Pierre de Frémont

Synthesis and characterization of oxygen-functionalised-NHC silver(I) complexes and NHC transmetallation to nickel(II)

The new alcohol- and ether-functionalised-NHC silver(I) complexes bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImDiPP(C2OH)}2]Cl (4), bis(1-(2-hydroxyethyl)-3-mesityl-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImMes(C2OH)}2]Cl (5), bis(1-(2-hydroxyethyl)-3-methyl-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImMe(C2OH)}2]Cl (6), bis(1-(2,6-diisopropylphenyl)-3-(2-hydroxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) tetrafluoroborate, [Ag{ImDiPP(C2OH)}2]BF4 (9), and bis(1-(2,6-diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)silver(I) chloride, [Ag{ImDiPP(C2OMe)}2]Cl (13), were synthesized and fully characterized by NMR spectroscopy and single crystal X-ray diffraction. For some complexes, an uncommon heteronuclear coupling (4)J((107/109)Ag-H) was unveiled. Their ability to transfer the NHC ligand to Ni(II) was assessed in the presence of different nickel(II) sources; the bis-NHC Ni(II) complex bis(1-(2,6-diisopropylphenyl)-3-(2-methoxyethyl)-1H-imidazol-2(3H)-ylidene)nickel(II) chloride, [NiCl2{ImDiPP(C2OMe)}2] (15), was obtained from 13 and shown by X-ray diffraction study to have a trans-arrangement of the two NHC ligands. However, in contrast to other Ag(I) NHC complexes the transmetallation reaction failed with the hydroxyl-functionalised silver complexes, possibly due to the acidity of the alcohol OH function, leading overall to reprotonation of the C(NHC) and isolation of the corresponding imidazolium salts.

High-Throughput Screening of Metal-N-Heterocyclic Carbene Complexes against Biofilm Formation by Pathogenic Bacteria.

A set of molecules including a majority of metal‐N‐heterocyclic carbene (NHC) complexes (metal=Ag, Cu, and Au) and azolium salts were evaluated by high‐throughput screening of their activity against biofilm formation associated with pathogenic bacteria. The anti‐planktonic effects were compared in parallel. Representative biofilm‐forming strains of various genera were selected (Listeria, Pseudomonas, Staphylococcus, and Escherichia). All the compounds were tested at 1 mg L−1 by using the BioFilm Ring Test. An information score (IS, sum of the activities) and an activity score (AS, difference between anti‐biofilm and anti‐planktonic activity) were determined from normalized experimental values to classify the most active molecules against the panel of bacterial strains. With this method we identified lipophilic AgI and CuI complexes possessing aromatic groups on the NHC ligand as the most efficient at inhibiting biofilm formation.

Synthesis, Characterization and Catalytic Activity of NHC Gold(I) Polyoxometalate Complexes

The new hybrid NHC gold(I) acetonitrile polyoxometalate complexes {[Au(IPr)(MeCN)+ ][H+ ]3 [SiW12 O404- ] (1), [Au(IPr)(MeCN)+ ][H+ ]2 [PMo12 O403- ] (2), [Au(IPr)(MeCN)+ ][H+ ]5 [P2 W18 O626- ] (3), [Au(IPr)(MeCN)+ ][H+ ]2 [PW12 O403- ] (4), [Au(IPr)(MeCN)+ ]3 [PMo12 O403- ] (5) and [Au(ItBu)(MeCN)+ ] [H+ ]2 [PMo12 O403- ] (6)} were readily synthesized in high yield and characterized by NMR and MS-ESI spectroscopy. In a preliminary catalytic study, their activity was assessed under heterogeneous conditions for the ene-yne rearrangement reaction and a cycloisomerization reaction. Additionally, their reactivity and recyclability were tested in the hydration of alkynes under homogeneous conditions.