Advanced Synthesis & Catalysis· 2026Q1
Influence of the Size of the Metallacycle of P‐NHC Mn Complexes for the Hydrogenation of Esters
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- Q1SCImago
- 2026year
Short summary
A manganese complex with a seven-membered chelate ring ([Mn-5 Mes] C7) shows significantly higher activity in ester hydrogenation compared to analogs with five- and six-membered rings.
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Key points
- A seven-membered chelate ring manganese complex ([Mn-5 Mes] C7) is more active for ester hydrogenation than five- and six-membered ring analogs.
- The [Mn-5 Mes] C7 complex achieved quantitative yields for various esters, including halogenated and poly(ε-caprolactone), using 0.25 mol% catalyst loading.
- Structural analysis shows larger rings increase the metal's electron donation and reduce steric strain, explaining enhanced catalytic activity.
- Methods used for characterization include X-ray crystallography, NMR, IR, and cyclic voltammetry.
AI-generated from the title and abstract; the full text is not read.
Abstract
Chelate ring size is a key but underexplored parameter in the design of manganese‐based hydrogenation catalysts. Here, we report the synthesis and characterization of Mn(I) NHC–phosphine complexes [Mn‐5] C7 featuring a seven‐membered chelate ring and their application to the hydrogenation of carboxylic esters. The N‐mesityl‐substituted complex [Mn‐5 Mes ] C7 , with markedly improved activity relative to its five‐ and six‐membered analogs, achieves quantitative yields of the corresponding alcohols (0.25 mol%, 2.5 mol% KHBEt 3 , 50 bar H 2 , 2‐MeTHF, 100–120 °C, 5 h), including halogenated aromatic esters, aliphatic esters, and poly(ε‐caprolactone), which is fully depolymerized to hexan‐1‐ol. Systematic comparison of the C5, C6, and C7 series by X‐ray crystallography, multinuclear NMR, IR, and cyclic voltammetry shows that ring enlargement progressively increases the bite angle, reduces steric strain, and enhances electron donation at the metal, structural and electronic changes that collectively account for the improved catalytic performance.
The authors' abstract, as published at the source. Advanced Synthesis & Catalysis, 2026 · DOI ↗
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Field: Inorganic Chemistry
Inorganic ChemistryChemistry