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Gas‐Phase Energetics of Reductive Elimination from a Palladium(II) N‐Heterocyclic Carbene Complex
Author(s) -
Couzijn Erik P. A.,
Zocher Eva,
Bach Andreas,
Chen Peter
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902929
Subject(s) - reductive elimination , chemistry , carbene , dissociation (chemistry) , palladium , collision induced dissociation , fragmentation (computing) , density functional theory , ligand (biochemistry) , bond dissociation energy , computational chemistry , photochemistry , tandem mass spectrometry , mass spectrometry , organic chemistry , catalysis , biochemistry , receptor , chromatography , computer science , operating system
Energy‐resolved collision‐induced dissociation experiments using tandem mass spectrometry are reported for an phenylpalladium N‐heterocyclic carbene (NHC) complex. Reductive elimination of an NHC ligand as a phenylimidazolium ion involves a barrier of 30.9(14) kcal mol −1 , whereas competitive ligand dissociation requires 47.1(17) kcal mol −1 . The resulting three‐coordinate palladium complex readily undergoes reductive CC coupling to give the phenylimidazolium π complex, for which the binding energy was determined to be 38.9(10) kcal mol −1 . Density functional calculations at the M06‐L//BP86/TZP level of theory are in very good agreement with experiment. In combination with RRKM modeling, these results suggest that the rate‐determining step for the direct reductive elimination process switches from the CC coupling step to the fragmentation of the resulting σ complex at low activation energy.