Decarbonylative ether dissection by iridium pincer complexes

Yoo, Changho; Dodge, Henry M.; Farquhar, Alexandra H.; Gardner, Kristen E.; Miller, Alexander J. M.

doi:10.1039/d0sc03736b

Cited by 10 publications

(13 citation statements)

References 51 publications

(83 reference statements)

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“…After complexation, a large amount of [Ir(ppy) 2 (di(2-pyridyl)ketone)] + was isolated in the reaction medium as side product. Despite we are not able to provide a mechanistic interpretation for such experimental evidence, actually the cleavage of the C–O ether bond by pincer iridium complexes has been previously reported in similar reaction conditions [ 34 , 35 ]. On the contrary, the ligand A4 reacts with [Ir(ppy) 2 Cl] 2 giving the stable corresponding complex [Ir(ppy) 2 ( A4 )] + .…”

Section: Resultsmentioning

confidence: 66%

Dipyridylmethane Ethers as Ligands for Luminescent Ir Complexes

et al. 2021

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This work reports two new cationic heteroleptic cyclometalated iridium complexes, containing ether derivatives of di(pyridin-2-yl)methanol. The new ligands are based on dipyridin-2-ylmethane and are designed to obtain ether-based intermediates with extended electronic conjugation by insertion of π system such as phenyl, allyl and ethynyl. Different synthetic strategies were employed to introduce these units, as molecular wires, between the dipyridin-2-ylmethane chelating portion and the terminal N-containing functional group, such as amine and carbamide. The corresponding complexes show luminescence in the blue region of the spectrum, lifetimes between 0.6 and 2.1 μs, high quantum yield and good electrochemical behavior. The computational description (DFT) of the electronic structure highlights the key role of the conjugated π systems on optical and electrochemical properties of the final products.

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Section: Resultsmentioning

confidence: 66%

Dipyridylmethane Ethers as Ligands for Luminescent Ir Complexes

et al. 2021

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“…The three ligands were prepared according to recently reported procedures. 17,18 The methoxy group in the backbone was selected to prevent unwanted metalation at the site ortho to the phosphinite (para to the amine donor). 11,19 Refluxing Pd(COD)Cl2 with the ligand produced square planar palladium(II) chloride complexes with tridentate NCOP pincer coordination.…”

Section: Resultsmentioning

confidence: 99%

Cation-Controlled Olefin Isomerization Catalysis with Palladium Pincer Complexes

Farquhar

Gardner

Acosta-Calle

et al. 2022

Preprint

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A series of palladium(II) pincer complexes with dif-ferent substituents on the amine donor has been prepared and studied in olefin isomerization cataly-sis. Installing a macrocycle into the pincer ligand enables cation-switchable positional olefin isomer-ization: no reaction is observed with the catalyst alone, while in the presence of Li+ salts isomeriza-tion proceeds cleanly. Mechanistic studies implicate a key role of highly electrophilic Pd centers with accessible olefin binding sites in catalysis.

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“…Initial studies investigating the activation of MeOAc by previously reported (NCOP)Ir(CO) complexes did not show promising reactivity, despite the ability of these carbonyl complexes to carry out the individual steps and overall catalytic reaction of methanol carbonylation in the presence of methyl iodide. , Inspired by reports from the Goldman group demonstrating net C–O bond activation via initial C–H bond activation, ,− and our own recent observation of ether decarbonylation via C–H bond activation, we turned to the dinitrogen complex [( MeO‑Et NCOP)Ir] 2 (μ-N 2 ) ( 1 ).…”

Section: Resultsmentioning

confidence: 99%

“…Although partial dissociation of the ligand was observed under catalytic conditions, stoichiometric studies established the viability of each reaction step, including Lewis acid promotion of the C–C bond-forming migratory insertion step . We recently isolated a NCOP iridium(I)–dinitrogen compound and found that it facilitates decarbonylative C–O bond cleavage of ethers, initiated by C–H bond activation . These results led us to a stepwise study of iodide-free methanol carbonylation using methyl acetate as the methylating reagent.…”

Section: Introductionmentioning

confidence: 97%

“…23 We recently isolated a NCOP iridium(I)−dinitrogen compound and found that it facilitates decarbonylative C−O bond cleavage of ethers, initiated by C−H bond activation. 24 These results led us to a stepwise study of iodide-free methanol carbonylation using methyl acetate as the methylating reagent. Here, the aminophenylphosphinite ligand supports clean formal oxidative addition of methyl acetate to generate an isolable methyliridium acetate complex.…”

Section: ■ Introductionmentioning

confidence: 99%

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Stepwise Iodide-Free Methanol Carbonylation via Methyl Acetate Activation by Pincer Iridium Complexes

Yoo

Miller

2021

J. Am. Chem. Soc.

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Iodide is an essential promoter in the industrial production of acetic acid via methanol carbonylation, but it also contributes to reactor corrosion and catalyst deactivation. Here we report that iridium pincer complexes mediate the individual steps of methanol carbonylation to methyl acetate in the absence of methyl iodide or iodide salts. Iodide-free methylation is achieved under mild conditions by an aminophenylphosphinite pincer iridium(I) dinitrogen complex through net C−O oxidative addition of methyl acetate to produce an isolable methyliridium-(III) acetate complex. Experimental and computational studies provide evidence for methylation via initial C−H bond activation followed by acetate migration, facilitated by amine hemilability. Subsequent CO insertion and reductive elimination in methanol solution produced methyl acetate and acetic acid. The net reaction is methanol carbonylation to acetic acid using methyl acetate as a promoter alongside conversion of an iridium dinitrogen complex to an iridium carbonyl complex. Kinetic studies of migratory insertion and reductive elimination reveal essential roles of the solvent methanol and distinct features of acetate and iodide anions that are relevant to the design of future catalysts for iodide-free carbonylation.

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Decarbonylative ether dissection by iridium pincer complexes

Abstract: A unique chain-rupturing transformation that converts an ether functionality into two hydrocarbyl units and carbon monoxide is reported, mediated by iridium(I) complexes supported by aminophenylphosphinite (NCOP) pincer ligands. The decarbonylation,...

Cited by 10 publications

References 51 publications

Dipyridylmethane Ethers as Ligands for Luminescent Ir Complexes

Dipyridylmethane Ethers as Ligands for Luminescent Ir Complexes

Cation-Controlled Olefin Isomerization Catalysis with Palladium Pincer Complexes

Stepwise Iodide-Free Methanol Carbonylation via Methyl Acetate Activation by Pincer Iridium Complexes

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