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Competing reaction mechanisms for the carbonylation of neutral palladium(II) complexes containing bidentate ligands: a theoretical study
journal contribution
posted on 2023-05-16, 10:53 authored by Frankcombe, KE, Cavell, KJ, Brian YatesBrian Yates, Knott, RBThe complete carbonylation mechanism for the model palladium(II) system, Pd(PH3)(CH3)-(N-O) + CO → Pd(PH3)(COCH3)(N-O) (N-O = NHCHCOO-), has been investigated employing nonlocal density functional theory (DFT) and second-order Mø11er-Plesset perturbation theory (MP2). Four possible mechanisms were identified, all involving the initial displacement of the phosphine ligand by carbon monoxide via a trigonal bipyramidal transition structure. Of these four mechanisms, the rate-determining methyl migration step was found to be lowest in energy when proceeding from a novel five-coordinate intermediate in which the palladium-nitrogen bond is weakened (2.385 Å at the MP2 level of theory). This mechanism is consistent with the available experimental data. MP2 calculations using large basis sets predicted an overall exothermicity of -59.7 kJ/mol and a negligible activation energy of +6.0 kJ/mol with respect to the separated reactants. In addition, a novel transition structure that accounts for the isomerization of square-pyramidal d8 complexes is presented.
History
Publication title
OrganometallicsVolume
16Issue
14Pagination
3199-3206ISSN
0276-7333Department/School
School of Natural SciencesPublisher
American Chemical SocietyPlace of publication
USARepository Status
- Restricted