We present several cyclometalated palladium 2-phenylimidazole carbene complexes with different N-1 groups as well as different substituents at the C-2 phenyl group of the cyclometalating imidazole. These complexes were synthesized from the corresponding dimeric palladacycles which were obtained from palladium acetate and 1,2-diarylimidazoles.For the syntheses of the ligands we developed a new, high-yielding and versatile procedure that allows for the preparation of 1,2-diarylimdazoles with sterically demanding substituents starting from inexpensive anilines und carboxylic acids. We were able to prepare imidazoles with 2,6-diisopropylphenyl, 2,6-diphenylphenyl as well as 4-bromo-2,6-dimethylphenyl N-1 groups or with 4-methoxyphenyl, 4-fluorophenyl, naphth-1-yl or thiophen-2-yl C-2 groups.The catalytic activity of the complexes was explored in the Suzuki-Miyaura cross coupling reaction of aryl chlorides. The investigated complexes showed a high catalytic activity, in most cases the aryl chloride was fully converted within 1 hour with 0.2 (or less) mol% of the complex. For the most active complex we will demonstrate a wide substrate scope, several aryl as well as benzyl chlorides could be coupled with different boronic acids in excellent yields using very low catalyst concentrations (up to 0.01 mol%).

Cyclometalated palladium 2-phenylimidazole carbene complexes and their catalytic performance in the Suzuki-Miyaura cross coupling reaction

247th National Meeting (2014)

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