@article{64005,
  abstract     = {{A novel immobilized chiral dirhodium catalyst, Rh2(S-PTTL)3(S-PTTL-linker)∼SBA-15 (8), has been prepared via click reaction of azide-groups on functionalized SBA-15 with the dirhodium complex Rh2(S-PTTL)3(S-PTTL-alkyne) (6) containing an alkyne moiety. During the synthesis of this complex, one chiral ligand of the parent Rh2(S-PTTL)4 catalyst is exchanged with an analogous chiral ligand system containing an alkyne moiety, which to a great extent maintains the intrinsic catalytic performance of the catalyst. The heterogeneous dirhodium catalyst is characterized by FT-IR and 13C solid-state NMR to validate the successful immobilization. The catalytic performance of the heterogeneous catalyst 8 is investigated in the asymmetric cyclopropanation of 3-diazooxindole with different aryl alkenes that form spiro-cyclopropyloxindoles which serve as precursors for pharmaceuticals. The resulting heterogeneous catalyst shows high catalytic activity and significant enantioselectivity. Importantly, it can be readily recovered and reused at least four times without significant loss of its catalytic performance.}},
  author       = {{Li, Zhenzhong and Rösler, Lorenz and Wissel, Till and Breitzke, Hergen and Gutmann, Torsten and Buntkowsky, Gerd}},
  journal      = {{Journal of CO2 Utilization}},
  keywords     = {{immobilized catalyst, asymmetric cyclopropanation, Chiral dirhodium}},
  pages        = {{101682}},
  title        = {{{Immobilization of a chiral dirhodium catalyst on SBA-15 via click-chemistry: Application in the asymmetric cyclopropanation of 3-diazooxindole with aryl alkenes}}},
  doi          = {{10.1016/j.jcou.2021.101682}},
  volume       = {{52}},
  year         = {{2021}},
}

@article{63956,
  abstract     = {{The synthesis of novel robust and stable iridium-based immobilized catalysts on silica-polymer hybrid materials (Si-PB-Ir) is described. These catalysts are characterized by a combination of 1D P-31 CP-MAS and 2D P-31-H-1 HETCOR and J-resolved multinuclear solid state NMR experiments. Different binding situations such as singly and multiply coordinated phosphines are identified. Density functional theory (DFT) calculations are performed to corroborate the interpretation of the experimental NMR data, in order to propose a structural model of the heterogenized catalysts. Finally, the catalytic activity of the Si-PB-Ir catalysts is investigated for the hydrogenation of styrene employing para-enriched hydrogen gas.}},
  author       = {{Gutmann, Torsten and Alkhagani, S. and Rothermel, N. and Limbach, H. H. and Breitzke, H. and Buntkowsky, G.}},
  issn         = {{0942-9352}},
  journal      = {{Zeitschrift Fur Physikalische Chemie-International Journal of Research in Physical Chemistry & Chemical Physics}},
  keywords     = {{Chemistry, dynamic nuclear-polarization, solid-state nmr, DFT, heterogeneous catalysis, hydrido complexes, hydrogenation, immobilized catalyst, inorganic hybrid, iridium, materials, mesoporous, molecular-orbital methods, PHIP, phosphine complexes, reusable catalysts, silica, solid-state-NMR, wilkinsons catalyst}},
  number       = {{3}},
  pages        = {{653–669}},
  title        = {{{P-31-Solid-State NMR Characterization and Catalytic Hydrogenation Tests of Novel heterogenized Iridium-Catalysts}}},
  doi          = {{10.1515/zpch-2016-0837}},
  volume       = {{231}},
  year         = {{2017}},
}

@article{63963,
  abstract     = {{A novel heterogeneous dirhodium catalyst has been synthesized. This stable catalyst is constructed from dirhodium acetate dimer (Rh2(OAc)4) units, which are covalently linked to amine- and carboxyl-bifunctionalized mesoporous silica (SBA-15NH2COOH). It shows good efficiency in catalyzing the cyclopropanation reaction of styrene and ethyl diazoacetate (EDA) forming cis- and trans-1-ethoxycarbonyl-2-phenylcyclopropane. To characterize the structure of this catalyst and to confirm the successful immobilization, heteronuclear solid-state NMR experiments have been performed. The high application potential of dynamic nuclear polarization (DNP) NMR for the analysis of binding sites in this novel catalyst is demonstrated. Signal-enhanced 13C CP MAS and 15N CP MAS techniques have been employed to detect different carboxyl and amine binding sites in natural abundance on a fast time scale. The interpretation of the experimental chemical shift values for different binding sites has been corroborated by quantum chemical calculations on dirhodium model complexes.}},
  author       = {{Gutmann, Torsten and Liu, Jiquan and Rothermel, Niels and Xu, Yeping and Jaumann, Eva and Werner, Mayke and Breitzke, Hergen and Sigurdsson, Snorri T. and Buntkowsky, Gerd}},
  journal      = {{Chemistry A European Journal}},
  keywords     = {{heterogeneous catalysis, immobilized catalyst, dynamic nuclear polarization, hyperpolarization, NMR spectroscopy}},
  number       = {{9}},
  pages        = {{3798–3805}},
  publisher    = {{WILEY-VCH Verlag}},
  title        = {{{Natural Abundance 15N NMR by Dynamic Nuclear Polarization: Fast Analysis of Binding Sites of a Novel Amine-Carboxyl-Linked Immobilized Dirhodium Catalyst}}},
  doi          = {{10.1002/chem.201405043}},
  volume       = {{21}},
  year         = {{2015}},
}