Impact of the Methylene Bridge Substitution in Chelating NHC‐Phosphine Mn(I) Catalyst for Ketone Hydrogenation

Chemistry - A European Journal, Journal Year: 2024, Volume and Issue: 30(22)

Published: Feb. 7, 2024

Abstract Systematic modification of the chelating NHC‐phosphine ligand (NHC = N ‐heterocyclic carbene) in highly efficient ketone hydrogenation Mn(I) catalyst fac ‐[(Ph 2 PCH NHC)Mn(CO) 3 Br] has been performed and catalytic activity resulting complexes was evaluated using acetophenone as a benchmark substrate. While variation phosphine NHC moieties led to inferior results than for parent system, incorporation phenyl substituent into methylene bridge improved performance by ca . times providing maximal TON values range 15000–20000. Mechanistic investigation combining experimental computational studies allowed rationalize this beneficial effect an enhanced stabilization reaction intermediates including anionic hydride species PC(Ph)NHC)Mn(CO) H] − playing crucial role process. These highlight interest such carbon substitution strategy being rarely employed design chemically non‐innocent ligands.

Language: Английский

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Hydrogenation and Cross-Coupling Reactions Catalyzed by Mn, Fe, and Co Aromatic Pincer Complexes

Organometallics, Journal Year: 2023, Volume and Issue: 42(18), P. 2426 - 2446

Published: Sept. 8, 2023

Currently, the development of environmentally benign and effective catalytic reactions for organic synthesis based on low-cost abundant metals is one central research goals in modern chemistry. This review covers advancements homogeneously catalyzed using pincer complexes manganese, iron, cobalt featuring aryl pyridine backbones. Specifically, C–C coupling hydrogenation alkenes, alkynes, aldehydes, ketones, esters, nitriles, CO2, carbamates, ureas, cyclic imides azo compounds are described, including their scope mechanistic insights. Overall, this emphasizes that combination inexpensive readily available metals, such as Mn, Fe, Co, with ligands capable ligand–metal cooperation may lead to creation innovative, versatile, catalysts, some which can even exceed activity state-of-the-art noble-metal systems green chemistry processes.

Language: Английский

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Meta-Xylene-Based Diamines with Protected Benzyl Sites: Potential NCN Pincer Ligands with Tunable Steric Profiles

Molecules, Journal Year: 2025, Volume and Issue: 30(6), P. 1331 - 1331

Published: March 16, 2025

Bulky NCN aryl-diamides featuring methyl groups in the benzyl positions were synthesized with aim of creating a new class meta-xylene-based trianionic pincer ligands where common decomposition pathway metal complexes via C-H activation is prevented. Sterically demanding substituents on furthermore provide steric protection centre and can help prevent dimerization complexes. While double deprotonation formation dilithium salt was straightforward, difficulties encountered when attempting to deprotonate ipso-CH proton central aryl ring yield ligands. This stands contrast related without benzylic positions. Experimental theoretical investigations led conclusion that challenges third are likely caused by an interplay increased electron density at nitrogen atoms hindrance. Both effects originate introduction positions, which make targeted less accessible. These results further insight into impact both electronic properties ligands, may find utility coordination chemistry applications metalation be achieved direct rather than requiring triple deprotonation.

Language: Английский

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Renaissance in Alkyne Semihydrogenation: Mechanism, Selectivity, Functional Group Tolerance, and Applications in Organic Synthesis

Chemical Reviews, Journal Year: 2025, Volume and Issue: unknown

Published: April 25, 2025

Alkenes constitute a significant class of chemical compounds with applications in the bulk, pharmaceutical, or perfume industry. Among known methods olefin production, semihydrogenation C-C triple bond seems to be most straightforward one. Nonetheless, success this reaction requires full control over diastereoselectivity, eradication parasitic process over-reduction migration double formed, and achieving satisfactory functional-group compatibility. The review demonstrates developments field alkyne period 2010-2022, selected papers published 2023 2024, emphasizing solutions above-mentioned limitations. We discuss mechanistic aspects transformation, including those related unconventional systems. includes examples organic synthesis, confirming considerable utility process. Finally, strategies enhance catalyst selectivity are summarized. For reader's convenience, we provided graphical guidebook catalytic systems, illustrating efficiency particular method.

Language: Английский

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Earth-abundant Ni-Zn nanocrystals for efficient alkyne semihydrogenation catalysis

Nature Communications, Journal Year: 2025, Volume and Issue: 16(1)

Published: May 12, 2025

Abstract The development of catalysts that are based on earth-abundant metals remains a grand challenge. Alloy nanocrystals (NCs) form an emerging class heterogeneous catalysts, offering the promise small, uniform with composition-control. Here, we report synthesis small Ni and bimetallic Ni-X (X= Zn, Ga, In) NCs for alkyne semihydrogenation catalysis. We show 3 Zn particularly reactive selective under mild reaction conditions at low loadings. While all more than pure NCs, Ni-Zn also maintain excellent reactivity compared to Ni-Ga Ni-In alloys. Ab-initio calculations can explain differences in reactivity, indicating that, unlike Ga In, atoms interact substrates. further robust tolerate broad range substrates, which may be linked favorable amine-terminated surface.

