Cationic iridium complexes bearing imidazol-2-ylidene ligands as transfer hydrogenation catalysts

Anna C. Hillier, Hon Man Lee, Edwin D. Stevens, Steven P. Nolan

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Abstract

The synthesis and characterization by X-ray crystallography of the complexes [Ir(cod)-(py)(L)]PF6 (L = IMes, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (2); L = IPr, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (3); L = ICy, 1,3-bis(cyclohexyl)imidazol-2-ylidene (4)) are reported. Complexes 2-4 have been employed as catalysts for transfer hydrogenation reactions from 2-propanol to a number of unsaturated substrates and their activity compared with that of the related cationic iridium(I) species [Ir(cod)(py)(SIMes)]PF6 (1), [Ir(cod)(py)(PCy3)]PF6 (5), and complexes formed in situ from [Ir(cod)(py)2]PF6 and diazabutadienes (RN=CHCH=NR, DAB-R; R = cyclohexyl, DAB-Cy; R = 2,4,6-trimethylphenyl, DAB-Mes; R = adamantyl, DAB-Ad; R = 2,4,6-trimethoxyphenyl, DAB-trimethoxyphenyl). All complexes tested were found to be active catalysts for transfer hydrogenation of ketones, with complex 4 displaying the highest activity. Complex 4 also exhibits moderate activity toward simple olefins and an aromatic nitro compound.

Original languageEnglish
Pages (from-to)4246-4252
Number of pages7
JournalOrganometallics
Volume20
Issue number20
DOIs
Publication statusPublished - 2001 Oct 1

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Bearings (structural)
Iridium
iridium
imidazoles
Hydrogenation
hydrogenation
Nitro Compounds
Ligands
catalysts
ligands
Catalysts
2-Propanol
X ray crystallography
Alkenes
Ketones
nitro compounds
ketones
alkenes
crystallography
Substrates

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

Cite this

Hillier, Anna C. ; Lee, Hon Man ; Stevens, Edwin D. ; Nolan, Steven P. / Cationic iridium complexes bearing imidazol-2-ylidene ligands as transfer hydrogenation catalysts. In: Organometallics. 2001 ; Vol. 20, No. 20. pp. 4246-4252.
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Cationic iridium complexes bearing imidazol-2-ylidene ligands as transfer hydrogenation catalysts. / Hillier, Anna C.; Lee, Hon Man; Stevens, Edwin D.; Nolan, Steven P.

In: Organometallics, Vol. 20, No. 20, 01.10.2001, p. 4246-4252.

Research output: Contribution to journalArticle

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AU - Lee, Hon Man

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AB - The synthesis and characterization by X-ray crystallography of the complexes [Ir(cod)-(py)(L)]PF6 (L = IMes, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (2); L = IPr, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (3); L = ICy, 1,3-bis(cyclohexyl)imidazol-2-ylidene (4)) are reported. Complexes 2-4 have been employed as catalysts for transfer hydrogenation reactions from 2-propanol to a number of unsaturated substrates and their activity compared with that of the related cationic iridium(I) species [Ir(cod)(py)(SIMes)]PF6 (1), [Ir(cod)(py)(PCy3)]PF6 (5), and complexes formed in situ from [Ir(cod)(py)2]PF6 and diazabutadienes (RN=CHCH=NR, DAB-R; R = cyclohexyl, DAB-Cy; R = 2,4,6-trimethylphenyl, DAB-Mes; R = adamantyl, DAB-Ad; R = 2,4,6-trimethoxyphenyl, DAB-trimethoxyphenyl). All complexes tested were found to be active catalysts for transfer hydrogenation of ketones, with complex 4 displaying the highest activity. Complex 4 also exhibits moderate activity toward simple olefins and an aromatic nitro compound.

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