Gas‐Phase Models for the Nickel‐ and Palladium‐Catalyzed Deoxygenation of Fatty Acids
| Autor: | Victoria Pho, Richard A. J. O'Hair, Anastasios Polyzos, Victor Ryzhov, Allan J. Canty, Geethika K. Weragoda, Kevin Parker |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
chemistry.chemical_classification
Agostic interaction 010405 organic chemistry Carboxylic acid Phenanthroline Organic Chemistry Homogeneous catalysis 010402 general chemistry 01 natural sciences Medicinal chemistry Catalysis 0104 chemical sciences Inorganic Chemistry chemistry.chemical_compound chemistry Organopalladium Carboxylate Physical and Theoretical Chemistry Deoxygenation |
| Zdroj: | ChemCatChem. 12:5476-5485 |
| ISSN: | 1867-3899 1867-3880 |
| Popis: | Using fatty acids as renewable sources of biofuels requires deoxygenation. While a number of promising catalysts have been developed to achieve this, their operating mechanisms are poorly understood. Here, model molecular systems are studied in the gas phase using mass spectrometry experiments and DFT calculations. The coordinated metal complexes [(phen)M(O2CR)]+ (where phen=1,10‐phenanthroline; M=Ni or Pd; R=CnH2n+1, n≥2) are formed via electrospray ionization. Their collision‐induced dissociation (CID) initiates deoxygenation via loss of CO2 and [C,H2,O2]. The CID spectrum of the stearate complexes (R=C17H35) also shows a series of cations [(phen)M(R’)]+ (where R’ 17) separated by 14 Da (CH2) corresponding to losses of C2H4‐C16H32 (cracking products). Sequential CID of [(phen)M(R’)]+ ultimately leads to [(phen)M(H)]+ and [(phen)M(CH3)]+, both of which react with volatile carboxylic acids, RCO2H, (acetic, propionic, and butyric) to reform the coordinated carboxylate complexes [(phen)M(O2CR)]+. In contrast, cracking products with longer carbon chains, [(phen)M(R)]+ (R>C2), were unreactive towards these carboxylic acids. DFT calculations are consistent with these results and reveal that the approach of the carboxylic acid to the “free” coordination site is blocked by agostic interactions for R > CH3. |
| Databáze: | OpenAIRE |
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