Salt-promoted catalytic methanol carbonylation using iridium pincer-crown ether complexes

Gregor, Lauren C.; Grajeda, Javier; White, Peter S.; Vetter, Andrew J.; Miller, Alexander J. M.

doi:10.1039/c8cy00328a

Cited by 27 publications

(21 citation statements)

References 36 publications

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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%

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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Section: Resultsmentioning

confidence: 99%

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

Yoo

Miller

2021

J. Am. Chem. Soc.

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“…30 ppm upeld shi of the phosphinite resonance relative to 1 18c6 (from d 143.67 to d 171.32) in the 31 P NMR spectrum provided an early indication that the product was an iridium(I) complex. 13,18 We initially vetted the spectroscopic data against the possibility of iridium(I) complexes with either (a) a tetradentate pincer-crown ether ligand containing one crown ether oxygen bound, (k 4 -MeO-18c6 NCOP)Ir, or (b) a tridentate pincer-crown ether ligand with N 2 completing the square planar coordination sphere, (k 3 -MeO-18c6 NCOP)Ir(N 2 ). However, neither of these structures could be explained by the NMR data.…”

Section: Intramolecular Ether Decarbonylationmentioning

confidence: 99%

“…1D). The new triplet and singlet were assigned as unexpected -OCH 2 CH 3 and -NCH 3 groups, respectively, using a combination of multidimensional NMR experiments, including 1 H-1 H COSY, 1 H- 13 C HSQC and 1 H- 13 C HMBC ( Fig. S42-S44, ESI †).…”

Section: Intramolecular Ether Decarbonylationmentioning

confidence: 99%

Decarbonylative ether dissection by iridium pincer complexes

et al. 2020

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“…In the course of this study, we found that adding a methoxy group to the phenyl backbone blocks C-H bond activation pathways that lead to catalyst deactivation. 39,40 Structural comparisons of catalysts with and without "blocking" methoxy groups were therefore sought ( Figure 2). The known hydrido chloride complex with the backbone methoxy group, k 4 -( MeO-18c6 NCOP iPr )Ir(H)(Cl) (1-18c6b), 38 was converted to aqua complex [k 4 -( MeO-18c6 NCOP iPr )Ir(H)(OH2)][BAr F 4] (3-18c6b) and then the desired catalyst [k 5 -( MeO-18c6 NCOP iPr )Ir(H)][BAr F 4] according to Figure 2.…”

Section: Synthesis Of New Catalysts Featuring Aza-18-crown-6mentioning

confidence: 99%

Selecting Double Bond Positions with a Single Cation- Responsive Iridium Olefin Isomerization Catalyst

Camp¹,

Kita²,

Blackburn³

et al. 2020

Preprint

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<div><div><div><p>The catalytic transposition of double bonds holds promise as an ideal route to alkenes with value as fragrances, commodity chemicals, and pharmaceuticals; yet, selective access to specific isomers is a challenge, requiring independent development of different catalysts for different products. In this work, a single cation-responsive iridium catalyst is developed for the selective production of either of two different internal alkene isomers. In the absence of salts, a single positional isomerization of 1-butene derivatives furnishes 2-alkenes with exceptional regioselectivity and stereoselectivity. The same catalyst, in the presence of Na+, mediates two positional isomerizations to produce 3-alkenes. The synthesis of new iridium pincer-crown ether catalysts based on an aza-18-crown-6 ether proved instrumental in achieving cation-controlled selectivity. Experimental and computational studies guided the development of a mechanistic model that explains the observed selectivity for various functionalized 1-butenes, providing insight into strategies for catalyst development based on non-covalent modifications.</p></div></div></div>

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Salt-promoted catalytic methanol carbonylation using iridium pincer-crown ether complexes

Abstract: Iridium complexes of pincer ligands containing aza-crown ether macrocycles are precatalysts for methanol carbonylation. Turnover numbers for all acetyl-containing products could be tuned from 265 to 1950 using metal and tetrabutylammonium salts.

Cited by 27 publications

References 36 publications

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

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

Decarbonylative ether dissection by iridium pincer complexes

Selecting Double Bond Positions with a Single Cation- Responsive Iridium Olefin Isomerization Catalyst

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