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Evidence for a Cooperative Mechanism Involving Two Palladium(0) Centers in the Oxidative Addition of Iodoarenes
Author(s) -
Perego Luca Alessandro,
Payard PierreAdrien,
Haddou Baptiste,
Ciofini Ilaria,
Grimaud Laurence
Publication year - 2018
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.201704899
Subject(s) - oxidative addition , chemistry , cationic polymerization , palladium , kinetics , density functional theory , imidazole , oxidative phosphorylation , polar effect , metal , medicinal chemistry , photochemistry , stereochemistry , catalysis , computational chemistry , polymer chemistry , organic chemistry , biochemistry , physics , quantum mechanics
Oxidative addition of iodoarenes (ArI) to Pd 0 ligated by 1‐methyl‐1 H ‐imidazole (mim) in polar solvents leads to cationic arylpalladium(II) complexes [ArPd(mim) 3 ] + . Kinetic analyses evidence that this reaction is second order with respect to the concentration of Pd 0 , and a mechanism involving the cooperative intervention of two Pd 0 centers has been postulated to explain this finding. This unusual behavior is also observed with other nitrogen‐containing ligands and it is general for iodobenzenes substituted with electron‐donating or weakly electron‐withdrawing groups. In contrast, bromoarenes and electron‐poor iodoarenes display first‐order kinetics with respect to Pd 0 . Theoretical calculations performed at the density functional theory (DFT) level suggest the existence of mim‐ligated ArI‐Pd 0 complexes, in which the iodoarene is bound to the metal in a halogen‐bond‐like fashion. Coordination weakens the C−I bond and facilitates the oxidative insertion of another Pd 0 center across this C−I bond. This conceptually novel mechanism, involving the cooperative participation of two distinct metal centers, allows a full explanation of the experimentally observed kinetics.