SummaryNew Pd–NHC complexes have been synthesized and employed for palladium-catalyzed direct arylation of pyrrole derivatives by using electron-deficient aryl chlorides as coupling partners. The desired coupling products were obtained in moderate to good yields by using 1 mol % of these air-stable palladium complexes. This is an advantage compared to the procedures employing air-sensitive phosphines, which have been previously shown to promote the coupling of aryl chlorides with heteroarenes.

Novel benzimidazol-2-ylidene carbene complexes of Ag(I) were prepared by interaction of the corresponding benzimidazolium salt with Ag 2 O in dichloromethane. Their structures were characterized by elemental analyses, 1 H-NMR, 13 C-NMR and IR spectroscopy techniques. All compounds studied in this work were screened for their in vitro antimicrobial activities against the standard strains: Enterococcus faecalis (ATCC 29212), Staphylococcus aureus (ATCC 29213), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853) and the fungi Candida albicans and Candida tropicalis. The new complexes were found to be effective antimicrobial activity against a series of bacteria and fungi.

The reaction of 2-(2-bromoethyl)-1,3-dioxane with 1-alkylbenzimidazole derivatives results in the formation of the new benzimidazolium salts (1). The reaction of Pd(OAc) 2 with 1,3-dialkylbenzimidazolium salts (1a-c) yields palladium N-heterocyclic carbene (NHC) complexes (2a-c). All synthesized compounds were characterized by 1 H NMR, 13 C NMR, IR and elemental analysis techniques which support the proposed structures. As catalysts, these new palladium complexes offer a simple and efficient methodology for the synthesis of triarylamines and secondary amines from anilines and amines and in a single step with potassium tertiary butoxide as a base.

The reaction of Pd(OAc)2 with 1-(benzhydryl)-3-(alkyl)benzimidazolium salts 1a-d yields trans-bis[1-(benzhydryl)-3-(alkyl)benzimidazolin-2-ylidene]dibromopalladium(II) complexes (2a-d) which were characterized by elemental analysis, NMR spectroscopy and the molecular structures of 2b, and 2d were determined by X-ray crystallography. The catalytic activity of PdBr2bis(benzimidazolin-2-ylidene) complexes 2a-d was evaluated in the direct arylation reaction of benzothiazole with bromobenzene derivatives.

Novel ruthenium-1,3-dialkylimidazolin-2-ylidene complexes (2a-e) have been prepared and characterized by C, H, N analysis, 1 H-NMR and 13 C-NMR. The ortho position of the aromatic ring of pyridyl group substituted aromatic compound was directly arylated with aryl bromides and chlorides in the presence of a catalytic amount of [RuCl 2 (1,3-dialkylimidazolin-2-ylidene)] complexes.