TY  - JOUR
A1  - Braunschweig, Holger
A1  - Arnold, Thomas
A1  - Gruss, Katrin
T1  - cyclo-Tri-mu-oxido-tris{[(eta 5,eta 5)-1,2-bis(cyclopentadienyl)-1,1,2,2-tetramethyldisilane]zirconium(IV)}: atrimeric disila-bridged oxidozirconocene
N2  - no abstract available
KW  - Chemie
KW  - single-crystal X-ray study
KW  - T = 174 K
KW  - R factor = 0.027
KW  - wR factor = 0.069
KW  - data-to-parameter ratio = 23.6.
Y1  - 2011
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-74737
ER  - 
TY  - JOUR
A1  - Braunschweig, Holger
A1  - Dewhurst, Rian D.
A1  - Schwab, Katrin
A1  - Wagner, Katharina
T1  - {N ',N ''-Bis[2,6-bis(1-methylethyl)phenyl]-N,N-dimethylguanidinato-kappa N-2 ',N ''}dibromidoborane
N2  - In the molecular structure of the title compound, C27H40N3BBr2, the B atom is connected to two bromide substituents and a guanidinate scaffold, forming a four– membered ring. An aryl group is connected to each N atom in the ring that contains two isopropyl groups in positions 2 and 6.
KW  - Anorganische Chemie
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-67622
ER  - 
TY  - JOUR
A1  - Braunschweig, Holger
A1  - Damme, Alexander
T1  - 1,2-Bis(dimethylamino)-1,2-bis(2,4,6-triisopropylphenyl)diborane(4)
N2  - In the molecular structure of the title compound, C34H58B2N2, each B atom of the diborane(4) is connected to one dimethylamino group and one Tip ligand (Tip = 2,4,6-triisopropylphenyl). These findings indicate that the increased steric demand of the Tip groups exerts influence solely on the B—B separation but not on the overall geometry of the title compound.
KW  - Anorganische Chemie
Y1  - 2010
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-67639
ER  - 
TY  - JOUR
A1  - Ewing, William C.
A1  - Dellermann, Theresa
A1  - Angel Wong, Y. T.
A1  - Mattock, James D.
A1  - Vargas, Alfredo
A1  - Bryce, David L.
A1  - Dewhurst, Rian D.
A1  - Braunschweig, Holger
T1  - \(\pi\)‐Complexes of Diborynes with Main Group Atoms
JF  - Chemistry – An Asian Journal
N2  - We present herein an in‐depth study of complexes in which a molecule containing a boron‐boron triple bond is bound to tellurate cations. The analysis allows the description of these salts as true π complexes between the B−B triple bond and the tellurium center. These complexes thus extend the well‐known Dewar‐Chatt‐Duncanson model of bonding to compounds made up solely of p block elements. Structural, spectroscopic and computational evidence is offered to argue that a set of recently reported heterocycles consisting of phenyltellurium cations complexed to diborynes bear all the hallmarks of \(\pi\)‐complexes in the \(\pi\)‐complex/metallacycle continuum envisioned by Joseph Chatt. Described as such, these compounds are unique in representing the extreme of a metal‐free continuum with conventional unsaturated three‐membered rings (cyclopropenes, azirenes, borirenes) occupying the opposite end.
KW  - boron
KW  - main group elements
KW  - solid-state NMR
KW  - \(\pi\) interactions
KW  - multiple bonds
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214677
VL  - 15
IS  - 10
SP  - 1553
EP  - 1557
ER  - 
TY  - JOUR
A1  - Thiess, Torsten
A1  - Ernst, Moritz
A1  - Kupfer, Thomas
A1  - Braunschweig, Holger
T1  - Facile Access to Substituted 1,4‐Diaza‐2,3‐Diborinines
JF  - Chemistry – A European Journal
N2  - Several bis(dimethylamino)‐substituted 1,4‐diaza‐2,3‐diborinines (DADBs) were synthesized with variable substituents at the backbone nitrogen atoms. By reaction with HCl or BX\(_{3}\) (X=Br, I), these species were successfully converted into their synthetically more useful halide congeners. The high versatility of the generated B−X bonds in further functionalization reactions at the boron centers was demonstrated by means of salt elimination (MeLi) and commutation (NMe\(_{2}\) DADBs) reactions, thus making the DADB system a general structural motif in diborane(4) chemistry. A total of 18 DADB derivatives were characterized in the solid state by X‐ray diffraction, revealing a strong dependence of the heterocyclic bonding parameters from the exocyclic substitution pattern at boron. According to our experiments towards the realization of a Dipp‐substituted, sterically encumbered DADB, the mechanism of DADB formation proceeds via a transient four‐membered azadiboretidine intermediate that subsequently undergoes ring expansion to afford the six‐membered DADB heterocycle.
KW  - azadiboretidines
KW  - B,N-heterocycles
KW  - diazadiborinines
KW  - diboranes
KW  - ring expansion
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-214650
VL  - 26
IS  - 13
SP  - 2967
EP  - 2972
ER  - 
TY  - JOUR
A1  - Gerlach, Marius
A1  - Monninger, Sophie
A1  - Schleier, Domenik
A1  - Hemberger, Patrick
A1  - Goettel, James T.
A1  - Braunschweig, Holger
A1  - Fischer, Ingo
T1  - Photoelectron Photoion Coincidence Spectroscopy of NCl\(_{3}\) and NCl\(_{2}\)
JF  - ChemPhysChem
N2  - We investigate NCl\(_{3}\) and the NCl\(_{2}\) radical by photoelectron-photoion coincidence spectroscopy using synchrotron radiation. The mass selected threshold photoelectron spectrum (ms-TPES) of NCl\(_{3}\) is broad and unstructured due to the large geometry change. An ionization energy of 9.7±0.1 eV is estimated from the spectrum and supported by computations. NCl2 is generated by photolysis at 213 nm from NCl\(_{3}\) and its ms-TPES shows an extended vibrational progression with a 90 meV spacing that is assigned to the symmetric N−Cl stretching mode in the cation. An adiabatic ionization energy of 9.94 ± 0.02 eV is determined.
