Water-Accelerated Decomposition of Olefin Metathesis Catalysts

Blanco, Christian O.; Fogg, Deryn E.

doi:10.1021/acscatal.2c05573

Cited by 14 publications

(10 citation statements)

References 75 publications

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“…The challenges of combining both catalysts in one pot and simultaneously avoiding mutual deactivation were (i) the chloride concentration and (ii) the addition of hydrogen gas. Chloride is an essential ligand for the Grubbs–Hoveyda-type catalysts, especially in aqueous media. ,, However, chloride ion deactivated the Rh-based catalyst by blocking coordination sites for the substrate. Therefore, a delicate balance needed to be found.…”

Section: Fhua As a Protein Scaffold For Metal Catalystsmentioning

confidence: 99%

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FhuA: From Iron-Transporting Transmembrane Protein to Versatile Scaffolds through Protein Engineering

et al. 2023

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Metrics & MoreArticle Recommendations CONSPECTUS: Protein engineering has emerged as a powerful methodology to tailor the properties of proteins. It empowers the design of biohybrid catalysts and materials, thereby enabling the convergence of materials science, chemistry, and medicine. The choice of a protein scaffold is an important factor for performance and potential applications. In the past two decades, we utilized the ferric hydroxamate uptake protein FhuA. FhuA is, from our point of view, a versatile scaffold due to its comparably large cavity and robustness toward temperature as well as organic cosolvents. FhuA is a natural iron transporter located in the outer membrane of Escherichia coli (E. coli). Wild-type FhuA consists of 714 amino acids and has a β-barrel structure composed of 22 antiparallel β-sheets, closed by an internal globular "cork" domain (amino acids 1−160). FhuA is robust in a broad pH range and toward organic cosolvents; therefore, we envisioned FhuA to be a suitable platform for various applications in (i) biocatalysis, (ii) materials science, and (iii) the construction of artificial metalloenzymes.(i) Applications in biocatalysis were achieved by removing the globular cork domain (FhuA_Δ1−160), thereby creating a large pore for the passive transport of otherwise difficult-to-import molecules through diffusion. Introducing this FhuA variant into the outer membrane of E. coli facilitates the uptake of substrates for downstream biocatalytic conversion. Furthermore, removing the globular "cork" domain without structural collapse of the ß-barrel protein allowed the use of FhuA as a membrane filter, exhibiting a preference for D-arginine over L-arginine.(ii) FhuA is a transmembrane protein, which makes it attractive to be used for applications in non-natural polymeric membranes. Inserting FhuA into polymer vesicles yielded so-called synthosomes (i.e., catalytic synthetic vesicles in which the transmembrane protein acted as a switchable gate or filter). Our work in this direction enables polymersomes to be used in biocatalysis, DNA recovery, and the controlled (triggered) release of molecules. Furthermore, FhuA can be used as a building block to create protein− polymer conjugates to generate membranes.(iii) Artificial metalloenzymes (ArMs) are formed by incorporating a non-native metal ion or metal complex into a protein. This combines the best of two worlds: the vast reaction and substrate scope of chemocatalysis and the selectivity and evolvability of enzymes. With its large inner diameter, FhuA can harbor (bulky) metal catalysts. Among others, we covalently attached a Grubbs− Hoveyda-type catalyst for olefin metathesis to FhuA. This artificial metathease was then used in various chemical transformations, ranging from polymerizations (ring-opening metathesis polymerization) to enzymatic cascades involving cross-metathesis.Ultimately, we generated a catalytically active membrane by copolymerizing FhuA and pyrrole. The resulting biohybrid material was then equipped with the Grubbs−Hoveyda-type...

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Section: Fhua As a Protein Scaffold For Metal Catalystsmentioning

confidence: 99%

“…Chloride is an essential ligand for the Grubbs−Hoveyda-type catalysts, especially in aqueous media. 34,39,40 However, chloride ion deactivated the Rh-based catalyst by blocking coordination sites for the substrate. Therefore, a delicate balance needed to be found.…”

Section: Fhua As a Protein Scaffold For Metal Catalystsmentioning

confidence: 99%

FhuA: From Iron-Transporting Transmembrane Protein to Versatile Scaffolds through Protein Engineering

et al. 2023

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“…Several studies have examined the tolerance of HG-II derivatives to protic solvent molecules (such as methanol and water) for bio-related applications of OM and have proposed several decomposition pathways. [38][39][40][41][42][43][44][45][46] One mechanism is based on the replacement of the chlorido ligands with a protic ligand such as water, 44 while the other pathways involve the coordination of protic molecules to an open site generated in a catalytic cycle. 39,40,45,46 In this context, we hypothesized that 11 -S should exhibit high tolerance to protic molecules because the sulfur-containing benzylidene ligand is expected to protect the metal center through the S-coordination during the catalytic cycle.…”

Section: Effects Of Protic Solvents On the Om Activity Of Ruthenium C...mentioning

confidence: 99%

Reactivity regulation for olefin metathesis-catalyzing ruthenium complexes with sulfur atoms at the terminal of 2-alkoxybenzylidene ligands

Kinugawa,

Matsuo

2023

Dalton Trans.

