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Mechanisms of the CO2 Insertion into (PCP) Palladium Allyl and Methyl sigma-Bonds. A Kinetic and Computational Study

Johnson, Magnus LU ; Johansson, Roger LU ; Kondrashov, Mikhail LU ; Steyl, Gideon; Ahlquist, Marten S. G.; Roodt, Andreas and Wendt, Ola LU (2010) In Organometallics 29(16). p.3521-3529
Abstract
The reaction of the sigma-bonded (PCP)Pd-Me complex (PCP = 2,6-bis[(di-tert-butylphosphino)methyl]phenyl) with CO2 is first-order in palladium and first-order in CO, with a rate constant k(s) = 8.9 +/- 0.8 M-1 s(-1) at 353 K. Activation parameters are Delta H double dagger = 73 7 kJ/mol and Delta S double dagger = 118 +/- 19 J/K mol. Based on this and theoretical calculations we propose an S(E)2 mechanism where the coordinated methyl group attacks a completely noncoordinated carbon dioxide molecule in a bimolecular reaction. The PCPPd-crotyl complex was synthesized in an 65:35 E:Z mixture, and it was shown to react with CO, to give the complex PCPPd-O(CO)CH(CH3)CHCH2 as a single isomer, where the former gamma-carbon has been carboxylated.... (More)
The reaction of the sigma-bonded (PCP)Pd-Me complex (PCP = 2,6-bis[(di-tert-butylphosphino)methyl]phenyl) with CO2 is first-order in palladium and first-order in CO, with a rate constant k(s) = 8.9 +/- 0.8 M-1 s(-1) at 353 K. Activation parameters are Delta H double dagger = 73 7 kJ/mol and Delta S double dagger = 118 +/- 19 J/K mol. Based on this and theoretical calculations we propose an S(E)2 mechanism where the coordinated methyl group attacks a completely noncoordinated carbon dioxide molecule in a bimolecular reaction. The PCPPd-crotyl complex was synthesized in an 65:35 E:Z mixture, and it was shown to react with CO, to give the complex PCPPd-O(CO)CH(CH3)CHCH2 as a single isomer, where the former gamma-carbon has been carboxylated. Theoretical calculations again suggest an S(E)2 mechanism with a noncoordinated carbon dioxide reacting with the terminal carbon on the allyl group, forming an eta(2)-bonded olefin complex as an intermediate. The rearrangement of this intermediate to the O-bonded product is concluded to be rate determining. The crystal structure of PCPPd-O(CO)C(CH3)(2)CHCH2 is reported and as well as the solubility of carbon dioxide in benzene-d(6) at different pressures and temperatures. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Organometallics
volume
29
issue
16
pages
3521 - 3529
publisher
The American Chemical Society
external identifiers
  • wos:000280794400009
  • scopus:77955700670
ISSN
1520-6041
DOI
10.1021/om100325v
language
English
LU publication?
yes
id
4e6e2467-14c1-4964-8d33-759fd792b50a (old id 1675330)
date added to LUP
2010-09-22 10:03:00
date last changed
2018-07-01 03:24:05
@article{4e6e2467-14c1-4964-8d33-759fd792b50a,
  abstract     = {The reaction of the sigma-bonded (PCP)Pd-Me complex (PCP = 2,6-bis[(di-tert-butylphosphino)methyl]phenyl) with CO2 is first-order in palladium and first-order in CO, with a rate constant k(s) = 8.9 +/- 0.8 M-1 s(-1) at 353 K. Activation parameters are Delta H double dagger = 73 7 kJ/mol and Delta S double dagger = 118 +/- 19 J/K mol. Based on this and theoretical calculations we propose an S(E)2 mechanism where the coordinated methyl group attacks a completely noncoordinated carbon dioxide molecule in a bimolecular reaction. The PCPPd-crotyl complex was synthesized in an 65:35 E:Z mixture, and it was shown to react with CO, to give the complex PCPPd-O(CO)CH(CH3)CHCH2 as a single isomer, where the former gamma-carbon has been carboxylated. Theoretical calculations again suggest an S(E)2 mechanism with a noncoordinated carbon dioxide reacting with the terminal carbon on the allyl group, forming an eta(2)-bonded olefin complex as an intermediate. The rearrangement of this intermediate to the O-bonded product is concluded to be rate determining. The crystal structure of PCPPd-O(CO)C(CH3)(2)CHCH2 is reported and as well as the solubility of carbon dioxide in benzene-d(6) at different pressures and temperatures.},
  author       = {Johnson, Magnus and Johansson, Roger and Kondrashov, Mikhail and Steyl, Gideon and Ahlquist, Marten S. G. and Roodt, Andreas and Wendt, Ola},
  issn         = {1520-6041},
  language     = {eng},
  number       = {16},
  pages        = {3521--3529},
  publisher    = {The American Chemical Society},
  series       = {Organometallics},
  title        = {Mechanisms of the CO2 Insertion into (PCP) Palladium Allyl and Methyl sigma-Bonds. A Kinetic and Computational Study},
  url          = {http://dx.doi.org/10.1021/om100325v},
  volume       = {29},
  year         = {2010},
}