}
@article{StennettJayaramanBrueckneretal.2020,
  author    = {Stennett, Tom E. and Jayaraman, Arumugam and Br{\"u}ckner, Tobias and Schneider, Lea and Braunschweig, Holger},
  title     = {Hydrophosphination of boron-boron multiple bonds},
  series = {Chemical Science},
  volume    = {11},
  journal   = {Chemical Science},
  doi       = {10.1039/c9sc05908c},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240681},
  pages     = {1335-1341},
  year      = {2020},
  abstract  = {Five compounds containing boron-boron multiple bonds are shown to undergo hydrophosphination reactions with diphenylphosphine in the absence of a catalyst. With diborenes, the products obtained are highly dependent on the substitution pattern at the boron atoms, with both 1,1- and 1,2- hydrophosphinations observed. With a symmetrical diboryne, 1,2-hydrophosphination yields a hydro(phosphino)diborene. The different mechanistic pathways for the hydrophosphination of diborenes are rationalised with the aid of density functional theory calculations.},
  language  = {en}
}
@unpublished{StennettBissingerGriesbecketal.2019,
  author    = {Stennett, Tom E. and Bissinger, Philipp and Griesbeck, Stefanie and Ullrich, Stefan and Krummenacher, Ivo and Auth, Michael and Sperlich, Andreas and Stolte, Matthias and Radacki, Krzysztof and Yao, Chang-Jiang and W{\"u}rthner, Frank and Steffen, Andreas and Marder, Todd B. and Braunschweig, Holger},
  title     = {Near-Infrared Quadrupolar Chromophores Combining Three-Coordinate Boron-Based Superdonor and Superacceptor Units},
  series = {Angewandte Chemie, International Edition},
  journal   = {Angewandte Chemie, International Edition},
  doi       = {10.1002/anie.201900889},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-180391},
  year      = {2019},
  abstract  = {In this work, two new quadrupolar A-π-D-π-A chromophores have been prepared featuring a strongly electron- donating diborene core and strongly electron-accepting dimesitylboryl F(BMes2) and bis(2,4,6-tris(trifluoromethyl)phenyl)boryl (BMes2) end groups. Analysis of the compounds by NMR spectroscopy, X-ray crystallography, cyclic voltammetry and UV-vis-NIR absorption and emission spectroscopy indicated that the compounds possess extended conjugated π-systems spanning their B4C8 cores. The combination of exceptionally potent π-donor (diborene) and π- acceptor (diarylboryl) groups, both based on trigonal boron, leads to very small HOMO-LUMO gaps, resulting in strong absorption in the near-IR region with maxima in THF at 840 and 1092 nm, respectively, and very high extinction coefficients of ca. 120,000 M-1cm-1. Both molecules also display weak near-IR fluorescence with small Stokes shifts.},
  language  = {en}
}
@unpublished{StennettBertermannBraunschweig2018,
  author    = {Stennett, Tom and Bertermann, R{\"u}diger and Braunschweig, Holger},
  title     = {Construction of Linear and Branched Tetraboranes via 1,1- and 1,2-Diboration of Diborenes},
  series = {Angewandte Chemie, International Edition},
  journal   = {Angewandte Chemie, International Edition},
  doi       = {10.1002/anie.201809976},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-178276},
  year      = {2018},
  abstract  = {Sterically unencumbered diborenes based on a benzylphosphine chelate undergo diboration reactions with bis(catecholato)diboron in the absence of a catalyst to yield tetraboranes. The symmetrical diborenes studied undergo 1,2- diborations, whereas an unsymmetrical derivative was found to yield a triborylborane-phosphine adduct as the result of a formal 1,1-diboration. A related borylborylene compound also underwent a 1,2-diboration to produce a borylene-borane adduct.},
  language  = {en}
}
@article{LindlGuoKrummenacheretal.2021,
  author    = {Lindl, Felix and Guo, Xueying and Krummenacher, Ivo and Rauch, Florian and Rempel, Anna and Paprocki, Valerie and Dellermann, Theresa and Stennett, Tom E. and Lamprecht, Anna and Br{\"u}ckner, Tobias and Radacki, Krzysztof and B{\´e}langer-Chabot, Guillaume and Marder, Todd B. and Lin, Zhenyang and Braunschweig, Holger},
  title     = {Rethinking Borole Cycloaddition Reactivity},
  series = {Chemistry—A European Journal},
  volume    = {27},
  journal   = {Chemistry—A European Journal},
  number    = {43},
  doi       = {10.1002/chem.202101290},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256888},
  pages     = {11226-11233},
  year      = {2021},
  abstract  = {Boroles are attracting broad interest for their myriad and diverse applications, including in synthesis, small molecule activation and functional materials. Their properties and reactivity are closely linked to the cyclic conjugated diene system, which has been shown to participate in cycloaddition reactions, such as the Diels-Alder reaction with alkynes. The reaction steps leading to boranorbornadienes, borepins and tricyclic boracyclohexenes from the thermal reaction of boroles with alkynes are seemingly well understood as judged from the literature. Herein, we question the long-established mechanistic picture of pericyclic rearrangements by demonstrating that seven-membered borepins (i. e., heptaphenylborepin and two derivatives substituted with a thienyl and chloride substituent on boron) exist in a dynamic equilibrium with the corresponding bicyclic boranorbornadienes, the direct Diels-Alder products, but are not isolable products from the reactions. Heating gradually converts the isomeric mixtures into fluorescent tricyclic boracyclohexenes, the most stable isomers in the series. Results from mechanistic DFT calculations reveal that the tricyclic compounds derive from the boranorbornadienes and not the borepins, which were previously believed to be intermediates in purely pericyclic processes.},
  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{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}
}
@article{BruecknerHessStennettetal.2021,
  author    = {Br{\"u}ckner, Tobias and Heß, Merlin and Stennett, Tom E. and Rempel, Anna and Braunschweig, Holger},
  title     = {Synthesis of Boron Analogues of Enamines via Hydroamination of a Boron-Boron Triple Bond},
  series = {Angewandte Chemie, International Edition},
  volume    = {60},
  journal   = {Angewandte Chemie, International Edition},
  number    = {2},
  doi       = {10.1002/anie.202012101},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-240669},
  pages     = {736-741},
  year      = {2021},
  abstract  = {An N-heterocyclic-carbene-stabilized diboryne undergoes rapid, high-yielding and catalyst-free hydroamina- tion reactions with primary amines, yielding 1-amino-2-hydro- diborenes, which can be considered boron analogues of enamines. The electronics of the organic substituent at nitrogen influence the structure and further reactivity of the diborene product. With electron-rich anilines, a second hydroamination can occur at the diborene to generate 1,1-diamino-2,2-dihy- drodiboranes. With isopropylamine, the electronic influence of the alkyl substituent upon the diborene leads to an unprece- dented boron-mediated intramolecular N-dearylation reaction of an N-heterocyclic carbene unit.},
  language  = {en}
}
@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}
}