Browsing by Author "Schubert, Hartmut"

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    Leveraging N-exo substituents to tune the donor/acceptor properties of mesoionic imines (MIIs)
    (2024) Rudolf, Richard; Todorovski, Andrej; Schubert, Hartmut; Sarkar, Biprajit
    In this work, we show two synthetic routes to substitute the Nexo position of mesoionic imines (MIIs). By Buchwald-Hartwig amination, 5-amino-1,2,3-triazoles can be arylated at the said position, showing the versatility of amino-triazoles as building blocks for MIIs. The reaction of MIIs with electrophiles (MeI, fluoro-arenes) highlights the nucleophilic nature of MIIs as even at room temperature aromatic C-F bonds can be activated with MIIs. By combining experimental methods such as Tolman/Huynh-electronic-parameter and crystallographic interpretations with theoretical calculations, we establish that MIIs expand the nucleophilicity scale of N-donors. Contrary to the flanking substituents on the triazole scaffold, the Nexo substituent heavily influences the donating ability of MIIs: electron-withdrawing substituents will dramatically decrease the donor strength of the MII ligand. We have now established ways to functionalise not only the triazole backbone but also the Nexo position. More importantly, we show here how the substitution pattern influences the electronic structure of MIIs. Such electronic tunability should make MIIs suitable for use in various fields of chemistry.
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    Synthesis of cobalt‐tin and ‐lead tetrylidynes : reactivity study of the triple bond
    (2023) Auer, Maximilian; Zwettler, Kathrin; Eichele, Klaus; Schubert, Hartmut; Sindlinger, Christian P.; Wesemann, Lars
    Tetrylidynes [TbbSn≡Co(PMe3)3] (1 a) and [TbbPb≡Co(PMe3)3] (2) (Tbb=2,6-[CH(SiMe3)2]2-4-(t-Bu)C6H2) are accessed for the first time via a substitution reaction between [Na(OEt2)][Co(PMe3)4] and [Li(thf)2][TbbEBr2] (E=Sn, Pb). Following an alternative procedure the stannylidyne [Ar*Sn≡Co(PMe3)3] (1 b) was synthesized by hydrogen atom abstraction using AIBN from the paramagnetic hydride complex [Ar*SnH=Co(PMe3)3] (4) (AIBN=azobis(isobutyronitrile)). The stannylidyne 1 a adds two equivalents of water to yield the dihydroxide [TbbSn(OH)2CoH2(PMe3)3] (5). In reaction of the stannylidyne 1 a with CO2 a product of a redox reaction [TbbSn(CO3)Co(CO)(PMe3)3] (6) was isolated. Protonation of the tetrylidynes occurs at the cobalt atom to give the metalla-stanna vinyl cation [TbbSn=CoH(PMe3)3][BArF4] (7 a) [ArF=C6H3-3,5-(CF3)2]. The analogous germanium and tin cations [Ar*E=CoH(PMe3)3][BArF4] (E=Ge 9, Sn 7 b) (Ar*=C6H3(2,6-Trip)2, Trip=2,4,6-C6H2iPr3) were also obtained by oxidation of the paramagnetic complexes [Ar*EH=Co(PMe3)3] (E=Ge 3, Sn 4), which were synthesized by substitution of a PMe3 ligand of [Co(PMe3)4] by a hydridoylene (Ar*EH) unit.