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Université de Fribourg

Palladium complexes containing potentially chelating pyridylidene-type carbene ligands

Poulain, Aurélie ; Neels, Antonia ; Albrecht, Martin

In: European Journal of Inorganic Chemistry, 2009, no. 13, p. 1871 - 1881

Oxidative addition of 2-bromopyridine derivatives containing a potentially chelating donor group E (E = NMe₂, SMe, SPh) to palladium(0) gives C,E-bound pyridylpalladium(II) complexes. Mono-, di-, and polymeric palladium complexes are obtained depending on the type of functionalization at the pyridyl nitrogen. With a lone pair at nitrogen, dimetallic products are isolated, while...

Université de Fribourg

Diastereoselective preparation of Cu(I) and Ag(I) double helices by the use of chiral bis-bipyridine ligands

Perret-Aebi, Laure-Emmanuelle ; Zelewsky, Alexander von ; Neels, Antonia

In: New Journal of Chemistry, 2009, vol. 33, p. 462–465

Chiral bis-5,6-pinene bipyridine type ligands have been used to form, through self-assembly reaction, dinuclear coordination compounds which show a highly diastereoselective formation of double helices with copper(I) and silver(I) as coordination centers.

Université de Fribourg

1,2,3-triazolylidenes as versatile abnormal carbene ligands for late transition metals

Mathew, Paulson ; Neels, Antonia ; Albrecht, Martin

In: Journal of the American Chemical Society, 2008, vol. 130, no. 41, p. 13534–13535

The [3 + 2] cycloaddition of azides and acetylenes followed by nitrogen quaternization was applied for the generation of novel and highly modular triazolium salts. The selective substitution of the 1,3,4-substitution pattern presets such salts as precursors for a new class of abnormal carbene ligands, thus expanding the family of these high-impact ligands. Metalation of the triazolium salts is...

Université de Fribourg

Probing the potential of N-heterocyclic carbenes in molecular electronics: redox-active metal centers interlinked by a rigid ditopic carbene ligand

Mercs, Laszlo ; Neels, Antonia ; Albrecht, Martin

In: Dalton Transactions, 2008, vol. 41, p. 5570-5576

Bimetallic homonuclear iron(II) and ruthenium(II) N-heterocyclic carbene complexes have been synthesized and crystallographically analyzed. As a spacer ligand for interconnecting the two redox-active metal centers, a ditopic carbene ligand has been used that comprises two carbene sites annelated to benzene. Detailed electrochemical and spectroelectrochemical analyses of the bimetallic...

Université de Fribourg

Palladation of diimidazolium salts at the C4 position: access to remarkably electron-rich palladium(II) centers

Heckenroth, Marion ; Kluser, Evelyne ; Neels, Antonia ; Albrecht, Martin

In: Dalton Transactions, 2008, p. 6242 - 6249

Palladation of C2-protected diimidazolium salts with Pd(OAc)₂ afforded complexes comprising C4-bound N-heterocyclic dicarbene ligands. The reactivity of these complexes towards Lewis acids (AgBF₄, AgOAc) and Brønsted acids (H₂SO₄, H₃PO₄, HOAc) revealed that abnormal C4 bonding of the carbenes markedly increases the nucleophilicity of the coordinated palladium center as compared to C2...

Université de Fribourg

Rhodium(iii) complexes containing C4-bound N-heterocyclic carbenes: synthesis, coordination chemistry, and catalytic activity in transfer hydrogenation

Yang, Liangru ; Krüger, Anneke ; Neels, Antonia ; Albrecht, Martin

In: Organometallics, 2008, vol. 27, no. 13, p. 3161–3171

Direct metalation of C2-protected diimidozolium salts with RhCl₃ or [RhCl(cod)]₂ and KI afforded a series of new rhodium(III) complexes with abnormally C4-bound, cis-chelating NHC ligands. The complexes were isolated as dimetallic species containing two (μ²-I)₃-bridged rhodium(III) centers. In the presence of coordinating ligands such as CH₃CN, PPh₃, or dppe, the dimeric...

Université de Fribourg

Piano-stool iron(ii) complexes as probes for the bonding of n-heterocyclic carbenes: indications for -acceptor ability

Mercs, Laszlo ; Labat, Gaël ; Neels, Antonia ; Ehlers, Andreas ; Albrecht, Martin

In: Organometallics, 2006, vol. 25, no. 23, p. 5648 -5656

A series of new piano-stool iron(II) complexes comprising mono- and bidentate chelating N-heterocyclic carbene ligands [Fe(cp)(CO)(NHC)(L)]X have been prepared and analyzed by spectroscopic, electrochemical, crystallographic, and theoretical methods. Selectively substituting the L site with a series of ligands going from carbene to pyridine to CO suggests that CO is the strongest π...

Université de Fribourg

Photochemistry of allenyl salicylaldehydes

Birbaum, Frédéric ; Neels, Antonia ; Bochet, Christian G.

In: Organic Letters, 2008, vol. 10, no. 15, p. 3175–3178

The intramolecular photocycloaddition of aryl aldehydes containing allene side chains is a versatile reaction as it provides a rapid and efficient access to original complex structures such as 1,3,4-tetrahydro-1,4-epoxy-5-alkylidene-2-benzoxepines 2 and substituted 2-oxa-tricyclo[5.2.2.0]1,5undeca-4,8,10-triene-9-carbaldehydes 3. Novel polycyclic structures are...

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...