New Pd-NHC-complexes for the Mizoroki-Heck reaction

The synthesis and structural characterization of novel chelating N-aryl substituted palladium(II)-biscarbene-complexes is reported: 1,1'-bis(4-bromophenyl)-3,3'-methylene-diimidazoline-2,2'-diylidene-palladium(II)-dibromide, 1,1'-bis(4-methoxyphenyl)-3,3'-methylenediimidazoline-2,2'-diylidene-palladium(II)-dibromide and 1,1'-bis(4-n-butoxyphenyl)-3,3'-methylenediimidazoline-2,2'-diylidene-palladium(II)-dibromide have been synthesized in good yields. The catalytic activity of these 1,1'-aryl-3,3'-methylenediimidazoline-2, 2'-diylidene-palladium(II)-dihalogenide complexes was tested for the Mizoroki-Heck reaction in comparison to 1,1'-(bis)methyl-3, 3'-methylenediimidazoline-2,2'-diylidene-palladium(II)-dihalogenide complexes and to 1,1'-bis(phenyl)-3,3'-methylene-diimidazoline-2,2'-diylidene-palladium(II) -dibromide. The activity of the aryl substituted catalysts is significantly higher compared to the methyl substituted NHC complexes. They also allow the coupling of arylchlorides with olefins. (c) 2006 Elsevier B.V. All rights reserved.