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Synthesis of ɑ-Cationic Phosphines and Their Applications as Ligands/Synthese von ɑ-Kationischer Phosphine und deren Anwendung als Liganden


Gu,  Lianghu
Research Group Alcarazo, Max-Planck-Institut für Kohlenforschung, Max Planck Society;

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Gu, L. (2016). Synthesis of ɑ-Cationic Phosphines and Their Applications as Ligands/Synthese von ɑ-Kationischer Phosphine und deren Anwendung als Liganden. PhD Thesis, Technische Universität, Dortmund.

Cite as: http://hdl.handle.net/11858/00-001M-0000-002A-F003-5
1) Bis- and Trispyrazoylborate/methane-Stabilized P(III)-Centered Cations Making use of an –onium substituent transfer strategy, we have been able to isolate and structurally characterize several P-centered polycations stabilized by bis- and tris- (pyrazoyl)borate or methane ligands. In all of these compounds, the phosphorus center adopts a pyramidal environment, which is indicative of the presence of a lone pair mainly located on this atom. However, the high positive charge at phosphorus lowers the energy of this orbital to a level that makes it unavailable for donation. The same positive charge also stabilizes quite efficiently the σ*(P-N) orbitals, thus conferring Lewis acid character to the phosphorus atom. This Lewis acidity is evident from the short contacts observed between the triflate anions and the phosphorus centers. 2) Dicationic Chelating Phosphines: Synthesis, Structure and Reactivity We outlined the preparation of new bidentate dicationic phosphines and their coordination chemistry towards different metals. Moreover, we showcased for the first time the utility of cationic ligands to promote difficult reductive elimination processes under mild condition, such as the formation of polyfluorinated biaryls from Pd(II) centers. Finally, the unique properties of these ligands in catalysis has been proven in the hydorarylation of phenyl diene with indoles and electron rich arenes. 3) Isolation and Coordination Chemistry of CAACs Substituted α-Radical Phosphines We have successfully isolated and characterized a series of CAAC (Cyclic (Alkyl)(Amino)Carbene) derived cationic phophines. Their cyclovoltammetry showed a quasi-reversible redox potential, which indicated that stable radicals were formed after one electron reduction. As a result, a series of α-radical phosphines have been synthesized and fully characterized. More intriguingly, these radical phosphines could coordinate to Au(I) and form a range of stable gold complexes that are unprecedented. In addition, we were also able to synthesize the radical phosphorus oxide. All of the synthesized radicals have been characterized by EPR and most have been crystallized. These novel compounds could be named as α-radical phosphine ligands, which might be useful in catalysis.