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Zusammenfassung:
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.
