Université de Fribourg

A family of immobilizable chiral bis(pinenebipyridine) ligands

Pöllnitz, Alpár ; Skupienski, Radek ; Stoeckli-Evans, Helen ; Crochet, Aurélien ; Silvestru, Anca ; Fromm, Katharina M. ; Mamula, Olimpia

In: Synlett, 2013, vol. 24, no. 19, p. 2555–2558

New enantiopure ligands containing two (–)-5,6-pinenebipyridine units connected by a bridge situated in position 6′ of the bipyridines have been prepared. The chemically addressable groups of the bridging (hydroxyl or keto) can be covalently bound to various supports in order to heterogenize the ligand.

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...

Université de Fribourg

Synthesis and tunability of abnormal 1,2,3-triazolylidene palladium and rhodium complexes

Poulain, Aurélie ; Canseco-Gonzalez, Daniel ; Hynes-Roche, Rachel ; Müller-Bunz, Helge ; Schuster, Oliver ; Stoeckli-Evans, Helen ; Neels, Antonia ; Albrecht, Martin

In: Organometallics, 2011, vol. 30, no. 5, p. 1021–1029

Palladation of N3-alkylated 1,2,3-triazolium salts with Pd(OAc)₂ afforded a μ²−I₂ bridged bimetallic complex [Pd(trz)I₂]₂ and monometallic bis(carbene) complexes Pd(trz)₂I₂ as a mixture of trans and cis isomers (trz = 1,2,3-triazol-5- ylidene). Addition of excess halide or modification of the palladation procedure from direct functionalization to a transmetalation...

Université de Fribourg

Stereoselective synthesis of cyclometalated iridium(III) complexes: characterization and photophysical properties

Yang, Liangru ; Zelewsky, Alexander von ; Nguyen, Huong P. ; Muller, Gilles ; Labat, Gaël Charles ; Stoeckli-Evans, Helen

In: Inorganica Chimica Acta, 2009, vol. 36, no. 10, p. 3853-3856

The stereoselective synthesis of a highly luminescent neutral Ir(III) complex comprising two bidentate chiral, cyclometalating phenylpyridine derivatives, and one acetylacetonate as ligands is described. The final complex and some intermediates were characterized by X-ray structural analysis, NMR-, CD-, and CPL-spectroscopy.

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

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

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

Novel HEXOL-type cyclometallated iridium(III) complexes: stereoselective synthesis and structure elucidation

Yang, Liangru ; Zelewsky, Alexander von ; Stoeckli-Evans, Helen

In: Chemical Communications, 2005, vol. (33), p. 4155

Two diastereoisomers of tetranuclear cyclometallated iridium complexes, either having an inner core of HEXOL-type [Ir(IrCl₂)₃]⁶⁺ unit and a surface of six chiral, didentate, cyclometallated ligands, are stereoselectively synthesized from an enantiopure pinenopyridine derivative.

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...