Modified [(IPr)Pd(R-acac)Cl] complexes: influence of the acac substitution on the catalytic activity in aryl amination.
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), benzoylacetonato (bac), tetramethylheptanedionato (tmhd), and hexafluoroacetylacetonato (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 hfac compound, seems to support our previous proposal for the activation mechanism of these complexes under cross-coupling conditions.
Marion
Nicolas
N
Department of Chemistry, University of New Orleans, 2000 Lakeshore Drive, New Orleans, Louisiana 70148, USA.
Navarro
Oscar
O
Stevens
Edwin D
ED
Ecarnot
Elise C
EC
Bell
Andrew
A
Amoroso
Dino
D
Nolan
Steven P
SP
D000586:Amination; D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry; D008024:Ligands; D008968:Molecular Conformation; D010165:Palladium / Q000737:chemistry*
D056831:Coordination Complexes; D006571:Heterocyclic Compounds; D008024:Ligands; D010165:Palladium