Synthesis, structure and catalytic application of palladium(II) complexes bearing N-heterocyclic carbenes and phosphines

A variety of mixed palladium(II) complexes bearing N-heterocyclic carbenes (NHCs) and triaryl- and trialkylphosphines [NHC(R-2)]Pd(PR'(3))I-2 (R = Me, t-Bu, (R)-1-phenylethyl; R' = Ph, o-tolyl, cyclohexyl, t-Bu) have been prepared. Crystal structure details of trans-diiodo(1,3-di-tert-butylimidazolin-2-ylidene)(triphenylphosphino)palladium(II) are presented. The complexes were tested as catalysts in the Mizoroki-Heck, Suzuki-Miyaura and Stille reactions as well as in the dimerization of phenylacetylene. In catalytic studies of the Suzuki-Miyaura cross-coupling reaction, the performance of these novel complexes was compared to the results obtained by the corresponding bis(NHC) and bis(phosphine) complexes. (C) 2001 Elsevier Science B.V. All rights reserved.