Unsymmetrical pnp-pincer type phosphaalkene ligands protected by a fused-ring bulky eind group: Synthesis and applications to rh(i) and ir(i) complexes

Hiro Omi Taguchi, Daichi Sasaki, Katsuhiko Takeuchi, Shota Tsujimoto, Tsukasa Matsuo, Hiromasa Tanaka, Kazunari Yoshizawa, Fumiyuki Ozawa

Research output: Contribution to journalArticle

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Abstract

We recently reported that 2-(phospholanylmethyl)-6-(2-phosphaethenyl)pyridine (PPEP) with a 2,4,6-tri-tert-butylphenyl group (Mes∗) as steric protection of the PC bond serves as a noninnocent ligand on Ir(I), leading to extremely high reactivity toward metal-ligand cooperative activation of ammonia and acetonitrile. The high reactivity is largely due to the strong accepting properties of the PC bond. However, PPEP had a stability problem that provokes the loss of the PC bond on other transition metals, including Rh(I), and restricts its utilization. This paper describes the synthesis of Eind-PPEP protected by an octaethyl-s-hydrindacen-4-yl group (Eind) instead of Mes∗. The fused-ring bulky Eind group successfully prevents the loss of the PC bond and enables us to compare the reactivity of Rh(I) and Ir(I) complexes toward ammonia. The complex K[RhCl(Eind-PPEP∗)], bearing a dearomatized Eind-PPEP∗ ligand, undergoes simple ligand displacement to give [Rh(NH3)(Eind-PPEP∗)], whereas the iridium analogue K[IrCl(Eind-PPEP∗)] causes N-H bond cleavage to form [Ir(NH2)(Eind-PPEP)]. DFT calculations indicate a thermodynamic cause of the metal-dependent product change.

Original languageEnglish
Pages (from-to)1526-1533
Number of pages8
JournalOrganometallics
Volume35
Issue number10
DOIs
Publication statusPublished - May 23 2016

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pyridines
Ligands
ligands
rings
synthesis
reactivity
Ammonia
ammonia
Bearings (structural)
Metals
Iridium
pyridine
causes
iridium
Discrete Fourier transforms
metals
acetonitrile
Transition metals
cleavage
Chemical activation

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

Cite this

Unsymmetrical pnp-pincer type phosphaalkene ligands protected by a fused-ring bulky eind group : Synthesis and applications to rh(i) and ir(i) complexes. / Taguchi, Hiro Omi; Sasaki, Daichi; Takeuchi, Katsuhiko; Tsujimoto, Shota; Matsuo, Tsukasa; Tanaka, Hiromasa; Yoshizawa, Kazunari; Ozawa, Fumiyuki.

In: Organometallics, Vol. 35, No. 10, 23.05.2016, p. 1526-1533.

Research output: Contribution to journalArticle

Taguchi, Hiro Omi ; Sasaki, Daichi ; Takeuchi, Katsuhiko ; Tsujimoto, Shota ; Matsuo, Tsukasa ; Tanaka, Hiromasa ; Yoshizawa, Kazunari ; Ozawa, Fumiyuki. / Unsymmetrical pnp-pincer type phosphaalkene ligands protected by a fused-ring bulky eind group : Synthesis and applications to rh(i) and ir(i) complexes. In: Organometallics. 2016 ; Vol. 35, No. 10. pp. 1526-1533.
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abstract = "We recently reported that 2-(phospholanylmethyl)-6-(2-phosphaethenyl)pyridine (PPEP) with a 2,4,6-tri-tert-butylphenyl group (Mes∗) as steric protection of the PC bond serves as a noninnocent ligand on Ir(I), leading to extremely high reactivity toward metal-ligand cooperative activation of ammonia and acetonitrile. The high reactivity is largely due to the strong accepting properties of the PC bond. However, PPEP had a stability problem that provokes the loss of the PC bond on other transition metals, including Rh(I), and restricts its utilization. This paper describes the synthesis of Eind-PPEP protected by an octaethyl-s-hydrindacen-4-yl group (Eind) instead of Mes∗. The fused-ring bulky Eind group successfully prevents the loss of the PC bond and enables us to compare the reactivity of Rh(I) and Ir(I) complexes toward ammonia. The complex K[RhCl(Eind-PPEP∗)], bearing a dearomatized Eind-PPEP∗ ligand, undergoes simple ligand displacement to give [Rh(NH3)(Eind-PPEP∗)], whereas the iridium analogue K[IrCl(Eind-PPEP∗)] causes N-H bond cleavage to form [Ir(NH2)(Eind-PPEP)]. DFT calculations indicate a thermodynamic cause of the metal-dependent product change.",
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