Abstract
The synthesis of a series of [(IPr)Pd(R-acac)Cl] precatalysts (acac=acetylacetonato: IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), where the acac ligand on palladium has been systematically modified through terminal substitution, is reported. The following substituted acac ligands are employed in this study: dibenzoylmethanato (dbm), benzoylacelonato (bac), tetramethylheptanedionato (tmhd), and hexafluoroace tylacetonato (hfac). Full spectroscopic characterization of the new complexes is provided along with X-ray studies for three of these. Investigation of their catalytic activity in cross-coupling is also presented through a comparative study in an aryl amination reaction. The catalytic results show a strong correlation between the increased steric bulk of the acac substituents and an increased activation rate of the precatalyst, going from the acac to the tmhd ligand. This observation, along with the inertness of the Iliac compound, seems to support our previous proposal for the activation mechanism of these complexes under cross-coupling conditions.
Original language | English |
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Pages (from-to) | 841-846 |
Number of pages | 6 |
Journal | Chemistry-An Asian Journal |
Volume | 5 |
Issue number | 4 |
DOIs | |
Publication status | Published - 2010 |
Keywords
- activation
- amination
- cross-coupling
- N-heterocyclic
- carbenes
- palladium
- CROSS-COUPLING REACTIONS
- N-HETEROCYCLIC CARBENE
- TEMPERATURE SUZUKI-MIYAURA
- ROOM-TEMPERATURE
- PALLADIUM(II) COMPLEXES
- (NHC)PD(ALLYL)CL NHC
- REDUCTIVE ELIMINATION
- OXIDATIVE ADDITION
- BUCHWALD-HARTWIG
- ACETONE DBA