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The insertion of carbon dioxide into metal element σ-bonds is an important elementary step in many catalytic reactions for carbon dioxide valorization. Here, the insertion of carbon dioxide into a family of group 10 alkyl complexes of the type ( R PBP)M(CH 3 ) ( R PBP = B(NCH 2 PR 2 ) 2 C 6 H 4 − ; R = Cy or t Bu; M = Ni or Pd) to generate κ 1 -acetate complexes of the form ( R PBP)M{OC(O)CH 3 } is investigated. This involved the preparation and characterization of a number of new complexes supported by the unusual R PBP ligand, which features a central boryl donor that exerts a strong trans -influence, and the identification of a new decomposition pathway that results in C–B bond formation. In contrast to other group 10 methyl complexes supported by pincer ligands, carbon dioxide insertion into ( R PBP)M(CH 3 ) is facile and occurs at room temperature because of the high trans -influence of the boryl donor. Given the mild conditions for carbon dioxide insertion, we perform a rare kinetic study on carbon dioxide insertion into a late-transition metal alkyl species using ( t Bu PBP)Pd(CH 3 ). These studies demonstrate that the Dimroth–Reichardt parameter for a solvent correlates with the rate of carbon dioxide insertion and that Lewis acids do not promote insertion. DFT calculations indicate that insertion into ( t Bu PBP)M(CH 3 ) (M = Ni or Pd) proceeds via an S E 2 mechanism and we compare the reaction pathway for carbon dioxide insertion into group 10 methyl complexes with insertion into group 10 hydrides. Overall, this work provides fundamental insight that will be valuable for the development of improved and new catalysts for carbon dioxide utilization.
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Insertion of CO 2 Mediated by a (Xantphos)Ni I –Alkyl Species
Abstract The incorporation of CO2into organometallic and organic molecules represents a sustainable way to prepare carboxylates. The mechanism of reductive carboxylation of alkyl halides has been proposed to proceed through the reduction of NiIIto NiIby either Zn or Mn, followed by CO2insertion into NiI‐alkyl species. No experimental evidence has been previously established to support the two proposed steps. Demonstrated herein is that the direct reduction of (tBu‐Xantphos)NiIIBr2by Zn affords NiIspecies. (tBu‐Xantphos)NiI‐Me and (tBu‐Xantphos)NiI‐Et complexes undergo fast insertion of CO2at 22 °C. The substantially faster rate, relative to that of NiIIcomplexes, serves as the long‐sought‐after experimental support for the proposed mechanisms of Ni‐catalyzed carboxylation reactions.
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- Award ID(s):
- 1654483
- PAR ID:
- 10117080
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 58
- Issue:
- 39
- ISSN:
- 1433-7851
- Page Range / eLocation ID:
- p. 13865-13868
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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