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The Rate‐Determining Step in the Rhodium–Xantphos‐Catalysed Hydroformylation of 1‐Octene
Author(s) -
Zuidema Erik,
Escorihuela Laura,
Eichelsheim Tanja,
Carbó Jorge J.,
Bo Carles,
Kamer Paul C. J.,
van Leeuwen Piet W. N. M.
Publication year - 2008
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.200700727
Subject(s) - hydroformylation , dissociation (chemistry) , rhodium , chemistry , xantphos , catalysis , kinetic isotope effect , hydride , alkene , octene , photochemistry , medicinal chemistry , computational chemistry , organic chemistry , hydrogen , deuterium , physics , palladium , quantum mechanics , ethylene
The rate‐determining step in the hydroformylation of 1‐octene, catalysed by the rhodium–Xantphos catalyst system, was determined by using a combination of experimentally determined 1 H/ 2 H and 12 C/ 13 C kinetic isotope effects and a theoretical approach. From the rates of hydroformylation and deuterioformylation, a small 1 H/ 2 H isotope effect of 1.2 was determined for the hydride moiety of the rhodium catalyst. 12 C/ 13 C isotope effects of 1.012(1) and 1.012(3) for the α‐carbon and β‐carbon atoms of 1‐octene were determined, respectively. Both quantum mechanics/molecular mechanics (QM/MM) and full quantum mechanics calculations were carried out on the key catalytic steps, for “real‐world” ligand systems, to clarify whether alkene coordination or hydride migration is the rate‐determining step. Our calculations (21.4 kcal mol −1 ) quantitatively reproduce the experimental energy barrier for CO dissociation (20.1 kcal mol −1 ) starting at the (bisphosphane)RhH(CO) 2 resting state. The barrier for hydride migration lies 3.8 kcal mol −1 higher than the barrier for CO dissociation (experimentally determined trend ∼3 kcal mol −1 ). The computed 1 H/ 2 H and 12 C/ 13 C kinetic isotope effects corroborate the results of the energy analysis.