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Abstract We report that Ni(COD)(DQ) (COD=1,5‐cyclooctadiene, DQ=duroquinone), an air‐stable 18‐electron complex originally described by Schrauzer in 1962, is a competent precatalyst for a variety of nickel‐catalyzed synthetic methods from the literature. Due to its apparent stability, use of Ni(COD)(DQ) as a precatalyst allows reactions to be conveniently performed without use of an inert‐atmosphere glovebox, as demonstrated across several case studies.
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Ligand substitution and electronic structure studies of bis(phosphine)cobalt cyclooctadiene precatalysts for alkene hydrogenation
Diene self-exchange reactions of the 17-electron, formally cobalt(0) cyclooctadienyl precatalyst, (R,R)-(iPrDuPhos)Co(COD) (P2CoCOD, (R,R)-iPrDuPhos = 1,2-bis((2R,5R)-2,5-diisopropylphospholano)benzene, COD = 1,5-cyclooctadiene) were studied using natural abundance and deuterated 1,5-cyclooctadiene. Exchange of free and coordinated diene was observed at ambient temperature in benzene-d6 solution and kinetic studies support a dissociative process. Both neutral P2CoCOD and the 16-electron, cationic cobalt(I) complex, [(R,R)-(iPrDuPhos)Co(COD)][BArF4] (BArF4 = B[(3,5-(CF3)2)C6H3]4) underwent instantaneous displacement of the 1,5-cyclooctadiene ligand by carbon monoxide and generated the corresponding carbonyl derivatives. The solid-state parameters, DFT-computed Mulliken spin density and analysis of molecular orbitals suggest an alternative description of P2CoCOD as low-spin cobalt(II) with the 1,5-cyclooctadiene acting as a LX2-type ligand. This view of the electronic structure provides insight into the nature of the ligand substitution process and the remarkable stability of the neutral cobalt complexes toward protic solvents observed during catalytic alkene hydrogenation.
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- Award ID(s):
- 1855719
- PAR ID:
- 10209973
- Date Published:
- Journal Name:
- Canadian Journal of Chemistry
- ISSN:
- 0008-4042
- Page Range / eLocation ID:
- 1 to 9
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1139/cjc-2020-0352
