918344-68-0Relevant academic research and scientific papers
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
Schwartsburd, Leonid,Iron, Mark A.,Konstantinovski, Leonid,Diskin-Posner, Yael,Leitus, Gregory,Shimon, Linda J. W.,Milstein, David
, p. 3817 - 3827 (2010/12/24)
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.
Metal-ligand cooperation in C-H and H2 activation by an electron-rich PNP Ir(I) system: Facile ligand dearomatization-aromatization as key steps
Ben-Ari, Eyal,Leitus, Gregory,Shimon, Linda J. W.,Milstein, David
, p. 15390 - 15391 (2007/10/03)
Unusual reactions are reported, in which the aromatic PNP ligand (PNP = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine) acts in concert with the metal in the activation of H2 and benzene, via facile aromatization/dearomatization processes of the ligand. A new, dearomatized electron-rich (PNP*)Ir(I) complex 2 (PNP* = deprotonated PNP) activates benzene to form the aromatic (PNP)Ir(I)Ph 4, which upon treatment with CO undergoes a surprising oxidation process to form (PNP*)Ir(III)(H)CO 6, involving proton migration from the ligand "arm" to the metal, with concomitant dearomatization. 4 undergoes stereoselective activation of H2 to exclusively form the trans-dihydride 7, rather than the expected cis-dihydride complex. Our evidence, including D-labeling, suggests the possibility that the Ir(I)-Ph complex is transformed to the dearomatized Ir(III)(Ph)(H) (independently prepared at low temperature), which may be the actual intermediate undergoing H2 activation. Copyright