KW  - radicals
KW  - photoelectron spectroscopy
KW  - synchrotron radiation
KW  - nitrogen trichloride
KW  - photolysis
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-257322
VL  - 22
IS  - 21
ER  - 
TY  - JOUR
A1  - Full, Felix
A1  - Wölflick, Quentin
A1  - Radacki, Krzysztof
A1  - Braunschweig, Holger
A1  - Nowak‐Król, Agnieszka
T1  - Enhanced Optical Properties of Azaborole Helicenes by Lateral and Helical Extension
JF  - Chemistry – A European Journal
N2  - The synthesis and characterization of laterally extended azabora[5]‐, ‐[6]‐ and ‐[7]helicenes, assembled from N‐heteroaromatic and dibenzo[g,p]chrysene building blocks is described. Formally, the π‐conjugated systems of the pristine azaborole helicenes were enlarged with a phenanthrene unit leading to compounds with large Stokes shifts, significantly enhanced luminescence quantum yields (Φ) and dissymmetry factors (g\(_{lum}\)). The beneficial effect on optical properties was also observed for helical elongation. The combined contributions of lateral and helical extensions resulted in a compound showing green emission with Φ of 0.31 and |g\(_{lum}\)| of 2.2×10\(^{−3}\), highest within the series of π‐extended azaborahelicenes and superior to emission intensity and chiroptical response of its non‐extended congener. This study shows that helical and lateral extensions of π‐conjugated systems are viable strategies to improve features of azaborole helicenes. In addition, single crystal X‐ray analysis of configurationally stable [6]‐ and ‐[7]helicenes was used to provide insight into their packing arrangements.
KW  - azaborole
KW  - circularly polarized luminescence
KW  - fluorescence
KW  - helicene
KW  - π-extension
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-293671
VL  - 28
IS  - 62
ER  - 
TY  - JOUR
A1  - Weiser, Jonas
A1  - Cui, Jingjing
A1  - Dewhurst, Rian D.
A1  - Braunschweig, Holger
A1  - Engels, Bernd
A1  - Fantuzzi, Felipe
T1  - Structure and bonding of proximity‐enforced main‐group dimers stabilized by a rigid naphthyridine diimine ligand
JF  - Journal of Computational Chemistry
N2  - The development of ligands capable of effectively stabilizing highly reactive main‐group species has led to the experimental realization of a variety of systems with fascinating properties. In this work, we computationally investigate the electronic, structural, energetic, and bonding features of proximity‐enforced group 13–15 homodimers stabilized by a rigid expanded pincer ligand based on the 1,8‐naphthyridine (napy) core. We show that the redox‐active naphthyridine diimine (NDI) ligand enables a wide variety of structural motifs and element‐element interaction modes, the latter ranging from isolated, element‐centered lone pairs (e.g., E = Si, Ge) to cases where through‐space π bonds (E = Pb), element‐element multiple bonds (E = P, As) and biradical ground states (E = N) are observed. Our results hint at the feasibility of NDI‐E2 species as viable synthetic targets, highlighting the versatility and potential applications of napy‐based ligands in main‐group chemistry.
KW  - bond theory
KW  - computational chemistry
KW  - density functional calculations
KW  - main group elements
KW  - N ligands
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312586
VL  - 44
IS  - 3
SP  - 456
EP  - 467
ER  - 
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  - Witte, Robert
A1  - Arrowsmith, Merle
A1  - Lamprecht, Anna
A1  - Schorr, Fabian
A1  - Krummenacher, Ivo
A1  - Braunschweig, Holger
T1  - C−C and C−N Bond Activation, Lewis‐Base Coordination and One‐ and Two‐Electron Oxidation at a Linear Aminoborylene
JF  - Chemistry – A European Journal
N2  - A cyclic alkyl(amino)carbene (CAAC)‐stabilized dicoordinate aminoborylene is synthesized by the twofold reduction of a [(CAAC)BCl\(_{2}\)(TMP)] (TMP=2,6‐tetramethylpiperidyl) precursor. NMR‐spectroscopic, X‐ray crystallographic and computational analyses confirm the cumulenic nature of the central C=B=N moiety. Irradiation of [(CAAC)B(TMP)] (2) resulted in an intramolecular C−C bond activation, leading to a doubly‐fused C\(_{10}\)BN heterocycle, while the reaction with acetonitrile resulted in an aryl migration from the CAAC to the acetonitrile nitrogen atom, concomitant with tautomerization of the latter to a boron‐bound allylamino ligand. One‐electron oxidation of 2 with CuX (X=Cl, Br) afforded the corresponding amino(halo)boryl radicals, which were characterized by EPR spectroscopy and DFT calculations. Placing 2 under an atmosphere of CO afforded the tricoordinate (CAAC,CO)‐stabilized aminoborylene. Finally, the twofold oxidation of 2 with chalcogens led, in the case of N\(_{2}\)O and sulfur, to the splitting of the B−C\(_{CAAC}\) bond and formation of the 2,4‐diamino‐1,3,2,4‐dichalcogenadiboretanes and CAAC‐chalcogen adducts, whereas with selenium a monomeric boraselenone was isolated, which showed some degree of B−Se multiple bonding.
KW  - bond activation
KW  - boraselenone
KW  - dicoordinate borylene
KW  - one-electron oxidation
KW  - push-pull stabilization
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-312491
VL  - 29
IS  - 16
ER  -