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Université de Fribourg

Organization of spin- and redox-labile metal centers into Langmuir and Langmuir–Blodgett films

Gandolfi, Claudio ; Miyashita, Naoko ; Kurth, Dirk G. ; Martinho, Paulo N. ; Morgan, Grace G. ; Albrecht, Martin

In: Dalton Transactions, 2010, vol. 39, p. 4508-4516

New sal₂(trien) ligands that contain alkoxy substituents of various length in meta position of the phenolate entities were coordinated to electronically and magnetically active iron(III) and cobalt(III) centers. The electrochemical and spectroscopic properties of these amphiphilic complexes are virtually unaffected upon alteration of the alkoxy substituents, thus providing a system...

Université de Fribourg

DFT Study of the Jahn-Teller Effect in Cu(II) Chelate Complexes

Gruden-Pavlović, Maja ; Zlatar, Matija ; Schläpfer, Carl-Wilhelm ; Daul, Claude A.

In: Journal of Molecular Structure: THEOCHEM, 2010, p. -

Density Functional Theory (DFT) in conjuction with the Intrinsic Distortion Path (IDP) is employed to study the Jahn-Teller (JT) effect in all four diastereoisomers of tris(ethylenediamine)copper(II) ([Cu(en)₃]²⁺) and tris(ethyleneglycol)copper(II) ([Cu(eg)₃]²⁺) complexes. As a consequence of the JT effect all the isomers tetragonally elongate to the C₂ configurations. Although there...

Université de Fribourg

Inducing spin crossover in amphiphilic iron(III) complexes

Martinho, Paulo N. ; Harding, Charles J. ; Müller-Bunz, Helge ; Albrecht, Martin ; Morgan, Grace G.

In: European Journal of Inorganic Chemistry, 2010, no. 5, p. 675-679

Thermal spin crossover (SCO) was induced in a high-spin FeIII complex by alkylation of the polyamino ligand backbone. The SCO profile was responsive to chain length with partial crossover observed with C₆ alkylation and full transition upon lengthening to C₁₂. No crossover was observed when the backbone was unfunctionalised, and all three complexes were obtained as unsolvated...

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

Chelating NHC ruthenium(II) complexes as robust homogeneous hydrogenation catalysts

Gandolfi, Claudio ; Heckenroth, Marion ; Neels, Antonia ; Laurenczy, Gbor ; Albrecht, Martin

In: Organometallics, 2009, vol. 28, no. 17, p. 5112–5121

A series of ruthenium(II) complexes have been prepared by using bidentate chelating N-heterocyclic carbene (NHC) ligands that feature different donor groups E (E = olefin, thioether, carboxylate, and NHC). Rigid coordination of all donor sites was concluded from NMR spectroscopy, and the electronic impact of the donor group was evaluated by electrochemical analyses. The chelating donor group had...

Université de Fribourg

On the electronic impact of abnormal C4-bonding in N-heterocyclic carbene complexes

Heckenroth, Marion ; Neels, Antonia ; Garnier, Michael G. ; Aebi, Philipp ; Ehlers, Andreas W. ; Albrecht, Martin

In: Chemistry - A European Journal, 2009///doi: 10.1002/chem.200900249

Sterically similar palladium dicarbene complexes have been synthesized that comprise permethylated dicarbene ligands which bind the metal center either in a normal coordination mode via C2 or abnormally via C4. Due to the strong structural analogy of the complexes, differences in reactivity patterns may be attributed to the distinct electronic impact of normal versus abnormal carbene bonding,...

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

Palladium complexes comprising C(4)-bound diimidazolylidene carbenes

Heckenroth, Marion ; Albrecht, Martin

In: Chimia, 2008, vol. 62, no. 4, p. 253-255

Imidazolium-derived palladium dicarbene complexes have been synthesized which feature either normal C(2) carbene bonding or abnormal C(4) bonding. Comparison of the reactivity of these complexes, in particular towards Lewis acids (H⁺, Ag⁺), indicate consistently that C(4)-bound carbenes are stronger donors than their C(2)-bound analogs. As a consequence of this electronic impact, palladium...