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Université de Fribourg

Catalytically active palladium pyridylidene complexes : pyridinium ionic liquids as N-heterocyclic carbene precursors

Albrecht, Martin ; Stoeckli-Evans, Helen

In: Chemical Communications, 2005, no. 37, p. 4705-4707

Pyridinium salts similar to those used as ionic liquid solvents readily undergo palladation in the presence of a base, thus giving palladium-pyridylidene N-heterocyclic carbene complexes that are active catalysts for Suzuki-type cross-coupling reactions.

Université de Fribourg

Stereoselectivity in the formation of tris-diimine complexes of Fe(II), Ru(II), and Os(II) with a C₂-symmetric chiral derivative of 2,2′-bipyridine

Drahoňovský, Dušan ; Knof, Ulrich ; Jungo, Laurence ; Belser, Thomas ; Neels, Antonia ; Labat, Gaël Charles ; Stoeckli-Evans, Helen ; Zelewsky, Alexander von

In: Dalton Transactions, 2006, p. 1444 - 1454

A C₂-symmetric enantiopure 4,5-bis(pinene)-2,2′-bipyridine ligand (–)-L was used to investigate the diastereoselectivity in the formation of [ML₃]²⁺ coordination species (M = Fe(II), Ru(II), Os(II), Zn(II), Cd(II), Cu(II), Ni(II)), and [ML₂Cl₂] (M = Ru(II), Os(II)). The X-ray structures of the [ML₃]²⁺ complexes were determined for Δ-[FeL₃](PF₆)₂,...

Université de Fribourg

Diastereoselective synthesis of coordination compounds: a chiral tripodal ligand based on bipyridine units and its ruthenium(II) and iron(II) complexes

Hamann, Christine ; Zelewsky, Alexander von ; Neels, Antonia ; Stoeckli-Evans, Helen

In: Dalton Transactions, 2004, vol. 3, p. 402-406

The enantiomerically pure chiral tris-chelating ligand (+)-(7S,10R)-L(L) comprising three 4,5-pinenobipyridine subunits connected through a mesityl spacer has been synthesized. Complexes of L with RuII and FeII have been prepared and characterised. NMR spectroscopy indicates that...

Université de Fribourg

Synthesis and structural analysis of palladium biscarbene complexes derived from bisimidazolium ligand precursors

Heckenroth, Marion ; Neels, Antonia ; Stoeckli-Evans, Helen ; Albrecht, Martin

In: Inorganica Chimica Acta, 2006, vol. 359, no. 6, p. 1929-1938

The palladation of potentially chelating bisimidazolium ligand precursors with palladium acetate gives bridging bimetallic, chelating monometallic, and homoleptic tetracarbene complexes. The coordination mode of the biscarbene ligand has been identified by spectroscopic analysis and crystallographic characterization of representative complexes, including the first example of a biscarbene A-frame...

Université de Fribourg

A perfluorocyclopentene dithienylethene based molecular switch: 1,2-bis[5-(4-ethynylphenyl)-2-methylthiophen-3-yl]-3,3,4,4,5,5-hexafluorocyclopentene

Iyer, Vijay Mahadevan ; Stoeckli-Evans, Helen ; Belser, Peter

In: Acta Crystallographica E, 2006, vol. 62, no. 9, p. o3942-o3943

The title compound, C₃₁H₁₈F₆S₂, is a molecular switch based on dithienylperfluorocyclopentene. The molecule possesses pseudo-C₂ symmetry and has the open form of the switch. There are a number of intramolecular C-H...F hydrogen bonds, but in the crystal structure there are no interactions between symmetry-related molecules.

Université de Fribourg

Crystal structures of trans-di­chlorido­tetra­kis­[1-(2,6-diiso­propyl­phen­yl)-1H-imidazole-ΚN³]iron(II), trans-di­bromido­tetra­kis­[1-(2,6-diiso­propyl­phen­yl)-1H-imidazole-ΚN³]iron(II) and trans-di­bromido­tetra­kis­[1-(2,6-diiso­propyl­phen­yl)-1H-imidazole-ΚN³]iron(II) diethyl ether disolvate

Mafua, Roger ; Jenny, Titus ; Labat, Gael ; Neels, Antonia ; Stoeckli-Evans, Helen

In: Acta Crystallographica Section E Structure Reports Online, 2014, vol. 70, no. 8, p. 72–76

The title compounds, [FeCl₂(C₁₅H₂₀N₂)₄], (I), [FeBr₂(C₁₅H₂₀N₂)₄], (II), and [FeBr₂(C₁₅H₂₀N₂)₄]·2C₄H₁₀O, (IIb), respectively, all have triclinic symmetry, with (I) and (II) being isotypic. The FeII atoms in each of the structures are located on an inversion center. They have octa­hedral FeX₂N₄ (X = Cl and Br,...

Université de Fribourg

Self-assembly of Ag(I) helicates with new enantiopure 5,6-Chiragen type ligands

Mamula, Olimpia ; Bark, Thomas ; Quinodoz, Boris ; Stoeckli-Evans, Helen ; Zelewsky, Alexvon

In: Inorganica Chimica Acta, 2018, vol. 475, p. 200–206

Two new chiral bis-bidentate, C2-symmetrical ligands belonging to the Chiragen family have been synthesised and characterised. They are designed for polynuclear self-assemblies since the two (−)-5,6-pinenebipyridines units are connected by bridges whose length and rigidity avoids the coordination of the bipyridine moieties to the same metal centre. The ligand L1 with a 1,4-dimethylene...

Université de Fribourg

Main-chain organometallic polymers comprising redox-active iron(II) centers connected by ditopic N-heterocyclic carbenes

Mercs, Laszlo ; Neels, Antonia ; Stoeckli-Evans, Helen ; Albrecht, Martin

In: Dalton Transactions, 2009, vol. 35, p. 7168-7178

Main-chain organometallic polymers were synthesized from bimetallic iron(II) complexes containing a ditopic N-heterocyclic carbene (NHC) ligand [(cp)(CO)LFe(NHC∼NHC)Fe(cp)(CO)L]X₂ (where NHC∼NHC represents a bridging dicarbene ligand, L = I⁻ or CO). Addition of a diimine ligand such as pyrazine or 4,4′-bipyridine, interconnected these bimetallic complexes and gave the...

Université de Fribourg

Probing intermetallic coupling in dinuclear N-heterocyclic carbene ruthenium(II) complexes

Mercs, Laszlo ; Neels, Antonia ; Stoeckli-Evans, Helen ; Albrecht, Martin

In: Inorganic Chemistry, 2011, vol. 50, no. 17, p. 8188–8196

A series of bimetallic N-heterocyclic carbene (NHC) ruthenium(II) complexes were synthesized, which comprise two [RuCl₂(cymene)(NHC)] units that are interlinked via the NHC nitrogens by alkyl chains of different length. Electrochemical characterization revealed two mutually dependent oxidation processes for the complex with a methylene linker, indicating moderate intramolecular electronic...