@article{OberdorfHanftRamleretal.2021, author = {Oberdorf, Kai and Hanft, Anna and Ramler, Jacqueline and Krummenacher, Ivo and Bickelhaupt, Matthias and Poater, Jordi and Lichtenberg, Crispin}, title = {Bismuth Amides Mediate Facile and Highly Selective Pn-Pn Radical-Coupling Reactions (Pn=N, P, As)}, series = {Angewandte Chemie, International Edition}, volume = {60}, journal = {Angewandte Chemie, International Edition}, number = {12}, doi = {10.1002/anie.202015514}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236582}, pages = {6441-6445}, year = {2021}, abstract = {The controlled release of well-defined radical species under mild conditions for subsequent use in selective reactions is an important and challenging task in synthetic chemistry. We show here that simple bismuth amide species [Bi(NAr\(_2\))\(_3\)] readily release aminyl radicals [NAr\(_2\)]. at ambient temperature in solution. These reactions yield the corresponding hydrazines, Ar\(_2\)N-NAr\(_2\), as a result of highly selective N-N coupling. The exploitation of facile homolytic Bi-Pn bond cleavage for Pn-Pn bond formation was extended to higher homologues of the pnictogens (Pn=N-As): homoleptic bismuth amides mediate the highly selective dehydrocoupling of HPnR\(_2\) to give R\(_2\)Pn-PnR\(_2\). Analyses by NMR and EPR spectroscopy, single-crystal X-ray diffraction, and DFT calculations reveal low Bi-N homolytic bond-dissociation energies, suggest radical coupling in the coordination sphere of bismuth, and reveal electronic and steric parameters as effective tools to control these reactions.}, language = {en} } @unpublished{BraunschweigKrummenacherLichtenbergetal.2016, author = {Braunschweig, Holger and Krummenacher, Ivo and Lichtenberg, Crispin and Mattock, James and Sch{\"a}fer, Marius and Schmidt, Uwe and Schneider, Christoph and Steffenhagen, Thomas and Ullrich, Stefan and Vargas, Alfredo}, title = {Dibora[2]ferrocenophane: A Carbene-Stabilized Diborene in a Strained cis-Configuration}, series = {Angewandte Chemie, International Edition}, journal = {Angewandte Chemie, International Edition}, doi = {10.1002/anie.201609601}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-141981}, pages = {9}, year = {2016}, abstract = {Unsaturated bridges that link the two cyclopentadienyl ligands together in strained ansa metallocenes are rare and limited to carbon-carbon double bonds. The synthesis and isolation of a strained ferrocenophane containing an unsaturated two-boron bridge, isoelectronic with a C=C double bond, was achieved by reduction of a carbene-stabilized 1,1'-bis(dihaloboryl)ferrocene. A combination of spectroscopic and electrochemical measurements as well as density functional theory (DFT) calculations was used to assess the influence of the unprecedented strained cis configuration on the optical and electrochemical properties of the carbene-stabilized diborene unit. Initial reactivity studies show that the dibora[2]ferrocenophane is prone to boron-boron double bond cleavage reactions.}, subject = {Metallocene}, language = {en} } @article{MukhopadhyaySchleierWirsingetal.2020, author = {Mukhopadhyay, Deb Pratim and Schleier, Domenik and Wirsing, Sara and Ramler, Jaqueline and Kaiser, Dustin and Reusch, Engelbert and Hemberger, Patrick and Preitschopf, Tobias and Krummenacher, Ivo and Engels, Bernd and Fischer, Ingo and Lichtenberg, Crispin}, title = {Methylbismuth: an organometallic bismuthinidene biradical}, series = {Chemical Science}, volume = {11}, journal = {Chemical Science}, number = {29}, doi = {10.1039/D0SC02410D}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-251657}, pages = {7562-7568}, year = {2020}, abstract = {We report the generation, spectroscopic characterization, and computational analysis of the first free (non-stabilized) organometallic bismuthinidene, BiMe. The title compound was generated in situ from BiMe\(_3\) by controlled homolytic Bi-C bond cleavage in the gas phase. Its electronic structure was characterized by a combination of photoion mass-selected threshold photoelectron spectroscopy and DFT as well as multi-reference computations. A triplet ground state was identified and an ionization energy (IE) of 7.88 eV was experimentally determined. Methyl abstraction from BiMe\(_3\) to give [BiMe(_2\)]• is a key step in the generation of BiMe. We reaveal a bond dissociation energy of 210 ± 7 kJ mol\(^{-1}\), which is substantially higher than the previously accepted value. Nevertheless, the homolytic cleavage of Me-BiMe\(_2\) bonds could be achieved at moderate temperatures (60-120 °C) in the condensed phase, suggesting that [BiMe\(_2\)]• and BiMe are accessible as reactive intermediates under these conditions.}, subject = {Photoelektronenspektroskopie}, language = {en} } @article{RamlerKrummenacherLichtenberg2020, author = {Ramler, Jacqueline and Krummenacher, Ivo and Lichtenberg, Crispin}, title = {Well-Defined, Molecular Bismuth Compounds: Catalysts in Photochemically Induced Radical Dehydrocoupling Reactions}, series = {Chemistry - A European Journal}, volume = {26}, journal = {Chemistry - A European Journal}, number = {64}, doi = {10.1002/chem.202002219}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224577}, pages = {14551 -- 14555}, year = {2020}, abstract = {A series of diorgano(bismuth)chalcogenides, [Bi(di-aryl)EPh], has been synthesised and fully characterised (E=S, Se, Te). These molecular bismuth complexes have been exploited in homogeneous photochemically-induced radical catalysis, using the coupling of silanes with TEMPO as a model reaction (TEMPO=(tetramethyl-piperidin-1-yl)-oxyl). Their catalytic properties are complementary or superior to those of known catalysts for these coupling reactions. Catalytically competent intermediates of the reaction have been identified. Applied analytical techniques include NMR, UV/Vis, and EPR spectroscopy, mass spectrometry, single-crystal X-ray diffraction analysis, and (TD)-DFT calculations.}, language = {en} }