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“…This leading position is now being contested by new ruthenium catalysts stabilized by cyclic (alkyl)(amino) carbene (CAAC) ligands. , The CAAC catalysts have enabled breakthrough performance in topical current applications of olefin metathesis, including the synthesis of macrocycles via ring-closing metathesis (mRCM), , and the transformation of renewable internal olefins into 1-olefins via cross-metathesis with ethylene (“ethenolysis”). − Catalysts bearing the phenyl-protected C1 Ph ligand (Chart ) stand out for their resistance to degradation by nucleophiles or Bronsted base, water, , and unidentified contaminants in technical-grade ethylene, while a C2 Me derivative enabled TONs up to 340,000 in ethenolysis with ultra-high-purity ethylene at 1 ppm catalyst . All, however, are highly sensitive to catalyst concentration. ,,− Indeed, a ca.…”

Section: Introductionmentioning

confidence: 99%

Mesomeric Acceleration Counters Slow Initiation of Ruthenium–CAAC Catalysts for Olefin Metathesis (CAAC = Cyclic (Alkyl)(Amino) Carbene)

Occhipinti

Boisvert

et al. 2023

ACS Catal.

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Ruthenium catalysts bearing cyclic (alkyl)(amino)carbene (CAAC) ligands can attain very high productivities in olefin metathesis, owing to their resistance to unimolecular decomposition. Because the propagating methylidene species RuCl2(CAAC)(CH2) is extremely susceptible to bimolecular decomposition, however, turnover numbers in the metathesis of terminal olefins are highly sensitive to catalyst concentration, and hence loadings. Understanding how, why, and how rapidly the CAAC complexes partition between the precatalyst and the active species is thus critical. Examined in a dual experimental–computational study are the rates and basis of initiation for phosphine-free catalysts containing the leading CAAC ligand C1 Ph , in which a CMePh group α to the carbene carbon helps retard degradation. The Hoveyda-class complex HC1 Ph (RuCl2(L)(CHAr), where L = C1 Ph , Ar = C6H3-2-O i Pr-5-R; R = H) is compared with its nitro-Grela analogue (nG-C1 Ph ; R = NO2) and the classic Hoveyda catalyst HII (L = H2IMes; R = H). t-Butyl vinyl ether (tBuVE) was employed as substrate, to probe the reactivity of these catalysts toward olefins of realistic bulk. Initiation is ca. 100× slower for HC1 Ph than HII in C6D6, or 44× slower in CDCl3. The rate-limiting step for the CAAC catalyst is cycloaddition; for HII, it is tBuVE binding. Initiation is 10–13× faster for nG-C1 Ph than HC1 Ph in either solvent. DFT analysis reveals that this rate acceleration originates in an overlooked role of the nitro group. Rather than weakening the Ru–ether bond, as widely presumed, the NO2 group accelerates the ensuing, rate-limiting cycloaddition step. Faster reaction is caused by long-range mesomeric effects that modulate key bond orders and Ru-ligand distances, and thereby reduce the trans effect between the carbene and the trans-bound alkene in the transition state for cycloaddition. Mesomeric acceleration may plausibly be introduced via any of the ligands present, and hence offers a powerful, tunable control element for catalyst design.

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Water-Accelerated Decomposition of Olefin Metathesis Catalysts

Cited by 14 publications

References 75 publications

FhuA: From Iron-Transporting Transmembrane Protein to Versatile Scaffolds through Protein Engineering

FhuA: From Iron-Transporting Transmembrane Protein to Versatile Scaffolds through Protein Engineering

Reactivity regulation for olefin metathesis-catalyzing ruthenium complexes with sulfur atoms at the terminal of 2-alkoxybenzylidene ligands

Mesomeric Acceleration Counters Slow Initiation of Ruthenium–CAAC Catalysts for Olefin Metathesis (CAAC = Cyclic (Alkyl)(Amino) Carbene)

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