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Active Anionic Zero‐Valent Palladium Catalysts: Characterization by Density Functional Calculations
Author(s) -
Kozuch Sebastian,
Shaik Sason,
Jutand Anny,
Amatore Christian
Publication year - 2004
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.200306056
Subject(s) - denticity , palladium , chemistry , density functional theory , catalysis , crystallography , dissociation (chemistry) , computational chemistry , bond dissociation energy , stereochemistry , medicinal chemistry , crystal structure , organic chemistry
This works uses DFT (B3LYP/LACVP* + //B3LYP/LACVP* level) to ascertain the existence of the tricoordinate, anionic zero‐valent palladium complexes that were postulated as the active species in the catalytic cycles of Pd‐catalyzed Heck and cross‐coupling reactions. The variety of complexes studied ( 1 and 2 ), include [Pd(PR 3 ) 2 X] − species, in which R=H, Me, vinyl, and phenyl, and X=Cl, Br, I, AcO, and TFA, as well as bidentate complexes, [Pd{Ph 2 P(CH 2 ) n Ph 2 P}X] − , in which X=Cl, AcO and n =3–6. The study shows that these complexes exist as distinct minima in the gas phase as well as in THF. In addition, it provides geometric features and PdX − dissociation energies for all these complexes as well as some NMR and IR data, which show a clear distinction in these features between the tri‐ and dicoordinate Pd 0 species. An orbital interaction model and perturbation theory arguments account for the bonding mechanism and rationalize all the trends in the stability of the PdX bond. These trends include the effects of variation of X, R, and the length of the linker in the bidentate ligands.