Synthesis and reactivity of an iridium(I) acetonyl PNP complex. Experimental and computational study of metal-ligand cooperation in H-H and C-H bond activation via reversible ligand dearomatization

Leonid Schwartsburd, Mark A. Iron, Leonid Konstantinovski, Yael Diskin-Posner, Gregory Leitus, Linda J.W. Shimon, David Milstein

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Abstract

The complex (PNP)IrI(CH2COCH3) 2 (PNP = 2,6-bis((di-tert-butylphosphino)methyl)pyridine) was prepared by reaction of the dearomatized, electron-rich complex (PNP)IrI(COE) (1; PNP* = deprotonated PNP, COE = cyclooctene) with acetone. Upon treatment with CO, complex 2 undergoes a surprising elimination of acetone to form the dearomatized species (PNP)IrI(CO) (4), involving proton migration from the ligand "arm" to the acetonyl moiety. DFT studies reveal that this process occurs via the square-pyramidal intermediate 2+CO, formed upon CO coordination to 2, in which the acetonyl moiety is located at the apical position prior to proton migration. Reaction of 2 with H2 (D2) indicates an equilibrium between complex 2 and the nonaromatic (PNP)IrIII(H) (CH2COCH3) complex 2b, which is the species that actually activates H2 to exclusively form the trans-dihydride (PNP)Ir III(H)2(CH2COCH3) (5a) and activates D2 to form the trans-hydride-deuteride 5b with benzylic-D incorporation, as also corroborated by DFT studies. Interestingly, benzene C-H activation by complex 2 results in formation of the complex (PNP)Ir I(C6H5) (6a) and elimination of acetone. DFT studies show that the benzene C-H bond is actually activated by the dearomatized "bare" (PNP)IrI intermediate 2c, formed upon acetone elimination from 2.

Original languageEnglish
Pages (from-to)3817-3827
Number of pages11
JournalOrganometallics
Volume29
Issue number17
DOIs
Publication statusPublished - Sep 13 2010

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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