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Computational Study of a New Heck Reaction Mechanism Catalyzed by Palladium( II / IV ) Species
Author(s) -
Sundermann Andreas,
Uzan Olivier,
Martin Jan M. L.
Publication year - 2001
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 - 10.1002/1521-3765(20010417)7:8<1703::aid-chem17030>3.0.co;2-k
Subject(s) - oxidative addition , palladium , reductive elimination , catalysis , chemistry , ligand (biochemistry) , density functional theory , reaction mechanism , denticity , heck reaction , mechanism (biology) , octahedron , catalytic cycle , computational chemistry , photochemistry , combinatorial chemistry , crystallography , organic chemistry , ion , crystal structure , physics , receptor , biochemistry , quantum mechanics
In this theoretical study on the Heck reaction we explore the feasibility of an alternative pathway that involves a Pd II /Pd IV redox system. Usually, the catalytic cycle is formulated based on a Pd 0 /Pd II mechanism. We performed quantum chemical calculations using density functional theory on a model system that consisted of diphosphinoethane (DPE) as a bidentate ligand and the substrates ethylene and phenyl iodide to compare both mechanisms. Accordingly, the Pd II /Pd IV mechanism is most likely to occur in the equatorial plane of an octahedral Pd IV complex. The energy profiles of both reaction pathways under consideration are largely parallel. A major difference is found for the oxidative addition of the C−I bond to the palladium centre. This is a rate‐determining step of the Pd II /Pd IV mechanism, while it is facile for a Pd 0 catalyst. The calculations show that intermediate ligand detachment and re‐attachment is necessary in the course of the oxidative addition to Pd II . Therefore, we expect the Pd II /Pd IV mechanism to be only feasible if a weakly coordinating ligand is present.