- [Bis(oxazolinyl)pyrrole]palladium Complexes as Catalysts in Heck- and Suzuki-Type C-C Coupling Reactions
Clément Mazet, Lutz H. Gade*
Eur. J. Inorg. Chem. 2003, 1161-1168
The two bis(oxazoline)pyrrole ligand precursors 2,5-bis(4,4′-dimethyl-4,5-dihydrooxazol-2-yl)pyrrole (“dmoxpH”, 2) and 2,5-bis(4,4′-dimethyl-4,5-dihydrooxazol-2-yl)-3,4-diethylpyrrole (“Et2dmoxpH”, 5) have been synthesised and metallated by treatment with n-butyllithium at −78 °C in diethyl ether. Treatment of the lithium pyrrolide with 1.1 mol-equiv. of [PdCl2(COD)] gave the corresponding helical dinuclear palladium complexes [Pd2Cl2(dmoxp)2] (6) and [Pd2Cl2(Et2dmoxp)2] (7). In both complexes the tridentate bis(oxazolinyl)pyrrolide ligands bridge the two metal centres, with one of the oxazoline rings and the charged pyrrolide being coordinated to the one Pd centre while the second oxazoline ring is twisted relative to the pyrrolide unit and coordinates to the second palladium atom. Complexes 6 and 7 were found to be precursors for active catalysts for Heck coupling reactions of styrene and ethyl acrylate, with turnover numbers of over 9000 for the former, as well as for disubstituted alkenes such as methyl crotonate and methyl cinnamate. Complex 6 was found to be a very active catalyst for Suzuki coupling reactions of activated and deactivated bromoarenes.
open archive unige:7919
Editor’s version DOI: 10.1002/ejic.200390148