A dearomatized anionic PNP pincer rhodium complex

C-H and H-H bond activation by metal-ligand cooperation and inhibition by dinitrogen

Leonid Schwartsburd, Mark A. Iron, Leonid Konstantinovski, Eyal Ben-Ari, David Milstein

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

The anionic dearomatized complex [(PNP*)RhICl]K (2; PNP = 2,6-bis((di-tert-butylphosphino)methyl)pyridine, PNP* = deprotonated PNP) was prepared by reaction of the aromatic (PNP)RhICl complex 1 with KN(SiMe3)2 in dry benzene. Spectroscopic characterization and DFT calculations confirm a nonaromatic square-planar structure of complex 2. Under an atmosphere of dry argon, 2 undergoes facile C-H activation of benzene by cooperation between the metal center and the pincer ligand, with aromatization of the ligand, to form the complex (PNP)RhI(C 6H5) (3a). This reaction is inhibited by dinitrogen, which reacts with 2 to form the complex (PNP*)RhI(N2) (4), indicating higher stabilization of the 14-electron (PNP*)Rh I species 5 by dinitrogen as compared with chloride. Similarly, treatment of 2 with CO results in KCl liberation to form the dearomatized (PNP*)RhICO (8). In a protic environment, the dearomatized complex 2 is quickly reprotonated to regenerate the aromatic starting complex 1. Upon treatment with MeI, 2 undergoes oxidative addition to form the nonaromatic (PNP*)RhIII(CH3)Cl (10), while the dearomatized ligand remains intact. Complex 2 undergoes facile activation of H2 to form the monohydride (PNP)RhI(H) (11a) and with D2 to form (PNP)RhI(D) (11b) with benzylic-D incorporation, via metal-ligand cooperation by aromatization of the ligand. The reactivity of 2 with H2 is significantly higher than that of 4.

Original languageEnglish
Pages (from-to)2721-2729
Number of pages9
JournalOrganometallics
Volume30
Issue number10
DOIs
Publication statusPublished - May 23 2011

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Rhodium
rhodium
Metals
Chemical activation
activation
Ligands
ligands
Aromatization
metals
Benzene
benzene
Argon
planar structures
Carbon Monoxide
Discrete Fourier transforms
Chlorides
pyridines
reactivity
Stabilization
stabilization

ASJC Scopus subject areas

  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

Cite this

A dearomatized anionic PNP pincer rhodium complex : C-H and H-H bond activation by metal-ligand cooperation and inhibition by dinitrogen. / Schwartsburd, Leonid; Iron, Mark A.; Konstantinovski, Leonid; Ben-Ari, Eyal; Milstein, David.

In: Organometallics, Vol. 30, No. 10, 23.05.2011, p. 2721-2729.

Research output: Contribution to journalArticle

Schwartsburd, Leonid ; Iron, Mark A. ; Konstantinovski, Leonid ; Ben-Ari, Eyal ; Milstein, David. / A dearomatized anionic PNP pincer rhodium complex : C-H and H-H bond activation by metal-ligand cooperation and inhibition by dinitrogen. In: Organometallics. 2011 ; Vol. 30, No. 10. pp. 2721-2729.
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abstract = "The anionic dearomatized complex [(PNP*)RhICl]K (2; PNP = 2,6-bis((di-tert-butylphosphino)methyl)pyridine, PNP* = deprotonated PNP) was prepared by reaction of the aromatic (PNP)RhICl complex 1 with KN(SiMe3)2 in dry benzene. Spectroscopic characterization and DFT calculations confirm a nonaromatic square-planar structure of complex 2. Under an atmosphere of dry argon, 2 undergoes facile C-H activation of benzene by cooperation between the metal center and the pincer ligand, with aromatization of the ligand, to form the complex (PNP)RhI(C 6H5) (3a). This reaction is inhibited by dinitrogen, which reacts with 2 to form the complex (PNP*)RhI(N2) (4), indicating higher stabilization of the 14-electron (PNP*)Rh I species 5 by dinitrogen as compared with chloride. Similarly, treatment of 2 with CO results in KCl liberation to form the dearomatized (PNP*)RhICO (8). In a protic environment, the dearomatized complex 2 is quickly reprotonated to regenerate the aromatic starting complex 1. Upon treatment with MeI, 2 undergoes oxidative addition to form the nonaromatic (PNP*)RhIII(CH3)Cl (10), while the dearomatized ligand remains intact. Complex 2 undergoes facile activation of H2 to form the monohydride (PNP)RhI(H) (11a) and with D2 to form (PNP)RhI(D) (11b) with benzylic-D incorporation, via metal-ligand cooperation by aromatization of the ligand. The reactivity of 2 with H2 is significantly higher than that of 4.",
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AB - The anionic dearomatized complex [(PNP*)RhICl]K (2; PNP = 2,6-bis((di-tert-butylphosphino)methyl)pyridine, PNP* = deprotonated PNP) was prepared by reaction of the aromatic (PNP)RhICl complex 1 with KN(SiMe3)2 in dry benzene. Spectroscopic characterization and DFT calculations confirm a nonaromatic square-planar structure of complex 2. Under an atmosphere of dry argon, 2 undergoes facile C-H activation of benzene by cooperation between the metal center and the pincer ligand, with aromatization of the ligand, to form the complex (PNP)RhI(C 6H5) (3a). This reaction is inhibited by dinitrogen, which reacts with 2 to form the complex (PNP*)RhI(N2) (4), indicating higher stabilization of the 14-electron (PNP*)Rh I species 5 by dinitrogen as compared with chloride. Similarly, treatment of 2 with CO results in KCl liberation to form the dearomatized (PNP*)RhICO (8). In a protic environment, the dearomatized complex 2 is quickly reprotonated to regenerate the aromatic starting complex 1. Upon treatment with MeI, 2 undergoes oxidative addition to form the nonaromatic (PNP*)RhIII(CH3)Cl (10), while the dearomatized ligand remains intact. Complex 2 undergoes facile activation of H2 to form the monohydride (PNP)RhI(H) (11a) and with D2 to form (PNP)RhI(D) (11b) with benzylic-D incorporation, via metal-ligand cooperation by aromatization of the ligand. The reactivity of 2 with H2 is significantly higher than that of 4.

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