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ArticleSize-Controlled Synthesis of Rhodium Nanocatalysts and Applications in Low-Temperature HydroformylationAndrew Lamkins 1,2, Charles J. Ward 1,2, Jeffrey T. Miller 3, Ziad Alsudairy 4, Xinle Li 4, Joseph Thuma 1,2, Ruoyu Cui 1,2, Xun Wu 1,2, Levi M. Stanley 1 and Wenyu Huang 1,2,*1 Department of Chemistry, Iowa State University, Ames, IA 50010, USA2 Ames Laboratory, U.S. Department of Energy, Ames, IA 50010, USA3 Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, USA4 Department of Chemistry, Clark Atlanta University, Atlanta, GA 30314, USA* Correspondence: whuang@iastate.eduReceived: 3 December 2024; Revised: 30 December 2024; Accepted: 3 January 2025; Published: 10 January 2025 Abstract: Controlling the size and distribution of metal nanoparticles is one of the simplest methods of tuning the catalytic properties of a material. For a nanocrystal particle, the ratio of edge-to-terrace sites can be critical in determining its catalytic activity and selectivity to desired products. To study these effects, we have developed a simple impregnation method of controlling the dispersion of rhodium atoms at the same metal loading in the range of nanoparticles less than 10 nm. Rh precursor salts are loaded onto inert SBA-15, and increasing the ratio of chloride to acetylacetonate salts improves the dispersion of rhodium atoms to form small Rh nanoparticles. Extensive characterization of the size-controlled catalysts, including XAS and in-situ CO-DRIFTS studies, has been performed to characterize the structure of Rh nanoparticles. Applying these catalysts to the hydroformylation of styrene, we observed that turnover frequency increases with decreasing particle size from 6.4 to 1.6 nm. When applied to hydroformylation reactions, we achieved a high branched product selectivity and successfully demonstrated a route to synthesizing the pain relief drug ibuprofen. This simple method can also synthesize Pt and Pd nanoparticles between 2–10 nm. 

Direct coupling of unactivated alcohols remains a challenge in synthetic chemistry. Current approaches to cross-coupling of alcohol-derived electrophiles often involve activated alcohols such as tosylates or carbonates. We report the direct arylative substitution of homoallylic alcohols catalyzed by a nickel-bisphosphine complex as a facile method to generate allylic arenes. These reactions proceed via formation of an allylic alcohol intermediate. Subsequent allylic substitution with arylboroxine nucleophiles enables the formation of a variety of allylic arenes. The presence of p -methoxyphenylboronic acid is crucial to activate the allylic alcohol to achieve high product yields. 

We report Ni-catalyzed dearylative cyclocondensation of aldehydes, alkynes, and triphenylborane. The reaction is initiated by oxidative cyclization of the aldehyde and alkyne coupling partners to generate an oxanickelacyclopentene which reacts with triphenylborane to form oxaboranes. This formal dearylative cyclocondensation reaction generates oxaboranes in moderate-to-high yields (47–99%) with high regioselectivities under mild reaction conditions. This approach represents a direct and modular synthesis of oxaboranes which are difficult to access using current methods. These oxaboranes are readily transformed into valuable building blocks for organic synthesis and an additional class of boron heterocycles. Selective homocoupling forms oxaboroles, oxidation generates aldol products, and reduction and arylation form substituted allylic alcohols.