Synthetic and antimicrobial studies on new gold(I) complexes of imidazolidin‐2‐ylidenes

Abstract

Six new 1,3-diorganylimidazolidin-2-ylidene (NHC) gold(I) complexes of the type [Au(NHC) 2 ] + (1-6), were synthesized by reacting [AuCl(PPh) 3 ] with 1,3-dimesitylimidazolidin-2-ylidene or bis(1,3-dialkylimidazolidin-2-ylidene). The complexes 1-6 were fully characterized by elemental analyses and spectroscopic data. The placement of mesityl or para-substituted benzyl groups on the nitrogen atoms of the ring of the complexes leads to the particularly active antibacterial agents evaluated in this work. It is worth noting that the p-methoxybenzyl derivative (2) inhibited the growth of Pseudomona aeruginosa, Staphylococcus epidermidis, Staphylococcus aureus and Enterococcus faecalis with minimum inhibitory concentration (MIC) values of 3.12 µg ml −1 , 6.25 µg ml −1 , 3.12 µg ml −1 and 3.12 µg ml −1 respectively. In contrast, the analogous p-dimethylaminobenzyl derivative (3) is effective only against Escherichia coli (MIC = 3.12 µg ml −1 ).

Rotamers of palladium complexes bearing IR active N-heterocyclic carbene ligands: Synthesis, structural characterization and catalytic activities

“…However, reaction of the cyanoethyl substituted imidazolium salt 1b under similar reaction conditions gave the monocarbene complex [PdBr 2 ( etCN NHC)(imd)] (5) with a N-coordinated mesitylimidazole ligand (imd), which presumably resulted from N-C cleavage of the ß-cyanoethyl group under the basic and relatively harsh reaction condition [6]. Similar cleavage was observed in the analogous reaction of the esterethyl substituted imidazolium salt 2b resulting in complex [PdBr 2 ( etCO2Me NHC)(imd)] (6) (Scheme 3b).…”

“…All Pd-NHC complexes (3)(4)(5)(6), were fully characterized by electrospray ionization (ESI) mass spectrometry, IR, 1 H and 13 C NMR spectroscopies. In the ESI mass spectra of the bis(carbene) complexes 3 and 4, m/z values corresponding to both [MÀBr] 4 ] + for 4b) fragments were observed, with the latter as the base peak.…”

“…Moreover, additional functionalities can be introduced at the nitrogen atoms of the N-heterocyclic ring in a straightforward manner, and accordingly, various donor-functionalized NHCs and their complexes have been explored [2], some of which show hemilabile behaviour [3]. In addition to their extensive use in catalysis, some NHC complexes of Ag, Au and Pd have also been investigated for potential biomedical applications [4][5][6][7][8]. Furthermore, application of NHCs in material science [9] and supramolecular chemistry [10] are just beginning to unfold.…”

Polyisobutylene-supported N-heterocyclic carbene palladium catalysts

“…4.6. 1,phenyl)imidazolium chloride (8) In a 100-mL round-bottomed flask, equipped with a magnetic stir bar and a rubber septum, N,N 0 -bis(2,6-diisopropyl-4-polyisobutylphenyl)ethylenediimine (6.3 g, 2.6 mmol) was dissolved in 25 mL of THF. Chloromethyl ethyl ether (0.25 g, 2.6 mmol) was added and the mixture was heated to 40 C for 20 h. The solvent was removed under reduced pressure and the residue was purified by column chromatography (eluted first with CH 2 Cl 2 and then with 9:1 solution of CH 2 Cl 2 and methanol).…”

“…These properties led to many other studies that demonstrated that NHC-metal complexes have reactivities similar to those of phosphineemetal complexes, often with better air and moisture stability . NHC ligands can form stable bonds with metals and phosphineemetal complexes are sometimes used as precursors for NHC-metal complexes [7,8]. These properties of NHC ligands have led to many examples of metal complexes of these electron-rich ligands, NHC ligated complexes that are often used in homogeneous catalysis using transition metals like palladium, ruthenium, rhodium, gold, copper, and nickel [2].…”