Mechanisms in the Reaction of Palladium(II)–π-Allyl Complexes with Aryl Halides: Evidence for NHC Exchange Between Two Palladium Complexes

✍ Scribed by Adrien T. Normand; Mikhail S. Nechaev; Kingsley J. Cavell

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 505 KB
• Volume: 15
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200900373

✦ Synopsis

Abstract

A detailed experimental and DFT study (PBE level) of the reaction of [Pd(η^3^‐C~3~H~5~)(tmiy)(PR~3~)]BF~4~ (tmiy=tetramethylimidazolin‐2‐ylidene, PR~3~=phosphane), precursors to monoligated Pd^0^ species, with aryl electrophiles yielding 2‐arylimidazolium salt is reported. Experiments establish that an autocatalytic ligand transfer mechanism is preferred over Pd^IV^ and σ‐bond metathesis pathways, and that transmetalation is the rate‐determining step. Calculations indicate that the key step involves the concerted exchange of NHC and iodo ligands between two different Pd^II^ complexes. This is corroborated by experimental results showing the slower reaction of complexes containing the bulkier dipdmiy (dipdmiy = diisopropyldimethylimidazolin‐2‐ylidene).