Language: Английский

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Selective Transfer Semihydrogenation of Alkynes Catalyzed by an Iron PCP Pincer Alkyl Complex

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(21), P. 14012 - 14022

Published: Oct. 17, 2023

Two bench-stable Fe(II) alkyl complexes [Fe(κ3PCP-PCP-iPr)(CO)2(R)] (R = CH2CH2CH3, CH3) were obtained by the treatment of [Fe(κ3PCP-PCP-iPr)(CO)2(H)] with NaNH2 and subsequent addition CH3CH2CH2Br CH3I, respectively. The reaction proceeds via anionic Fe(0) intermediate Na[Fe(κ3PCP-PCP-iPr)(CO)2]. catalytic performance both was investigated for transfer hydrogenation terminal internal alkynes utilizing PhSiH3 iPrOH as a hydrogen source. Precatalyst activation is initiated migration ligand to carbonyl C atom an adjacent CO ligand. In agreement previous findings, rate follows order nPr > Me. Accordingly, [Fe(κ3PCP-PCP-iPr)(CO)2(CH2CH2CH3)] more active catalyst. takes place at 25 °C catalyst loading 0.5 mol%. There no overhydrogenation, in case alkynes, exclusively, Z-alkenes are formed. implemented protocol tolerates variety electron-donating electron-withdrawing functional groups including halides, nitriles, unprotected amines, heterocycles. Mechanistic investigations deuterium labeling studies DFT calculations undertaken provide reasonable mechanism.

Language: Английский

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Transfer semi-hydrogenation of terminal alkynes with a well-defined iron complex

Dalton Transactions, Journal Year: 2024, Volume and Issue: 53(8), P. 3484 - 3489

Published: Jan. 1, 2024

A bench stable iron( ii ) complex with the pincer ligand backbone was synthesized and characterized. The well-defined iron successfully utilized for dehydrogenation of DMAB subsequent transfer semi-hydrogenation terminal alkynes.

Language: Английский

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Mechanistic Studies and Identification of Catalyst Deactivation Pathways for Pyridine(diimine) Iron Catalyzed C(sp²)–H Borylation

ACS Catalysis, Journal Year: 2024, Volume and Issue: 14(18), P. 13999 - 14011

Published: Sept. 6, 2024

The synthesis and application of aryl-substituted pyridine(diimine) iron complexes (

Language: Английский

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PNP‐Pincer Ligands Armed With Methyls: New Tools To Control Sterics and Non‐Innocence

ChemCatChem, Journal Year: 2023, Volume and Issue: 15(20)

Published: Sept. 1, 2023

Abstract The widespread use of pyridine‐based PNP pincer ligands has inspired the concept metal‐ligand cooperation (MLC), in which reactivity at deprotonated CH 2 (or NH) arm ligand is proposed to play an important role. Several groups developed a family PNP‐type with methylated arms were initially introduced test effect blocking MLC catalysis, but eventually led unexpected consequences such as stabilization unusual oxidation states, beneficial catalytic activity, or selectivity. Analysis sterics imposed by introducing Me revealed that protection can be efficient tool control around metal alternative phosphine substitution, leading much greater steric hinderance above and below pincer's coordination plane. This Concept will describe several illustrative examples contrast classical /NH‐arm pincers their CMe /NMe‐armed counterparts, particular related Ru‐catalyzed alcohol dehydrogenative coupling, Fe‐catalyzed hydrogenation, hydroboration, alkyne semihydrogenation.

Language: Английский

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Selective Catalysts for the Homogeneous Semi‐Hydrogenation

Advanced Synthesis & Catalysis, Journal Year: 2023, Volume and Issue: 365(24), P. 4538 - 4543

Published: Sept. 5, 2023

Abstract An efficient and highly selective semi‐hydrogenation of terminal alkynes to alkenes using neutral dimeric rhodium(I) complexes the type [Rh( μ ‐Cl)(PP)] 2 is presented. Dehydroisophytol (DIP) was chosen as alkyne for this study because its high importance in industrial production synthetic vitamin E. Excellent selectivity over 91% towards alkene achieved with known new rhodium catalysts. No deactivation observed molar Rh:DIP ratio could be increased 1:20 000, importantly, no reduction observed. The results presented open door application homogeneous alkynes.

Language: Английский

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